Diana E Wheeler

Interests

Research

Ants, social insects, insect systems

Teaching

Insect Biology, Social Insects, Insects and Culture

Courses

Scholarly Contributions

Books

• Wheeler, D. E., Wheeler, J. N., Wheeler, G. C., Christiansen, T. A., & Lavigne, R. J. (2013). Ants of Yellowstone National Park. Create Space.

Chapters

• Hamilton, A. R., Shpigler, H., Bloch, G., Wheeler, D. E., & Robinson, G. E. (2016). Endocrine influences on insect societies. In Hormones, Brain, and Behavior 3rd edition, Volume 2(pp 421–451). Oxford: Academic Press.
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  Major review of endocrinology of social insects in a premier, 5 vol., reference series covering neurobiology primarily of vertebrates.

Journals/Publications

• Wheeler, D. E., Metzl, C., & Abouheif, E. (2017). Wilhelm Goetsch (1887-1960): Pioneering Studies on the Development and Evolution of the Soldier Caste in Social Insects. Myrmecological News.
• Corona, M., Libbrecht, R., & Wheeler, D. E. (2016). Molecular mechanisms of phenotypic plasticity in social insects. CURRENT OPINION IN INSECT SCIENCE, 13, 55-60.
• Wheeler, D. E., Buck, N. A., & Evans, J. D. (2014). Expression of insulin/insulin-like signalling and TOR pathway genes in honey bee caste determination. Insect Molecular Biology, 23(1), 113-121.
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  Abstract: The development of queen and worker castes in honey bees is induced by differential nutrition, with future queens and workers receiving diets that are qualitatively and quantitatively different. We monitored the gene expression of 14 genes for components of the insulin/insulin-like signalling and TOR pathways in honey bee larvae from 40-88 h after hatching. We compared normally fed queen and normally fed worker larvae and found that three genes showed expression differences in 40-h-old larvae. Genes that show such early differences in expression may be part of the mechanism that transduces nutrition level into a hormone signal. We then compared changes in expression after shifts in diet with those in normally developing queens and workers. Following a shift to the worker diet, the expression of 9/14 genes was upregulated in comparison with queens. Following a shift to the queen diet, expression of only one gene changed. The honey bee responses may function together as a homeostatic mechanism buffering larvae from caste-disrupting variation in nutrition. The different responses would be part of the canalization of both the queen and worker developmental pathways, and as such, a signature of advanced sociality. © 2013 The Royal Entomological Society.
• Huang, M. H., Wheeler, D. E., & Fjerdingstad, E. J. (2013). Mating system evolution and worker caste diversity in Pheidole ants. Molecular Ecology, 22(7), 1998-2010.
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  PMID: 23379584;Abstract: The efficiency of social groups is generally optimized by a division of labour, achieved through behavioural or morphological diversity of members. In social insects, colonies may increase the morphological diversity of workers by recruiting standing genetic variance for size and shape via multiply mated queens (polyandry) or multiple-breeding queens (polygyny). However, greater worker diversity in multi-lineage species may also have evolved due to mutual worker policing if there is worker reproduction. Such policing reduces the pressure on workers to maintain reproductive morphologies, allowing the evolution of greater developmental plasticity and the maintenance of more genetic variance for worker size and shape in populations. Pheidole ants vary greatly in the diversity of worker castes. Also, their workers lack ovaries and are thus invariably sterile regardless of the queen mating frequency and numbers of queens per colony. This allowed us to perform an across-species study examining the genetic effects of recruiting more patrilines on the developmental diversity of workers in the absence of confounding effects from worker policing. Using highly variable microsatellite markers, we found that the effective mating frequency of the soldier-polymorphic P. rhea (avg. me N = 2.65) was significantly higher than that of the dimorphic P. spadonia (avg. meN = 1.06), despite a significant paternity skew in P. rhea (avg. B = 0.10). Our findings support the idea that mating strategies of queens may co-evolve with selection to increase the diversity of workers. We also detected patriline bias in the production of different worker sizes, which provides direct evidence for a genetic component to worker polymorphism. © 2013 Blackwell Publishing Ltd.
• Wheeler, D. E., Buck, N., & Evans, J. (2014). Expression of insulin/insulin-like signaling and TOR pathway genes in honey bee caste determination. Insect Molecular Biology, 23(1), 113-121.
• Wheeler, D. E., Huang, M. H., & Fjerdingstadt, E. (2013). Huang, M.H. D.E. Wheeler and E.J. Fjerdingstad. Mating system evolution and worker caste diversity in Pheidole ants. Molecular Ecology 22: 1998-2010.. Molecular Ecology, 22(7), 1998-2010.
• Anderson, K. E., Russell, J. A., Moreau, C. S., Kautz, S., Sullam, K. E., Yi, H. u., Basinger, U., Mott, B. M., Buck, N., & Wheeler, D. E. (2012). Highly similar microbial communities are shared among related and trophically similar ant species. Molecular Ecology, 21(9), 2282-2296.
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  PMID: 22276952;Abstract: Ants dominate many terrestrial ecosystems, yet we know little about their nutritional physiology and ecology. While traditionally viewed as predators and scavengers, recent isotopic studies revealed that many dominant ant species are functional herbivores. As with other insects with nitrogen-poor diets, it is hypothesized that these ants rely on symbiotic bacteria for nutritional supplementation. In this study, we used cloning and 16S sequencing to further characterize the bacterial flora of several herbivorous ants, while also examining the beta diversity of bacterial communities within and between ant species from different trophic levels. Through estimating phylogenetic overlap between these communities, we tested the hypothesis that ecologically or phylogenetically similar groups of ants harbor similar microbial flora. Our findings reveal: (i) clear differences in bacterial communities harbored by predatory and herbivorous ants; (ii) notable similarities among communities from distantly related herbivorous ants and (iii) similar communities shared by different predatory army ant species. Focusing on one herbivorous ant tribe, the Cephalotini, we detected five major bacterial taxa that likely represent the core microbiota. Metabolic functions of bacterial relatives suggest that these microbes may play roles in fixing, recycling, or upgrading nitrogen. Overall, our findings reveal that similar microbial communities are harbored by ants from similar trophic niches and, to a greater extent, by related ants from the same colonies, species, genera, and tribes. These trends hint at coevolved histories between ants and microbes, suggesting new possibilities for roles of bacteria in the evolution of both herbivores and carnivores from the ant family Formicidae. © 2012 Blackwell Publishing Ltd.
• Molet, M., Wheeler, D. E., & Peeters, C. (2012). Evolution of novel mosaic castes in ants: Modularity, phenotypic plasticity, and colonial buffering. American Naturalist, 180(3), 328-341.
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  PMID: 22854076;Abstract: Many ants have independently evolved castes with novel morphology as well as function, such as soldiers and permanently wingless (ergatoid) queens. We present a conceptual model, based on modularity in morphology and development, in which evolutionary innovation is facilitated by the ancestral ant polyphenism of winged queens and wingless workers. We suggest that novel castes evolved from rare intercastes, anomalous mosaics of winged queens and workers, erratically produced by colonies through environmental or genetic perturbations. The colonial environment is highly accommodating and buffers viable intercastes from individual selection. Their cost is limited because they are diluted by the large number of nestmates, yet some can bring disproportionate benefits to their colonies in the context of defense or reproduction (e.g., wingless intercastes able to mate). Useful intercastes will increase in frequency as their morphology is stabilized through genetic accommodation. We show that both soldiers and ergatoid queens are mosaics of winged queens and workers, and they are strikingly similar to some intercastes. Modularity and developmental plasticity together with winged/wingless polyphenism thus allow for the production of highly variable mosaic intercastes, and colonies incubate the advantageous mosaics. © 2012 by The University of Chicago.
• Rajakumar, R., Mauro, D. S., Dijkstra, M. B., Huang, M. H., Wheeler, D. E., Hiou-Tim, F., Khila, A., Cournoyea, M., & Abouheif, E. (2012). Ancestral developmental potential facilitates parallel evolution in ants. Science, 335(6064), 79-82.
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  PMID: 22223805;Abstract: Complex worker caste systems have contributed to the evolutionary success of advanced ant societies; however, little is known about the developmental processes underlying their origin and evolution. We combined hormonal manipulation, gene expression, and phylogenetic analyses with field observations to understand how novel worker subcastes evolve. We uncovered an ancestral developmental potential to produce a "supersoldier" subcaste that has been actualized at least two times independently in the hyperdiverse ant genus Pheidole. This potential has been retained and can be environmentally induced throughout the genus. Therefore, the retention and induction of this potential have facilitated the parallel evolution of supersoldiers through a process known as genetic accommodation. The recurrent induction of ancestral developmental potential may facilitate the adaptive and parallel evolution of phenotypes.
• Anderson, K. E., Wheeler, D. E., Yang, K., & Linksvayer, T. A. (2011). Dynamics of an ant-ant obligate mutualism: Colony growth, density dependence and frequency dependence. Molecular Ecology, 20(8), 1781-1793.
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  PMID: 21366750;Abstract: In insect societies, worker vs. queen development (reproductive caste) is typically governed by environmental factors, but many Pogonomyrmex seed-harvester ants exhibit strict genetic caste determination, resulting in an obligate mutualism between two reproductively isolated lineages. Same-lineage matings produce fertile queens while alternate-lineage matings produce sterile workers. Because new virgin queens mate randomly with multiple males of each lineage type, and both worker and queen phenotypes are required for colony growth and future reproduction, fitness is influenced by the relative frequency of each lineage involved in the mutualistic breeding system. While models based solely on frequency-dependent selection predict the convergence of lineage frequencies towards equal (0.5/0.5), we surveyed the lineage ratios of 49 systems across the range of the mutualism and found that the global lineage frequency differed significantly from equal. Multiple regression analysis of our system survey data revealed that the density and relative frequency of one lineage decreases at lower elevations, while the frequency of the alternate lineage increases with total colony density. While the production of the first worker cohort is largely frequency dependent, relying on the random acquisition of worker-biased sperm stores, subsequent colony growth is independent of lineage frequency. We provide a simulation model showing that a net ecological advantage held by one lineage can lead to the maintenance of stable but asymmetric lineage frequencies. Collectively, these findings suggest that a combination of frequency-dependent and frequency-independent mechanisms can generate many different localized and independently evolving system equilibria. © 2011 Blackwell Publishing Ltd.
• Huang, M. H., & Wheeler, D. E. (2011). Colony demographics of rare soldier-polymorphic worker caste systems in Pheidole ants (Hymenoptera, Formicidae). Insectes Sociaux, 58(4), 539-549.
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  Abstract: Nearly all species in the ant genus Pheidole have dimorphic workers, with distinct small minors and larger soldiers. The size range of both castes is typically narrow. Just seven described species are soldier-polymorphic, with a broad soldier size range. Here, we characterize worker caste allocation and demography in the soldier-polymorphic P. obtusospinosa, P. rhea, and P. tepicana, and the dimorphic P. spadonia for comparison. The head allometry of soldiers in soldier-polymorphic species is strongly positive and that of dimorphic species is negative. Among soldier-polymorphic species, the soldier castes differ from each other in the degree of positive allometry. In addition, they differ in the number of size modes: P. obtusospinosa and P. rhea have two and P. tepicana has one. During colony ontogeny, P. obtusospinosa first has one mode and develops the second mode much later, while P. rhea produces multiple modes throughout. We also characterize worker caste systems based on the biomass allocation. For all three soldier-polymorphic species, the majority of soldiers are small soldiers. Pheidole obtusospinosa and P. rhea allocate roughly equal biomass to the two soldier classes, while P. tepicana allocates little to supersoldiers based on both biomass and caste ratio. These findings illustrate the interplay among caste ratios, biomass allocation, size frequency distributions, and allometry in the evolution of different worker caste systems. We conclude that soldier-polymorphic species may have evolved convergently in response to broad-scale factors, but differences among them suggest selection pressures in small-scale environments have been different. © 2011 International Union for the Study of Social Insects (IUSSI).
• Bloch, G., Shpigler, H., Wheeler, D. E., & Robinson, G. E. (2010). Endocrine influences on the organization of insect societies. Hormones, Brain and Behavior Online, 1027-1070.
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  Abstract: We review evidence for endocrine influences on division of labor in insect societies. Juvenile hormone (JH) has been studied most extensively. JH is involved in control of four forms of division of labor: division of labor for reproduction among adults, division of labor for reproduction via caste differentiation, division of labor for colony growth and development among adults, and division of labor for colony growth and development via physical castes. Ecdysteroids, biogenic amines, and insulin have begun to be studied in these contexts as well. Ecdysteroids are implicated in the control of caste determination and reproductive maturation in bees. Octopamine influences the division of labor among workers, octopamine and serotonin exert neurohormonal influences on the production of JH by the corpora allata, and octopamine and dopamine levels are correlated suggestively with aspects of reproductive development in bumblebees, honeybees, and paper wasps. Insulin signaling is involved in caste determination and division of labor among workers. Vitellogenin, best known as a yolk protein, may also have hormone-like functions in the regulation of division of labor among workers. We present a verbal model that proposes that evolutionary changes in endocrine function play key roles in the evolution of division of labor. © 2009 Elsevier Inc. All rights reserved.
• Curry, M. M., Wheeler, D. E., Yang, K., & Anderson, K. E. (2010). The potential for gene flow in a dependent lineage system of a harvester ant: Fair meiosis in the f₁ generation. Journal of Heredity, 101(3), 378-384.
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  PMID: 20022894;PMCID: PMC2855674;Abstract: We investigated the potential for gene flow in a dependent lineage (DL) system of the harvester ant Pogonomyrmex. Each DL system is composed of 2 reproductively isolated lineages that are locked in an obligate mutualism. The genetic components that produce the worker phenotype are acquired by hybridizing with the partner lineage. In the mating flight, queens of both lineages mate with multiple males from each lineage. During colony growth and reproduction, eggs fertilized by partner-lineage sperm produce F1 hybrid workers with interlineage genomes, whereas eggs fertilized by same-lineage sperm result in the development of new queens with intralineage genomes. New males are typically produced from unfertilized eggs laid by the pure-lineage queen but in her absence may be produced by interlineage F1 workers. We investigated the potential for interlineage gene flow in this system using 2 classes of lineage-specific nuclear markers to identify hybrid genome combinations. We confirmed the production of viable interlineage F1 reproductive females in field colonies, the occurrence of which is associated with the relative frequencies of each lineage in the population: interlineage F1 queens occurred only in the rare lineage of the population with dramatically skewed lineage frequencies. In laboratory colonies, we detected fair meiosis in interlineage F1 workers leading to the production of viable and haploid interlineage F2males. We conclude that the genomes of each lineage recombine freely, suggesting that extrinsic postzygotic selection maintains the integrity of each lineage genome. We compare our findings with those of the H1/H2 DL system. © 2009 The American Genetic Association. All rights reserved.
• Wernegreen, J. J., & Wheeler, D. E. (2009). Remaining flexible in old alliances: Functional plasticity in constrained mutualisms. DNA and Cell Biology, 28(8), 371-381.
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  PMID: 19435425;PMCID: PMC2905307;Abstract: Central to any beneficial interaction is the capacity of partners to detect and respond to significant changes in the other. Recent studies of microbial mutualists show their close integration with host development, immune responses, and acclimation to a dynamic external environment. While the significance of microbial players is broadly appreciated, we are just beginning to understand the genetic, ecological, and physiological mechanisms that generate variation in symbiont functions, broadly termed "symbiont plasticity" here. Some possible mechanisms include shifts in symbiont community composition, genetic changes via DNA acquisition, gene expression fluctuations, and variation in symbiont densities. In this review, we examine mechanisms for plasticity in the exceptionally stable mutualisms between insects and bacterial endosymbionts. Despite the severe ecological and genomic constraints imposed by their specialized lifestyle, these bacteria retain the capacity to modulate functions depending on the particular requirements of the host. Focusing on the mutualism between Blochmannia and ants, we discuss the roles of gene expression fluctuations and shifts in bacterial densities in generating symbiont plasticity. This symbiont variation is best understood by considering ant colony as the host superorganism. In this eusocial host, the bacteria meet the needs of the colony and not necessarily the individual ants that house them. © Copyright 2009, Mary Ann Liebert, Inc.
• Wheeler, D. E. (2009). Accessory Glands. Encyclopedia of Insects, 1-2.
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  Abstract: This chapter discusses accessory glands of both female and male insects. Accessory glands of reproductive systems produce secretions that aid in sperm maintenance, transport, and fertilization. In addition, accessory glands in females provide protective coatings for eggs. The interplay between male and female secretions from accessory glands is a key element in the design of diverse mating systems. Accessory gland secretions can have digestive functions important in sperm management. Sperm management by females involves a wide range of processes, including liberation of sperm from a spermatophore, digestion of male secretions and sperm, transport of sperm to and from the spermatheca, maintenance of stored sperm, and fertilization. Further, the effects of male accessory gland secretions on the female are best known for the fruit fly, Drosophila melanogaster, in which the functions of several gene products have been explored at the molecular level. Since insects have a diversity of mating systems, the specific functions of accessory gland secretions are likely to reflect this variation. © 2009 Elsevier Inc. All rights reserved.
• Wheeler, D. E. (2009). Egg Coverings. Encyclopedia of Insects, 312-313.
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  Abstract: This chapter discusses protective coverings females provide their eggs, which reflect the full range of environments exploited by insects. Egg coverings fall into two major categories: those produced by follicle cells and those produced by accessory glands of the reproductive tract. Follicle cells secrete the chorion or insect eggshell. The design of the chorion is important in fertilization, egg respiration, and water balance. Coverings produced by accessory glands provide additional protection from the elements, predators, and parasites. The vitelline envelope is considered to be the first layer of the chorion. Next, a layer of wax is secreted, giving the egg greater resistance to desiccation. Then, several more chorionic layers are produced, commonly with sheet-like inner and outer layers separated by a pillared region enclosing air spaces. The eggshell is a layer of armor protecting the egg and developing embryo from the elements, predators, and parasites. Eggshell shape, texture, and color can also provide protection through camouflage and warning coloration. © 2009 Elsevier Inc. All rights reserved.
• Wheeler, D. E. (2009). Eggs. Encyclopedia of Insects, 311-312.
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  Abstract: Typical insect eggs contain nutrients to support embryogenesis and produce newly emerged first instars. Most eggs contain large amounts of lipid, for use as building material and energy, and yolk proteins, for the amino acids needed to build a larval insect body. Eggs also contain a cytoplasmic starter kit for development that includes cellular machinery such as ribosomes. In species with symbiotic bacteria or protists, eggs are inoculated with a small population of the mutualistic microbes. Insects typically have internal fertilization, and fertilized eggs contain one set of chromosomes from each parent. Eggs are laid in protected places in environments where young are likely to find food. For example, many butterflies lay their eggs on larval food plants, mosquitoes lay their eggs in water in which larval food grows, and parasitoids lay eggs in, on, or near a host insect. Because a thin shell usually covers mature eggs, there must be a way for sperm to penetrate the shell before it is laid and a way to accommodate water balance and respiratory needs afterward. Sperms enter through an opening called the micropyle. Water and air can pass through specialized regions of the eggshell and embryonic membranes. Finally, some insect groups, remarkably, produce offspring without sperm, egg nutrients, or both. © 2009 Elsevier Inc. All rights reserved.
• Wheeler, D. E. (2009). Ovarioles. Encyclopedia of Insects, 743-744.
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  Abstract: This chapter deals with the ovarioles, an egg-producing tubules that are the fundamental units of ovaries in female insects. Each ovariole is a tube in which oocytes form at one end and complete development as they reach the other. The terminal filament and the germarium, which contains germ cells, are at the distal end. Ovarioles may have one of several topological arrangements within an ovary. In some species, ovarioles join the end of an oviduct radially around a central point. In others, ovarioles arise in single file off the oviduct, like teeth on a comb. The period during which ovarioles form varies widely in insects, ranging from embryonic development in aphids to the pupal stage in flies. In some taxa, the number of ovarioles can be adjusted on the basis of environmental factors. In Drosophila, for example, ovarioles form during the pupal period. This timing provides the opportunity for the number of ovarioles constructed to be adjusted on the basis of previous diet and temperature. In honeybees, however, ovarioles form in early larval development. The number of ovarioles formed is at first the same in future queens and workers. In workers, however, most ovarioles undergo cell death, whereas those in developing queens persist. Ovariole architecture is related to both phylogeny and life history. Both panoistic and meroistic ovarioles can support very rapid egg production as illustrated by the more than 40,000 eggs/day produced by both the panoistic ovarioles of the most fecund termite queens and the polytrophic ovarioles of the most fecund ants. © 2009 Elsevier Inc. All rights reserved.
• Wheeler, D. E. (2009). Reproduction, Female: Hormonal Control of. Encyclopedia of Insects, 882-885.
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  Abstract: This chapter focuses on the hormonal control in reproduction process of female insects. The central process in female reproduction in insects, the production of eggs, is hormonally regulated. To reproduce successfully, females must coordinate egg production with other aspects of reproduction such as dispersal, the availability of resources, and selection of mates and oviposition sites. Environmental signals are effectively translated into physiological processes by networks of hormonal signals. Egg development in insects has become a model experimental system studied to understand the general principles of stage-, sex-, and tissue-specific responses to hormones. In insects, juvenile hormone (JH) and ecdysone typically play important roles in orchestrating egg development. The development of improved analytical methods has led to the elucidation of the roles of other key hormones, particularly a variety of neurosecretory hormones. Common themes in the hormonal control of egg production are becoming clearer, as are important differences between insect groups. Hormonal control of egg production is relatively well understood in a few insects because of its use as a model system for studying hormone action. The integration of hormonal controls with other aspects of reproduction is more complex and is less well understood. © 2009 Elsevier Inc. All rights reserved.
• Wheeler, D. E. (2009). Reproduction, female. Encyclopedia of Insects, 880-882.
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  Abstract: This chapter describes the reproduction process in female insects. In female insects, reproduction generally involves producing yolky eggs, mating, and then laying fertilized eggs. Across the diversity of insects, however, different ways of reproducing illustrate an astounding variation in this simple series of events as well as divergence from it. In the most extreme examples, females can reproduce without supplying eggs with yolk, without mating, and even without laying eggs. Frequent confrontations between humans and insects in the arenas of agriculture and health make understanding insect reproduction of great practical importance. Production of the next generation of insects has several steps that are centered on the female. To reproduce, females need to make eggs or provide their embryos with nutrition in other ways. Once made, females must find an appropriate spot to deposit their eggs. For entomologists concerned with problem insects, these steps offer opportunities to disrupt reproduction and reduce the number of insects in the next generation. Second, the diversity of ways that insects reproduce provides a rich source of material for discovering the underlying rules of biology. For example, the extraordinary effectiveness of female insects in converting resources into eggs led to their use as an intensively studied model system. The process by which yolk is taken up into insect eggs serves as a model for how cells take up large molecules from the surrounding environment. © 2009 Elsevier Inc. All rights reserved.
• Johnston, M. L., & Wheeler, D. E. (2007). The role of storage proteins in colony-founding in termites. Insectes Sociaux, 54(4), 383-387.
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  Abstract: Hexameric storage proteins are widespread in insects and provide a source of amino acids when demand is high and intake is limited, such as during metamorphosis. We investigated the occurrence of storage protein levels in alates and in colony founding pairs in a dry-wood nesting species and two soil-nesting species of termites. Females and males contained similar quantities of storage protein at the time of the mating flight. Alates of soil-nesting species contained much higher levels of storage protein than the wood nesting species. After eggs hatched, protein stores plummeted in both sexes of both ecological types. Greater storage by alates of soil-nesting species is correlated with lack of access food during founding and the larger number of workers produced in their first broods. © 2007 Birkhaeuser.
• Weinstock, G. M., Robinson, G. E., Gibbs, R. A., Worley, K. C., Evans, J. D., Maleszka, R., Robertson, H. M., Weaver, D. B., Beye, M., Bork, P., Elsik, C. G., Hartfelder, K., Hunt, G. J., Zdobnov, E. M., Amdam, G. V., M., M., Collins, A. M., Cristino, A. S., Michael, H., , Lobo, C. H., et al. (2006). Insights into social insects from the genome of the honeybee Apis mellifera. Nature, 443(7114), 931-949.
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  PMID: 17073008;PMCID: PMC2048586;Abstract: Here we report the genome sequence of the honeybee Apis mellifera, a key model for social behaviour and essential to global ecology through pollination. Compared with other sequenced insect genomes, the A. mellifera genome has high A+T and CpG contents, lacks major transposon families, evolves more slowly, and is more similar to vertebrates for circadian rhythm, RNA interference and DNA methylation genes, among others. Furthermore, A. mellifera has fewer genes for innate immunity, detoxification enzymes, cuticle-forming proteins and gustatory receptors, more genes for odorant receptors, and novel genes for nectar and pollen utilization, consistent with its ecology and social organization. Compared to Drosophila, genes in early developmental pathways differ in Apis, whereas similarities exist for functions that differ markedly, such as sex determination, brain function and behaviour. Population genetics suggests a novel African origin for the species A. mellifera and insights into whether Africanized bees spread throughout the New World via hybridization or displacement. ©2006 Nature PublishingGroup.
• Wheeler, D. E., Buck, N., & Evans, J. D. (2006). Expression of insulin pathway genes during the period of caste determination in the honey bee, Apis mellifera. Insect Molecular Biology, 15(5), 597-602.
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  PMID: 17069635;PMCID: PMC1761130;Abstract: Female honeybees have two castes, queens and workers. Developmental fate is determined by larval diet. Coding sequences made available through the Honey Bee Genome Sequencing Consortium allow for a pathway-based approach to understanding caste determination. We examined the expression of several genes of the insulin signalling pathway, which is central to regulation of growth based on nutrition. We found one insulin-like peptide expressed at very high levels in queen but not worker larvae. Also, the gene for an insulin receptor was expressed at higher levels in queen larvae during the 2nd larval instar. These results demonstrate that the insulin pathway is a compelling candidate for pursing the relationship between diet and downstream signals involved in caste determination and differentiation. © 2006 The Authors.
• A., M., Isoe, J., Wheeler, D. E., & Wells, M. A. (2005). Evolution of insect metamorphosis: A microarray-based study of larval and adult gene expression in the ant Camponotus festinatus. Evolution, 59(4), 858-870.
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  PMID: 15926695;Abstract: Holometabolous insects inhabit almost every terrestrial ecosystem. The evolutionary success of holometabolous insects stems partly from their developmental program, which includes discrete larval and adult stages. To gain an understanding of how development differs among holometabolous insect taxa, we used cDNA microarray technology to examine differences in gene expression between larval and adult Camponotus festinatus ants. We then compared expression patterns obtained from our study to those observed in the fruitfly Drosophila melanogaster. We found that many genes showed distinct patterns of expression between the larval and adult ant life stages, a result that was confirmed through quantitative reverse-transcriptase polymerase chain reaction. Genes involved in protein metabolism and possessing structural activity tended to be more highly expressed in larval than adult ants. In contrast, genes relatively upregulated in adults possessed a greater diversity of functions and activities. We also discovered that patterns of expression observed for homologous genes in D. melanogaster differed substantially from those observed in C. festinatus. Our results suggest that the specific molecular mechanisms involved in metamorphosis will differ substantially between insect taxa. Systematic investigation of gene expression during development of other taxa will provide additional information on how developmental pathways evolve. © 2005 The Society for the Study of Evolution. All rights reserved.
• Cassill, D. L., Butler, J., Vinson, S. B., & Wheeler, D. E. (2005). Cooperation during prey digestion between workers and larvae in the ant, Pheidole spadonia. Insectes Sociaux, 52(4), 339-343.
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  Abstract: Digestion and distribution of nutrients are central to the growth and reproduction of social insect colonies, just as they are to individual organisms. In the case of eusocial insect species, different components of food handling and processing can be distributed among castes. This paper reports on an ant species, Pheidole spadonia, in which the adult workers butcher prey and 4th instar larvae dissolve prey for distribution among other colony members including workers, larvae and queens. To characterize the process, six groups, each composed of twenty-five workers and thirty larvae, were provisioned with a fruit fly carcass, and then video-taped continuously for 24 hours. On average, five adult workers and twenty-two 4th instar larvae invested 12.8 labor hours into butchering and predigesting one fly carcass. Workers contributed a mean total of 3.3 labor hours to butcher the carcass into small fragments. Fourth instar larvae contributed a mean total of 9.5 labor hours to pre-orally dissolve the solid fragments. Surprisingly, larvae did not ingest during the dissolving process. Instead, workers ingested the dissolved prey tissue into their crops and then regurgitated it to colony members, larvae and workers, that solicited for feedings. The cooperative interactions reported here between workers and larvae extend the mechanistic and evolutionary explanations for eusociality. © Birkhäuser Verlag, 2005.
• Hahn, D. A., Johnson, R. A., Buck, N. A., & Wheeler, D. E. (2004). Storage protein content as a functional marker for colony-founding strategies: A comparative study within the harvester ant genus Pogonomyrmex. Physiological and Biochemical Zoology, 77(1), 100-108.
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  PMID: 15057720;Abstract: Claustral colony founding, in which new queens rear their first clutch of workers solely from internal reserves, is common in the higher ant subfamilies and is believed to represent a major innovation in ant life histories. The ability to store large amounts of amino acids contained in storage proteins is an essential physiological trait for claustral colony founding by ant queens. To determine whether there is an association between storage protein content and colony-founding strategy, we identified and quantified two major storage proteins in queens of five harvester ant species in the genus Pogonomyrmex that differ in colony-founding strategy. Queens of the fully claustral non-foraging species Pogonomyrmex rugosus and Pogonomyrmex maricopa contained the greatest amount of these proteins. Facultatively foraging semiclaustral Pogonomyrmex occidentalis queens contained an intermediate amount. Obligately foraging semiclaustral Pogonomyrmex californicus queens from two different populations contained significantly less storage protein than the other independent-founding species. Queens of the dependent-founding social parasite Pogonomyrmex anergismus also contained little storage protein. Our results suggest that storage protein content has evolved in concert with colony-founding strategies in the genus Pogonomyrme and provides a good functional marker for colony-founding strategy.
• Hahn, D. A., & Wheeler, D. E. (2003). Presence of a single abundant storage hexamerin in both larvae and adults of the grasshopper, Schistocerca americana. Journal of Insect Physiology, 49(12), 1189-1197.
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  PMID: 14624891;Abstract: We identified a single hexameric storage protein in the grasshopper, Schistocerca americana, and monitored its abundance through the last larval instar and up until reproductive competence in adults of both sexes. This storage hexamerin, termed Schistocerca americana Persistent Storage Protein (saPSP) was the most abundant soluble protein in both larvae and adults. In both sexes, saPSP abundance started out low at the onset of the last larval instar and accumulated during feeding, peaking just prior to molting. Adults of both sexes contained significant amounts of saPSP after eclosion. In adult males, saPSP content dropped continuously after eclosion and was lowest once individuals reached reproductive maturity. In contrast, adult females depleted saPSP reserves during the first days of adulthood, but subsequently accumulated significant saPSP stores. In adult females, saPSP stores peaked just prior to the completion of egg provisioning. Given the overall patterns of abundance, saPSP has functions in both larvae and adults. In addition, the observed pattern of storage hexamerin accumulation differs from patterns of accumulation in the other known grasshoppers, Locusta migratoria and Romalea microptera, suggesting that significant functional diversity has evolved in storage hexamerins among the grasshoppers. © 2003 Elsevier Ltd. All rights reserved.
• Hunt, J. H., Buck, N. A., & Wheeler, D. E. (2003). Storage proteins in vespid wasps: Characterization, developmental pattern, and occurrence in adults. Journal of Insect Physiology, 49(8), 785-794.
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  PMID: 12880659;Abstract: Wasps of family Vespidae contain three types of major proteins that have the size, amino acid composition, subunit composition, immunological reactivity, and pattern of occurrence characteristic of storage proteins. The three types of storage protein, which have been identified in other Hymenoptera, are very high density lipoprotein, high glutamine/glutamic acid protein, and hexamerin. The predominant pattern of occurrence for these proteins is as known from most or all Holometabola: synthesis during the last larval instar and utilization as an amino acid source during metamorphosis. Hexamerin also occurred in a large young adult female Monobia quadridens but not a small one, which suggests that carry-over into adult females is a reaction norm response to quantity of larval provisions, because these wasps could not have fed as adults. In two paper wasp species of the genus Polistes, hexamerin was present in large adult females which emerged during the colony cycle phase when reproductive females are typically produced, but not in adult female offspring that emerged earlier in the colony cycle or in adult females that were workers. It cannot be confirmed by these data that the hexamerin in the adult paper wasps represented carry-over from metamorphosis rather than post-emergence feeding, but the pattern of occurrence suggests that presence of storage protein may play a role in caste differentiation in paper wasps. No storage protein was found in any adult Vespula maculifrons, a yellowjacket wasp, suggesting that caste differentiation in vespine wasps does not incorporate storage protein as a component. © 2003 Elsevier Ltd. All rights reserved.
• Telang, A., Buck, N. A., Chapman, R. F., & Wheeler, D. E. (2003). Sexual differences in postingestive processing of dietary protein and carbohydrate in caterpillars of two species. Physiological and Biochemical Zoology, 76(2), 247-255.
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  PMID: 12794678;Abstract: Previous studies indicated that female Heliothis virescens and Estigmene acrea caterpillars use both feeding and postingestive processing as mechanisms to meet nutrient demands. We present utilization and nutrient budget data on the postingestive partitioning of nutrients into pre- and postabsorptive components. Both species utilized carbohydrate efficiently except at very high ingestion rates. Of the carbohydrate utilized, more was unaccounted for as intake increased, and we assume the material unaccounted for served as a respiratory substrate. In contrast, the pattern of nitrogen utilization differed between the species. Larval H. virescens efficiently retained nitrogen except at very high ingestion rates, whereas E. acrea progressively increased nitrogen egestion in response to increased nitrogen ingestion. Overall, females of both species utilized nitrogen more efficiently than did males at most ingestion levels, thus contributing to the greater protein-derived growth we previously reported. In addition, for H. virescens, protein and amino acids accounted for a small proportion of fecal nitrogen so that most of the fecal nitrogen was of a postabsorptive nature. In contrast, nitrogen excreted by E. acrea could be partitioned into both pre- and postabsorptive components. The manner of postingestive processing by these two species reflects differences in their larval diet.
• Wheeler, D. E., & Nijhout, H. F. (2003). A perspective for understanding the modes of juvenile hormone action as a lipid signaling system. BioEssays, 25(10), 994-1001.
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  PMID: 14505366;Abstract: The juvenile hormones of insects regulate an unusually large diversity of processes during postembryonic development and adult reproduction. It is a long-standing puzzle in insect developmental biology and physiology how one hormone can have such diverse effects. The search for molecular mechanisms of juvenile hormone action has been guided by classical models for hormone-receptor interaction. Yet, despite substantial effort, the search for a juvenile hormone receptor has been frustrating and has yielded limited results. We note here that a number of lipid-soluble signaling molecules in vertebrates, invertebrates and plants show curious similarities to the properties of juvenile hormones of insects. Until now, these signaling molecules have been thought of as uniquely evolved mechanisms that perform specialized regulatory functions in the taxon where they were discovered. We show that this array of lipid signaling molecules share interesting properties and suggest that they constitute a large set of signal control and transduction mechanisms that include, but range far beyond, the classical steroid hormone signaling mechanism. Juvenile hormone is the insect representative of this widespread and diverse system of lipid signaling molecules that regulate protein activity in a variety of ways. We propose a synthetic perspective for understanding juvenile hormone action in light of other lipid signaling systems and suggest that lipid activation of proteins has evolved to modulate existing signal activation and transduction mechanisms in animals and plants. Since small lipids can be inserted into many different pathways, lipid-activated proteins have evolved to play a great diversity of roles in physiology and development. © 2003 Wiley Periodicals, Inc.
• Hahn, D. A., & Wheeler, D. E. (2002). Seasonal foraging activity and bait preferences of ants on Barro Colorado Island, Panama. Biotropica, 34(3), 348-356.
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  Abstract: A yearlong arboreal baiting survey of ants was conducted during 1983 on Barro Colorado Island, Panama. Because of a severe El Niño event, the 1983 dry season in Panama was exceptionally long and dry with a distinct boundary between the dry and wet seasons. Baits, located on tree trunks, attracted both terrestrial and arboreal ants, allowing comparisons between the two groups. Species composition at baits changed dramatically with season. Baits were primarily occupied by arboreal species during the dry season, while wet season baits were occupied mostly by terrestrial species. Arboreal and terrestrial ants differed markedly in their preferences for protein- or carbohydrate-based baits; arboreal ants preferred protein-based baits and terrestrial ants preferred carbohydrate-based baits. Foraging preference for protein suggests that protein resources were limiting for arboreal ants, particularly during the dry season, and that carbohydrate resources were limiting for terrestrial ants. Fundamental differences in arboreal and terrestrial habitats may promote the differences in foraging strategies observed during an annual cycle in a seasonal tropical forest.
• Telang, A., Buck, N. A., & Wheeler, D. E. (2002). Response of storage protein levels to variation in dietary protein levels. Journal of Insect Physiology, 48(11), 1021-1029.
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  Abstract: Storage proteins have been found to play a major role in insect metamorphosis and egg production and are accumulated during the actively feeding larval stage. Yet few studies have focused on how nutrition affects storage protein levels. Three storage proteins were identified in male and female Heliothis virescens pupae, one arylphorin and two putative high-methionine hexamers. Storage proteins were quantified in early pupae and in pharate adults. Storage protein levels peaked in 48-h pupae and were more abundant in females across all stages. Both male and female pharate adults retained a portion of total storage protein levels and females retained greater levels overall. In females, post-eclosion protein reserves will likely be used toward egg manufacturing, while the role of protein reserves in males remains speculative. In our previous study of H. virescens larvae, we found that protein-derived growth in females progressively increased as dietary protein levels increased. Our present data show that levels of storage protein also increased progressively along with dietary protein levels. This suggests that females allocated protein, in excess of adult tissue formation needs, toward storage protein. Our study is the first to demonstrate how responsive storage protein levels can be in face of varying levels of dietary protein. © 2002 Elsevier Science Ltd. All rights reserved.
• Evans, J. D., & Wheeler, D. E. (2001). Expression profiles during honeybee caste determination.. Genome biology, 2(1), RESEARCH0001.
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  PMID: 11178278;PMCID: PMC17597;Abstract: BACKGROUND: Depending on their larval environment, female honeybees develop into either queens or workers. As in other polyphenisms, this developmental switch depends not on genomic differences between queens and workers but on the differential expression of entire suites of genes involved with larval fate. As such, this and other polyphenic systems can provide a novel tool for understanding how genomes and environmental conditions interact to produce different developmental trajectories. Here we use gene-expression profiles during honeybee caste determination to present the first genomic view of polyphenic development. RESULTS: Larvae raised as queens or workers differed greatly in their gene-expression patterns. Workers remained more faithful than queens to the expression profiles of younger, bipotential, larvae. Queens appeared to both downregulate many of the genes expressed by bipotential larvae and turn on a distinct set of caste-related genes. Queens overexpressed several metabolic enzymes, workers showed increased expression of a member of the cytochrome P450 family, hexameric storage proteins and dihydrodiol dehydrogenase, and young larvae overexpressed two putative heat-shock proteins (70 and 90 kDa), and several proteins related to RNA processing and translation. CONCLUSIONS: Large differences in gene expression between queens and workers indicate that social insect castes have faced strong directional selection pressures. Overexpression of metabolic enzymes by queen-destined larvae appears to reflect the enhanced growth rate of queens during late larval development. Many of the differently expressed genes we identified have been tied to metabolic rates and cellular responses to hormones, a result consistent with known physiological differences between queen and worker larvae.
• Evans, J. D., & Wheeler, D. E. (2001). Gene expression and the evolution of insect polyphenisms. BioEssays, 23(1), 62-68.
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  PMID: 11135310;Abstract: Polyphenic differences between individuals arise not through differences at the genome level but as a result of specific cues received during development. Polyphenisms often involve entire suites of characters, as shown dramatically by the polyphenic castes found in many social insect colonies. An understanding of the genetic architecture behind polyphenisms provides a novel means of studying the interplay between genomes, gene expression and phenotypes. Here we discuss polyphenisms and molecular genetic tools now available to unravel their developmental bases in insects. We focus on several recent studies that have tracked gene-expression patterns during social insect caste determination. BioEssays 23:62-68, 2001. Published 2001 John Wiley & Sons, Inc.
• Telang, A., Booton, V., Chapman, R. F., & Wheeler, D. E. (2001). How female caterpillars accumulate their nutrient reserves. Journal of Insect Physiology, 47(9), 1055-1064.
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  Abstract: Female Lepidoptera are often heavier than males. We examined the importance of consumption and post-ingestive processing as mechanisms for female Heliothis virescens larvae to meet the protein and carbohydrate requirements. In experiments in which caterpillars had a choice of diets, enabling them to select an appropriate protein and carbohydrate intake, females caterpillars ate more carbohydrate than males, but only on the heavily carbohydrate biased treatment. Overall, the sexes were not distinguished according to the selective feeding behavior, but females accumulated more protein and carbohydrate over the whole instar than the males did. Additionally, when given no choice, females ate more than males and accumulated more protein provided the diet contained a high proportion of protein. If they were reared on a high carbohydrate diet, there were no differences between the sexes. Our results indicate that female H. virescens larvae accumulate protein by regulating both intake and post-ingestive processing on high protein foods. In the field, late instar H. virescens feed on anthers, which are protein-rich and have the highest amino acid content relative to other cotton floral tissues. © 2001 Elsevier Science Ltd.
• Zakharkin, S. O., Headley, V. V., Kumar, N. K., Buck, N. A., Wheeler, D. E., & Beneš, H. (2001). Female-specific expression of a hexamerin gene in larvae of an autogenous mosquito. European Journal of Biochemistry, 268(22), 5713-5722.
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  PMID: 11722555;Abstract: Fourth-instar larvae of the autogenous mosquito, Aedes atropalpus, synthesize three hexamerins or hexameric storage proteins which are distinguished by different methionine and aromatic amino-acid contents. One protein, Hexamerin-1.2 (AatHex-1.2) is only found in female larvae and pupae. In order to investigate the molecular basis for this sex-specific accumulation, we have cloned and sequenced the cDNA encoding AatHex-1.2 and isolated and sequenced over 1 kb of the 5′ flanking region of the AatHex-1.2 gene. The AatHex-1.2 transcript encodes a 81.6-kDa hexamerin subunit which contains 19.8% phenylalanine, tyrosine and tryptophan and 8.6% methionine residues. The single-copy AatHex-1.2 gene consists of three exons and two small introns located at its 5′ end. A 2.3-kb AatHex-1.2 mRNA accumulates only in female larvae and pupae and is expressed at very low levels in adult female mosquitoes. The temporal expression profile of this transcript is typical of other mosquito hexamerin genes, with rapid disappearance of the mRNA shortly after pupation. Hence this is the first observation of exclusively female-specific gene activity during preadult development of an insect. In the 5′ flanking region of the AatHex-1.2 gene, we identified putative binding sites for transcription factors, such as GATA, C/EBP and Doublesex, typically involved in fat body- and female-specific gene activity in Diptera. These findings suggest that mechanisms for sex-specific transcription in the fat body may be well conserved between flies and mosquitoes.
• Evans, J., Degrandi-Hoffman, G., & Wheeler, D. (2000). Honey bee queen production: Tight genes or too much food?. American Bee Journal, 140(2), 136-137.
• Martínez, T., Burmester, T., Veenstra, J. A., & Wheeler, D. (2000). Sequence and evolution of a hexamerin from the ant Camponotus festinatus. Insect Molecular Biology, 9(4), 427-431.
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  PMID: 10971720;Abstract: In the ant Camponotus festinatus, two different hexamerins accumulate stage-specifically during the late larval period and at various times in adults. These hexamerins serve as storage proteins and play important roles in brood nourishment and colony founding. We report an analysis of the cDNA sequence of C. festinatus hexamerin 2 (CfeHex2). The native protein contains 732 amino acids, which are moderately enriched in aromatic amino acids, aspartate and asparagine. Phylogenetic analyses show a close relationship of CfeHex2 to a putative toxin of the braconid wasp, Bracon hebetor. The divergence of Formicidae and Braconidae hexamerins was calculated to have begun 187 MYA, an estimate consistent with currently accepted phylogeny of insect orders.
• Wheeler, D. (2000). Annual Review of Entomology: Preface. Annual Review of Entomology, 45, x-xi.
• Wheeler, D. E., Tuchinskaya, I., Buck, N. A., & Tabashnik, B. E. (2000). Hexameric storage proteins during metamorphosis and egg production in the diamondback moth, Plutella xylostella (Lepidoptera). Journal of Insect Physiology, 46(6), 951-958.
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  Abstract: As in many Lepidoptera, Plutella xylostella adults do not feed on protein and females must use accumulated reserves to supply vitellogenin synthesis. Storage proteins were quantified in females and males from the late larval stage through day 4 of adult life. The level of storage protein peaked in the early pupal stage, with females having about twice as much as males. In males, the level fell through pupal development and dropped to a trace by one day after eclosion. In females, level of storage proteins fell until eclosion, and then rose dramatically within four hours after the molt to about 2/3 of the original peak level. This post-eclosion increase, which has not been reported previously in insects, suggests that adult females synthesize hexamerins to resequester amino acids. Subsequently, the level of storage proteins fell as vitellogenin appeared and eggs were laid. The ability to synthesize and sequester amino acids as storage proteins during the adult stage has wide-ranging implication for protein management in insects, particularly those that are long-lived and have flexible schedules of reproduction. (C) 2000 Elsevier Science Ltd.
• Atmowidjojo, A. H., Erickson, E. H., Wheeler, D. E., & Cohen, A. C. (1999). Regulation of hemolymph osmolality in feral and domestic honeybees, Apis mellifera L. (Hymenoptera: Apidae). Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology, 122(2), 227-233.
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  Abstract: Experiments were conducted to compare the ability of unmanaged fetal and managed domestic honeybees in the arid Southwest to regulate hemolymph solutes, osmolality, and uric acid. Honeybees from feral and domestic colonies were desiccated (at 30°C and 0% humidity) for 2 h with undesiccated bees held as controls. Hemolymph osmolality, proteins, amino acid, and uric acid concentrations were analyzed. Hemolymph osmotic pressures of desiccated feral bees were significantly lower than those of domestic honeybees (P < 0.004). There was a significant difference in hemolymph protein concentrations between undesiccated and desiccated honeybees (P < 0.001). The hemolymph concentration of amino acids was significantly higher in undesiccated bees than in desiccated honeybees (P < 0.0031). There were no differences in uric acid concentrations between feral and domestic bees, and between desiccated and undesiccated honeybees. Hence, differences in temperature tolerance and water balance between feral and domestic honey bees are not explained by differential regulation of hemolymph osmolality, proteins, or free amino acids, or by regulation of uric acid excretion.
• Evans, J. D., & Wheeler, D. E. (1999). Differential gene expression between developing queens and workers in the honey bee, Apis mellifera. Proceedings of the National Academy of Sciences of the United States of America, 96(10), 5575-5580.
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  PMID: 10318926;PMCID: PMC21902;Abstract: Many insects show polyphenisms, or alternative morphologies, which are based on differential gene expression rather than genetic polymorphism. Queens and workers are alternative forms of the adult female honey bee and represent one of the best known examples of insect polyphenism. Hormonal regulation of caste determination in honey bees has been studied in detail, but little is known about the proximate molecular mechanisms underlying this process, or any other such polyphenism. We report the success of a molecular- genetic approach for studying queen- and worker-specific gene expression in the development of the honey bee (Apis mellifera). Numerous genes appear to be differentially expressed between the two castes. Seven differentially expressed loci described here belong to at least five distinctly different evolutionary and functional groups. Two are particularly promising as potential regulators of caste differentiation. One is homologous to a widespread class of proteins that bind lipids and other hydrophobic ligands, including retinoic acid. The second locus shows sequence similarity to a DNA- binding domain in the Ets family of transcription factors. The remaining loci appear to be involved with downstream changes inherent to queen- or worker- specific developmental pathways. Caste determination in honey bees is typically thought of as primarily queen determination; our results make it clear that the process involves specific activation of genes in workers as well as in queens.
• Wetterer, J. K., Miller, S. E., Wheeler, D. E., Olson, C. A., Polhemus, D. A., Pitts, M., Ashton, I. W., Himler, A. G., Yospin, M. M., Helms, K. R., Harken, E. L., Gallaher, J., Dunning, C. E., Nelson, M., Litsinger, J., Southern, A., & Burgess, T. L. (1999). Ecological dominance by Paratrechina longicornis (Hymenoptera: Formicidae), an invasive tramp ant, in biosphere 2. Florida Entomologist, 82(3), 381-388.
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  Abstract: Tramp ants are invading disturbed ecosystems worldwide, exterminating untold numbers of native species. They have even invaded Biosphere 2, a 1.28-hectare closed greenhouse structure built in the Arizona desert as a microcosm for studying ecological interactions and global change. Invertebrate surveys within Biosphere 2 from 1990 to 1997 have revealed dramatic changes in faunal composition, including an almost complete replacement of the ant fauna by a single tramp ant species. In 1990-91, surveys in Biosphere 2 found no one ant species dominant. By 1993, populations of the crazy ant, Paratrechina longicornis (Latreille), a tramp species not found in 1990-91, had increased to extremely high levels. In 1996, virtually all ants (>99.9%) coming to bait were P. longicornis. We observed P. longicornis foragers feeding almost exclusively on the sugary excretions (honeydew) produced by vast numbers of Homoptera, primarily scale insects and mealybugs, found on many of the plants. High densities of ants were associated with high densities of homopterans. In 1997, soil and litter surveys found that the only invertebrates thriving in Biosphere 2, besides P. longicornis and homopterans, were either species with effective defenses against ants (well-armored isopods and millipedes) or tiny subterranean species that can escape ant predation (mites, thief ants, and springtails). A convergent pattern of biodiversity occurs in disturbed tropical and subtropical ecosystems dominated by tramp ants.
• Wheeler, D., Liebig, J., & Hölldobler, B. (1999). Atypical vitellins in ponerine ants (Formicidae: Hymenoptera). Journal of Insect Physiology, 45(3), 287-293.
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  Abstract: Higher hymenopteran vitellogenin/vitellins have been characterized as containing one large apoprotein. We show that in the ant subfamily Ponerinae, species in the tribes Odontomachini, Platythyrini, and Amblyoponini, also have a vitellin with this simple structure, containing a single apoprotein of 180-190 kDa. Species in tribes Ponerini and Ectatommini, however, have vitellins containing multiple subunits. The size and number of the subunits varies, with differences even among species within the same genus. This is the first report of diversity in vitellogenin structure in the higher Hymenoptera. Vitellin and vitellogenin in Harpegnathos saltator (Ponerini) contain two large subunits of about 165 kDa and two small subunits of about 45 and 43 kDa. N-terminal sequence analysis suggests that provitellogenin is cleaved at two different sites, producing two large and two small subunits differing slightly in size. Diversity of vitellin types in Ponerini and Ectatommini is similar to that found in the more primitive tenthredinoid sawflies (Hymenoptera, Symphyta), and may indicate polyphyly in the Ponerinae. Insect vitellogenins and yolk proteins show considerably more diversity than originally believed, and the possibility of the functional significance of these differences should be considered.
• Atmowidjojo, A. H., Wheeler, D. E., Erickson, E. H., & Cohen, A. C. (1997). Temperature tolerance and water balance in feral and domestic honey bees, Apis mellifera L.. Comparative Biochemistry and Physiology - A Physiology, 118(4), 1399-1403.
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  Abstract: Feral and domestic honey bees were compared to determine relative levels of adaptation to the Arizona desert. Feral honey bees were more tolerant to high temperatures than domestic honey bees. Monthly critical thermal maxima (CTMs) of fetal bees were significantly different from those of domestic bees (P < 0.001). The highest mean CTM for feral bees was 50.7 ± 1.0°C, and for domestic honey bees was 42.8 ± 2.8°C; both were recorded in June 1991. There was also a significant effect of sampling date on CTMs (P < 0.0001). Water loss increased with increasing temperature and with decreasing humidity for both feral and domestic honey bees. The rates of water loss for both types of bees were highest in dry air (0% relative humility) at 35°C, with the average value of 6.82 ± 0.33 mg/g/hr for domestic bees. At 35°C, the rate of water loss of feral bees was more than twice that at 25°C (5.94 compared with 2.37 mg/g/hr). Water losses for feral and domestic honey bees were not significantly different; therefore, rates of water loss do not explain the higher temperature tolerance of feral honey bees.
• Roche, R. K., & Wheeler, D. E. (1997). Morphological specializations of the digestive tract of Zacryptocerus rohweri (Hymenoptera: Formicidae). Journal of Morphology, 234(3), 253-262.
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  Abstract: Light, scanning, and transmission electron microscopy are used to examine the morphology and ultrastructure of the peculiar digestive tract of the turtle ant, Zacryptocerus rohweri. The proventriculus is heavily sclerotized and covered with clusters of small spines. Narrow spine-lined channels converging at the opening to the midgut act as a fine filter of food; particles >12.5 μm are unable to pass through the proventriculus. In the midgut, ultrastructural study reveals bacteria among the microvilli of midgut epithelial cells. The hindgut of Z. rohweri consists of an enlarged, dark-colored pouch filled with masses of bacteria of three major morphotypes. A thick layer of circular muscle and deep infoldings of the epithelium greatly increase surface area for absorption. Newly emerged individuals appear to acquire these microorganisms by soliciting material from the abdomen tip of other older workers in the colony. Whether or not the hindgut bacteria are true symbionts is unknown; their acquisition and presence suggest that they may supplement the ants' limited, liquid diet by supplying essential amine acids and other nutrients.
• Nijhout, H. F., & Wheeler, D. E. (1996). Growth models of complex allometries in holometabolous insects. American Naturalist, 148(1), 40-56.
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  Abstract: Allometries among body parts of adult holometabolous insects differ from allometries among body parts of many other animals because adult structures (many of which are derived from imaginal disks) do not grow synchronously with the body. Imaginal structures grow little during larval life but experience most of their growth during the prepupal and pupal period, after food intake and somatic growth have ceased. Growth of imaginal tissues thus occurs in a closed system at the expense of nutrients accumulated during larval life. In a closed system, growing imaginal tissues compete for available nutrients, and the growth trajectory and final size of one tissue (or disk) are influenced by the growth of others. We use the Gompertz growth equation and a model of growth in a closed system in which imaginal disks compete for nutrients to model the growth of imaginal disks and the resulting allometric relations among them. By incorporating known features of ant caste development, such as reprogramming of the critical size for metamorphosis in major workers (soldiers) and reprogramming of developmental parameters in individuals larger than a critical size, we show that the nonlinear and discontinuous allometries of ants with polymorphic castes result from normal developmental processes during the metamorphosis of holometabolous insects. The imaginal disk competition model predicts that when one disk is reprogrammed, others will show a compensatory response. Such correlated developmental responses may play a role in the evolution of body proportions in ants, rhinoceros beetles, and other insects.
• Reichardt, A. K., & Wheeler, D. E. (1996). Multiple mating in the ant Acromyrmex versicolor: A case of female control. Behavioral Ecology and Sociobiology, 38(4), 219-225.
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  Abstract: In eusocial insects, polyandrous mating has the potential to reduce genetic relatedness of individuals within a colony, which may have a profound effect on the stability and social structure of the colony. Here we present evidence that multiple mating is common in both males and females of the desert leaf-cutter ant Acromyrmex versicolor. Females seem to have complete control over the number of matings, and mate on average with three males, even though the sperm transferred in a single copulation is sufficient to fill the spermatheca. To determine whether there is a bias in the representation of sperm from different mates in the spermatheca, females were mated to three or four males in controlled mating experiments and were subsequently allowed to found colonies in the laboratory. Paternity analysis of the offspring by random amplified polymorphic DNA analysis showed that all males that have been mated to a female successfully contributed sperm to the production of her offspring. No significant asymmetry in sperm use was detected, suggesting complete sperm mixing. Different hypotheses to explain polyandrous mating are discussed, and it is argued that the best hypothesis to explain polyandrous mating and complete sperm mixing in A. versicolor is that utilizing genetically diverse sperm confers a selective advantage on females.
• Wheeler, D. (1996). The role of nourishment in oogenesis. Annual Review of Entomology, 41(1), 407-431.
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  PMID: 15012335;Abstract: Oogenesis in insects is typically a nutrient-limited process, triggered only if sufficient nourishment is available. This nourishment can be acquired during the larval or adult stage, depending on the insect. Timing of food intake will have major effects on mechanisms of hormonal control. When nourishment for eggs is taken primarily by adults, insufficient nutrition inhibits egg development through mechanisms such as inhibition of corpora allata, as seen in Orthoptera and Blattaria. In adult Diptera, lack of protein inhibits release of brain factors that produce reproductive competency or ovarian stimulation. Lepidoptera have been characterized as lacking substantial regulation of oogenesis because egg development is well under way at emergence. Many species for which ecological data are available do not mobilize reserves carried over from the larval stage until they feed as adults. The endocrine mechanisms underlying these systems are poorly understood. In many insects, mating and activity can affect nutritional state and therefore oogenesis. Mating can stimulate oogenesis through mobilization of reserves or through nutritional contributions by males to females. Activity, especially flight, and oogenesis can compete for energy. The flight apparatus, especially the muscle, can also compete with oogenesis for protein. Social insects exhibit extreme specializations in oogenesis; females range in fertility from completely sterile to hyperfecund. Food flow within colonies is a major factor regulating fecundity. Finally, maternal nourishment is not needed for oogenesis in parasitoids and pseudoplacental viviparous insects, which produce eggs with little or no yolk. Virtually nothing is known about the endocrine regulation of oogenesis in these insects.
• Wheeler, D. (1996). The role of nourishment in oogenesis. Annual review of entomology. Vol. 41, 407-431.
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  Abstract: Oogenesis in insects is triggered only if sufficient nourishment is available. This nourishment can be acquired during the larval or adult stage. When nourishment for eggs is taken primarily by adults, insufficient nutrition inhibits egg development through mechanisms such as inhibition of corpora allata, as seen in Orthopotera and Blattaria. In adult Diptera, lack of protein inhibits release of brain factors that produce reproductive competency or ovarian stimulation. Mating can stimulate oogenesis through mobilization of reserves or through nutritional contributions by males to females. Activity, especially flight, and oogenesis can compete for energy. Social insects exhibit extreme specializations in oogenesis. Food flow within colonies is a major factor regulating fecundity. Maternal nourishment is not needed for oogenesis in parasitoids and pseudoplacental viviparous insects. -from Author
• Wheeler, D. E., & Buck, N. A. (1996). A role for storage proteins in autogenous reproduction in Aedes atropalpus. Journal of Insect Physiology, 42(10), 961-966.
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  Abstract: In the autogenous mosquito, Aedes atropalpus, storage proteins accumulated during the larval stage may serve as an amino acid reserve for oogenesis, in addition to metamorphosis. Hexameric storage proteins accumulate during larval development and include subunits of three different masses: 62.5, 66, 72.5 kDa. All three types of subunits are found in the female but only the larger two are in males. In females, storage proteins are only partially depleted by the time of eclosion. The remaining protein amounts to about 40% of the original store. Males, in contrast, exhaust their supply of stored protein during metamorphosis. In the female, the storage proteins disappear over the first days after eclosion, and are depleted before vitellogenin/vitellin levels reach their maximum. This suggests that the amino acids held in storage proteins are transferred to vitellogenesis, enabling autogenous egg development. The fact that these amino acids are not available for egg development until after eclosion, later than in many other insects, probably reflects a relatively recent evolution from blood-feeding ancestors.
• Wheeler, D. E., & Buck, N. A. (1996). Depletion of reserves in ant queens during claustral colony founding. Insectes Sociaux, 43(3), 297-302.
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  Abstract: Gynes in the claustrally-founding species Crematogaster opuntiae and Camponotus festinatus accumulate large amounts of protein and lipid between the time of eclosion and mating. During colony founding, protein is depleted from both the thorax and abdomen and lipid from the abdomen. The abdomen, and specifically its accumulated storage protein, provides an amino acid store equivalent to or larger than that of flight muscle. The importance of this second major protein reserve in the evolution of claustral colony founding should be considered.
• Reichardt, A. K., & Wheeler, D. E. (1995). Estimation of sperm numbers in insects by fluorometry. Insectes Sociaux, 42(4), 449-452.
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  Abstract: To facilitate the study of mating biology in the desert leaf-cutter ant Acromyrmex versicolor, methods were developed that allowed storage and easy quantification of sperm samples collected from both male and female reproductive tracts. Sperm samples stored frozen were sonicated, stained with a fluorescent DNA stain, and the fluorescence emitted by the stained sperm heads was measured. The intensity of fluorescence was shown to be a linear function of the number of sperm in the sample as determined by counting. © 1995 Birkhäuser Verlag.
• Rosell, R. C., & Wheeler, D. E. (1995). Storage function and ultrastructure of the adult fat body in workers of the ant Camponotus festinatus (Buckley) (Hymenoptera : Formicidae). International Journal of Insect Morphology and Embryology, 24(4), 413-426.
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  Abstract: The presence of storage proteins in ants is perhaps most remarkable in its abundance in some species in the adult stage. The ultrastructure of fat body in workers of Camponotus festinatus (Hymenoptera : Formicidae) confirms that they do indeed store large quantities of protein, as well as lipid and carbohydrate, under some conditions. Rounded electron-dense granules, which are abundant in workers maintained in groups isolated from the parent colony, probably contain an arylphorin-like protein. Irregularly shaped electron-dense granules present in all workers regardless of age, caste or social environment, resemble primarily lysosomes, but lack acid phosphatase activity. Peroxisomes were also identified but were not associated with either type of dense granule. Lipid analysis showed that lipid storage followed similar patterns to protein storage, with isolated workers, especially soldiers, accumulating huge quantities of triglycerides. The relationship between storage of nutrient reserves and the presence of larvae suggests that the stores may function in regulating seasonal brood production. © 1995.
• Wheeler, D. E., & Buck, N. A. (1995). Storage proteins in ants during development and colony founding. Journal of Insect Physiology, 41(10), 885-894.
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  Abstract: Three classes of storage proteins from larvae of four species of ants (Crematogaster opuntiae, Pheidole spadonia, Solenopsis xyloni and Conomyrma sp.) were identified and characterized for native and subunit sizes, density and amino acid composition. First, hexamerins contained moderately high proportions of aromatic amino acids ( x ̄ = 12.9 mol%). A second type of storage protein contained extremely high proportions of glutamine/glutamic acid ( x ̄ = 21.1 mol%). Third, dimeric proteins had densities suggesting they were very high density lipoproteins (VHDL). These VHDLs may be homologous with similar proteins that carry chromophores in Lepidoptera. The same types of storage proteins found in larvae were also present in the fat bodies of adult queens at the time of their mating flights. The class of the dominant protein varied with species. In Cr. opuntiae queens, storage proteins were almost completely depleted during colony founding. In ants, the ability of adult females to express storage protein genes may have been an important step in the evolution of the claustral mode of colony initiation, in which females can produce the first set of workers without leaving the nest to search of food. © 1995.
• Wheeler, D. E., & Martinez, T. (1995). Storage proteins in ants (Hymenoptera:Formicidae). Comparative Biochemistry and Physiology -- Part B: Biochemistry and, 112(1), 15-19.
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  PMID: 7584843;Abstract: Storage proteins area major feature of holometabolous development in insects, accumulaüng during the larval period and disappearing during metamorphosis. In ants (Hymenoptera:Formicidae), storage proteins also play important roles in adult females. Three types of storage proteins have been characterized from ants: hexamerins, proteins high in glutamine/glutamic acid, and very high density lipoproteins (VHDLs). The hexamerins have moderately high levels of aromatic amino acids and belong to the arthropod hemocyanin family of proteins. The proteins high in glutamine/glutamic acid can form hexamers under some conditions, but the subunit size is larger than that of typical hexamerins. The VHDLs are dimeric and share features with storage chromoproteins described from Lepidoptera. In Camponotus festinatus (Formicinae), storage proteins are found in adult ants in two situations. First, lack of brood stimulates workers to accumulate the same two storage hexamers found in larvae. Second, young virgin queens store large reserves of these proteins before mating. Protein storage by queens has been confirmed in two other subfamilies of ants, indicating it is widespread. The capacity to store proteins as adults enables queens to rear brood without leaving the nest and workers to store rich reserves and regulate larval diet seasonally. © 1995.
• Martinez, T., & Wheeler, D. E. (1994). Storage proteins in adult ants (Camponotus festinatus): Roles in colony founding by queens and in larval rearing by workers. Journal of Insect Physiology, 40(8), 723-729.
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  Abstract: Camponotus festinatus storage hexamers (Hex 1 and 2), first identified in last instar larvae, constitute two major proteins in adult queens and broodless workers. We have examined the effects of colony founding by queens and larval rearing by workers on their storage protein content. Both hexamerins accumulate in virgin queens, particularly Hex 2 in the fat body where it makes up about 70% of total soluble proteins. Colony founding causes a depletion of Hex 1 and 2 in queens. Levels of these proteins begin to decrease by the end of the claustral period when the first workers emerge, and they are depleted from fat body and hemolymph 1 month later. Larval rearing has an inhibitory effect on the accumulation of storage proteins in workers. Hex 1 occurs only in low concentrations in the hemolymph of 2- and 4-week-old workers kept with larvae, and disappears thereafter. Hex 2 does not accumulate in 2- to 8-week-old workers kept with larvae. Our results with Camponotus queens support a role of the storage hexamers in egg development and/or nourishment of the brood. These data also suggest an important role of nutrition in the synthesis and accumulation of hexamerins in adult workers. © 1994.
• Wheeler, D. E., & Krutzsch, P. H. (1994). Ultrastructure of the spermatheca and its associated gland in the ant Crematogaster opuntiae (Hymenoptera, Formicidae). Zoomorphology, 114(4), 203-212.
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  Abstract: Sperm storage by females has reached an extreme degree of development in ants. Ant queens, which are unusually long-lived insects, typically store and maintain an unreplenished supply of viable sperm for ten or more years. The spermatheca of Crematogaster opuntiae includes a receptacle and a discrete pair of accessory, or spermathecal, glands, structures commonly found in sperm storage organs of insects. The bean-shaped receptacle consists of a layer of simple epithelium externally and a cuticular layer internally. In the hilar region, the epithelium is highly columnar and exhibits ultrastructural features characteristic of transport epithelia, such as infolded basal membranes, abundant polymorphic mitochondria, and apical microvilli. The spermathecal glands contain cells that have long, dense microvilli that project into a central lumen, abundant mitochondria, and large fields of glycogen. The valve and pump region of the spermatheca provide a mechanism to conserve sperm by controlling the rate of sperm release. The columnar epithelium may function as excretory tissue that serves to maintain an environment in which sperm can remain viable for many years. © 1994 Springer-Verlag.
• Martinez, T., & Wheeler, D. (1993). Identification of two storage hexamers in the ant, Camponotus festinatus: Accumulation in adult queenless workers. Insect Biochemistry and Molecular Biology, 23(2), 309-317.
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  PMID: 8485526;Abstract: Two electrophoretically and immunologically distinct storage hexamers (Hex 1 and Hex 2) have been identified in Camponotus festinatus workers. The molecular weights of the native molecules were estimated to be 460,000 (Hex 1) and 580,000 (Hex 2) by pore limiting gradient electrophoresis. Hex 1 partially dissociates with moderate alkaline pH. Both proteins are composed of a single type of apoprotein of approx. 73 (Hex 1) and 80 kDa (Hex 2). While most of Hex 2 is sequestered by the fat body before pupation, Hex 1 remains largely in the hemolymph during the last larval and pupal stages. Both proteins were detected only in low concentrations in the hemolymph of newly emerged adults, and they gradually disappear from adult workers maintained in the colonies. In queenless workers, however, Hex 1 and Hex 2 accumulate in the hemolymph and fat body, constituting the most abundant proteins together with vitellogenin. Camponotus festinatus storage hexamers bear some homologies in their N-terminal sequence with the arylphorins of Diptera and Lepitoptera, as well as with a crab hemocyanin. However, with respect to their amino acid composition, they can not be classified as arylphorins. © 1993.
• Wheeler, D. E., & Krutzsch, P. H. (1992). Internal reproductive system in adult males of the genus Camponotus (Hymenoptera: Formicidae: Formicinae).. Journal of Morphology, 211(3), 307-317.
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  PMID: 1635070;Abstract: Descriptions are provided of the histology and ultrastructure of the male internal reproductive tracts from three species of Camponotus, representing three subgenera. This study is the first to provide ultrastructural information on the testes (including spermatogenesis and spermiogenesis), seminal vesicles, and accessory glands in ants. Testes contain about ten follicles each, and each follicle is capable of producing hundreds of cysts in which spermatozoa develop. Structural evidence of meiosis in late pupal testes includes cytoplasmic bridges between spermatocytes, centriole elimination, and fusion of mitochondria. Developing spermatids are in close contact with cyst cells in the region of the acrosome. Mature spermatozoa are similar in ultrastructure to those described previously for two other subfamilies of ants (Myrmicinae and Dolichoderinae). The ultrastructure of the seminal vesicle suggests that it is not merely a passive organ for sperm storage. Large numbers of both mitochondria and membranous whorls suggest a pH-regulating and/or hormonal function. The accessory gland is made up of secretory cells that contain a diversity of secretory granules. SDS-PAGE reveals several proteins found in the accessory glands but absent in the adjacent genitalia. Preliminary analyses indicate that carbohydrate is an important component of accessory gland secretions.
• Martinez, T., & Wheeler, D. (1991). Effect of the queen, brood and worker caste on haemolymph vitellogenin titre in Camponotus festinatus workers. Journal of Insect Physiology, 37(5), 347-352.
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  Abstract: Haemolymph concentration of vitellogenin and ovary development have been examined in Camponotus festinatus workers under inhibited (queenright) and uninhibited (queenless) conditions, in order to determine which social factors may affect worker oögenesis. While most queeright workers had very low vitellogenin titres, queenless workers maintained either in the presence or absence of pupae showed increasing vitellogenin titres. Mean vitellogenin concentration in 7-week-old queenless soldiers and 10-week-old queenless minor workers were 15-fold higher than those found in queenright workers of the same age. Larvae had an inhibitory effect on the haemolymph vitellogenin titres of workers, particularly of minor workers. Soldiers in the presence of minor workers showed significantly higher vitellogenin titres during early adult life. In spite of the accumulation of vitellogenin in the haemolymph of queenless workers, even far above the levels detected in some queens, oöcyte development did not occur in the majority of these animals. © 1991.
• Martinez, T., & Wheeler, D. (1991). Identification of vitellogenin in the ant, Camponotus festinatus: changes in hemolymph proteins and fat body development in workers.. Archives of insect biochemistry and physiology, 17(2-3), 143-155.
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  PMID: 1802030;Abstract: Vitellogenin has been identified in the ant Camponotus festinatus, both in queens and workers. In the workers, it is already present before adult eclosion in low concentrations (less than 1 microgram/microliter hemolymph). Vitellogenin and vitellin are immunologically identical and are composed of a single type of apoprotein with an apparent Mr = 185,000. The molecular weight of the native molecules was estimated as approximately 460,000 by pore limiting gradient electrophoresis. Vitellogenin was detected as a major protein in the hemolymph of young workers, both under queenright and queenless conditions. Thus, in spite of their sterility in the presence of the queen, C. festinatus workers are able to synthetize vitellogenin which is identical both in size and immunologically to the queen vitellogenin. About 6-7 weeks after adult eclosion, however, vitellogenin was usually undetectable in the hemolymph of queenright workers, particularly the minor workers, while it constituted about 30% of total protein in queenless workers. Protein concentration in the hemolymph of queenless insects increased up to 20-fold as compared to 1-day-old insects. Queenless workers also developed large amounts of perivisceral fat body, while queenright workers, particularly the minor workers, showed a dramatic fat body regression about 6 weeks after emergence.
• Wheeler, D. E. (1991). The developmental basis of worker caste polymorphism in ants. American Naturalist, 138(5), 1218-1238.
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  Abstract: Diverse worker caste systems can be generated through regulation of three aspects of larval growth: critical size, growth parameters, and reprogramming of these factors. Even the most complex caste systems could have evolved simply by the addition of revised programs to the end of an ancestral developmental pathway for workers. Worker castes in ants provide a system in which to study the evolution of reaction norms and developmental switches. In ants, the simplest developmental switch, revision of critical size alone, does not lead to discontinuous phenotypes. Only when changes in growth rules are tied to the decision to revise critical size are distinct phenotypes produced from the alternative developmental programs. -from Author
• Wheeler, D. E. (1990). The developmental basis of worker polymorphism in fire ants. Journal of Insect Physiology, 36(5), 315-322.
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  Abstract: The fire ant, Solenopsis invicta, has a relatively simple worker caste. Workers show a wide size range but maintain near proportionality over that range. Data on normal and hormonally manipulated growth suggest a developmental mechanism underlying the production of two populations of workers that together form a single, highly skewed size-frequency distribution. The mechanism involves regulation of two sets of critical sizes for metamorphosis. Larvae that reached a large size during the 3rd instar relative to their cohort became major workers. Major workers were much larger than could be predicted by the relationship between larval and pupal sizes of minor workers. Methoprene treatment increased the mean size of workers. The mechanism of these increases differs with timing of application. Treatment during early instars increased size at the moult to the last instar, and this increase was translated into a large pupal size. Treatment during the 4th instar caused a metamorphic delay during which larvae continued to grow. Although worker size can be manipulated with methoprene, it is not clear if juvenile hormone plays any role in resetting critical size. The type of control of size-frequency distributions found in S. invicta may apply to other ant species. © 1990.
• Wheeler, D. E., & Kawooya, J. K. (1990). Purification and characterization of honey bee vitellogenin.. Archives of insect biochemistry and physiology, 14(4), 253-267.
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  PMID: 2134180;Abstract: A protocol has been developed for the purification of vitellogenin from the honey bee, Apis mellifera. Purification allows for the first characterization of a vitellogenin from the large order Hymenoptera. Hymenopteran vitellogenins are unusual among insect vitellogenins in that they contain only one type of apoprotein. The honey bee vitellogenin was isolated from hemolymph of honey bee queens by a combination of density gradient ultracentrifugation, ion-exchange chromatography, and affinity chromatography. The native vitellogenin particle is a very high density glycolipoprotein containing approximately 91% protein, 7% lipid, and 2% carbohydrate. Phospholipid and diacylglycerol are the major lipid components. The equilibrium density (1.28 g/ml) is the same as that for Manduca sexta vitellogenin, which contains a much higher proportion of lipid. The covalently bound carbohydrate moiety of the particle is high in mannose. The amino acid composition of vitellogenin is similar to those of vitellogenins from other insect species. The N-terminal amino acid sequence of the apoprotein was determined, the first such sequence for any insect vitellogenin. When analyzed by sodium dodecyl sulfate (SDS)-gel electrophoresis, A. mellifera vitellogenin resolved into a single band with an apparent Mr of 180,000. Gel filtration under reducing and native conditions yielded estimated Mr values of about 300,000.
• Wheeler, D. E., Crichton, E. G., & Krutzsch, P. H. (1990). Comparative ultrastructure of ant spermatozoa (Formicidae: Hymenoptera). Journal of Morphology, 206(3), 343-350.
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  PMID: 2280410;
• Wheeler, D. E. (1986). Developmental and physiological determinants of caste in social Hymenoptera: evolutionary implications.. American Naturalist, 128(1), 13-34.
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  Abstract: The eusociality threshold, marked by cooperative brood care by mother and daughters, is crossed by both halictine bees and polistine wasps. Beyond the eusociality threshold lies the continued evolution and elaboration of social systems. Two particularly important thresholds of advanced colony organization are marked by morphological commitment to caste: 1) a commitment to queen-worker dimorphism, and 2) a commitment to morphological diversity within the worker form. Queen-worker dimorphism is a defining character of highly eusocial caste systems. If morphological differences exist between queens and workers, the pattern of queen and worker development must diverge no later than the larval stage. Larvae must be able to translate their own developmental, especially nutritional, history into a development decision. The linking and coordinate expression of gyne characters are advantageous when intermediates are less fit than full queens or full workers. Once such a developmental system evolves, individuals become extremely vulnerable to control by other colony members that have an interest in their developmental fate. In highly eusocial Hymenoptera, queens use 2 principal mechanisms to control offspring development: direct control of nutrition (eg honeybees Apis) and interference with larval response to nutrition (eg Bombus terrestris, many ants). A 2nd major threshold in the evolution of morphologically complex caste systems is the addition of multiple physical worker castes. -from Author
• Wheeler, D. E., & Nijhout, H. F. (1984). Soldier determination in Pheidole bicarinata: Inhibition by adult soldiers. Journal of Insect Physiology, 30(2), 127-135.
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  Abstract: In the ant Pheidole bicarinata, adult soldiers suppress the induction of soldier developments in larvae that have been treated with methoprene, as well as in acetone-treated controls. Induction of soldier development is inhibited in methoprene-treated larvae when the adult soldiers are present as nurses, when they are present in the colony but minor workers serve as nurses, and when they are held in a minor worker-permeable cage to prevent them from contacting larvae. Suppression of soldier determination can be overridden by high doses of methoprene applied during the juvenile hormone-sensitive period for soldier determination. The degree of suppression increases with increasing contact between larvae and adult soldiers. The most likely mechanism of inhibition is a contact soldier pheromone. On the basis of our results, we expand our model of soldier determination to accommodate the fact that the threshold titre of juvenile hormone necessary to induce soldier development changes in the presence of soldiers. A threshold that is sensitive to the presence of adult soldiers provides a mechanism whereby the worker caste ratio in colonies can be regulated. © 1984.
• Wheeler, D. E., & Nijhout, H. F. (1983). Soldier determination in Pheidole bicarinata: Effect of methoprene on caste and size within castes. Journal of Insect Physiology, 29(11), 847-854.
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  Abstract: Topical application of methoprene to final-instar larvae of the ant Pheidole bicarinata can induce soldier development. Soldier induction takes place if methoprene levels are above a soldier-determining threshold during a critical period of juvenile hormone-sensitivity that occurs during about days 4-6 of the final instar. Furthermore, the amount of exogenous methoprene applied affects the timing of metamorphosis and the adult size in both the minor worker and soldier castes. When larvae that receive methoprene treatment become minor workers these are always larger than acetone-treated controls. In larvae that become soldiers, growth and timing of metamorphosis vary with the dose of methoprene, but in a more complex way. A high dose of methoprene produces a metamorphic delay and large soldiers. However, the lowest effective dose for soldier induction produces early metamorphosis and small adults. On the basis of these results, we have expanded our model of a mechanism by which juvenile hormone could control determination of worker castes in Pheidole bicarinata. © 1983.
• Nijhout, H. F., & Wheeler, D. E. (1982). Juvenile hormone and the physiological basis of insect polymorphisms.. Quarterly Review of Biology, 57(2), 109-133.
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  Abstract: Juvenile hormone is involved in the control of gene switching and exerts this control only during certain critical periods. As a rule one or more critical periods exist during each pre-reproductive instar. The presence or absence of JH during any given critical period somehow causes the insect to 'choose' between alternative developmental pathways. Using this model for the action of JH, the authors discuss the endocrine control of metamorphosis, phase determination in locusts and aphids, caste determination in social insects, and certain color polymorphisms. -from Authors
• Wheeler, D. E., & Nijhout, H. F. (1981). Imaginal wing discs in larvae of the soldier caste of Pheidole bicarinata vinelandica Forel (Hymenoptera : Formicidae). International Journal of Insect Morphology and Embryology, 10(2), 131-139.
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  Abstract: In Pheidole bicarinata vinelandica, soldier larvae have prominent mesothoracic wing discs. Imaginal wing discs are suppressed in minor worker larvae. In soldiers, wing discs appear abruptly late in larvae life and are unusually large when compared with wing discs in worker larvae of other ant genera. Once development has been initiated, wing discs of soldier larvae grow at a rate comparable to soldier leg discs. The dynamics of development of soldier wing discs differ fundamentally from those of other holometabolous insects, worker ants and Pheidole bicarinata queens. This unusual developmental pattern may provide a clue to the physiological basis and timing of soldier determination. © 1981 Pergamon Press Ltd.
• Wheeler, D. E., & Nijhout, H. F. (1981). Soldier determination in ants: New role for juvenile hormone. Science, 213(4505), 361-363.
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  PMID: 17819911;

Poster Presentations

• Rodrigues, P. (2014, July). Are ants like cows? Compartmentalization of gut bacteria in an herbivore insect.. International Congress of the IUSSI.. Cairns, Australia: Internation Union for the Study of Social Insects.
• Rodrigues, P. (2014, July). Morphological adaptation for gut partitioning in the ant Cephalotes rowheri.. International Congress of the Study of Social Insects. Cairns, Australia: Internation Union for the Study of Social Insects.
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  Herbivores such as cows and rabbits evolved specialized portions of their gut where symbiotic microorganisms are found. Cephalotes, believed to herbivorous, also have such a pouch containing numerous bacteria.Using next gen sequencing, we found clear compartmentalization.
• Rodrigues, P. A. (2014, April). Rodrigues, P., M. Lanan, D. Wheeler. P. Lukasik, J. Russell, and D. Wheeler. Are ants like cows? Compartmentalization of gut bacteria in an herbivore insect.. 98th Pacific Branch Meeting of the Entomological Society of America Rodrigues, P., M. Lanan, D. Wheeler. P. Lukasik, J. Russell, and D. Wheeler. Are ants like cows? Compartmentalization of gut bacteria in an herbivore insect. 98th Pacific Branch Meeting of t.