Margaret E Evans
- Associate Professor, Dendrochronology
- Member of the Graduate Faculty
- Associate Professor, Arid Lands Resources Sciences - GIDP
- Associate Professor, Natural Resources
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Conservation BiologyECOL 406R (Spring 2023)
Conservation BiologyECOL 506R (Spring 2023)
Conservation BiologyRNR 506R (Spring 2023)
Forest EcologyECOL 433 (Fall 2022)
Forest EcologyECOL 533 (Fall 2022)
Forest EcologyGEOS 533 (Fall 2022)
Forest EcologyRNR 433 (Fall 2022)
Forest EcologyRNR 533 (Fall 2022)
Natural Resources SeminarRNR 596B (Fall 2021)
Natural Resources SeminrRNR 496B (Fall 2021)
Conservation BiologyECOL 406R (Spring 2021)
Conservation BiologyECOL 506R (Spring 2021)
PreceptorECOL 391 (Spring 2021)
ThesisECOL 910 (Spring 2021)
ResearchECOL 900 (Fall 2020)
Biology Lecture TutorECOL 497B (Spring 2020)
Conservation BiologyECOL 406R (Spring 2020)
Conservation BiologyECOL 506R (Spring 2020)
ThesisECOL 910 (Spring 2020)
ResearchECOL 900 (Fall 2019)
Tpcs in DendrochronologyGEOS 595E (Fall 2019)
Conservation BiologyECOL 406R (Spring 2019)
Conservation BiologyRNR 506R (Spring 2019)
ResearchECOL 900 (Spring 2019)
Tpcs in DendrochronologyGEOS 595E (Spring 2019)
Undgrad Tching Trng EcolECOL 497A (Spring 2019)
ResearchECOL 900 (Fall 2018)
Conservation BiologyECOL 406R (Spring 2018)
Conservation BiologyECOL 506R (Spring 2018)
Independent StudyECOL 499 (Spring 2018)
Intrnship Present+PlanECOL 610C (Spring 2018)
Rsrch Ecology+EvolutionECOL 610A (Spring 2018)
Undgrad Tching Trng EcolECOL 497A (Spring 2018)
Intrnship Present+PlanECOL 610C (Fall 2017)
Conservation BiologyECOL 406R (Spring 2017)
Conservation BiologyRNR 506R (Spring 2017)
Intrnship Present+PlanECOL 610C (Spring 2017)
Undgrad Tching Trng EcolECOL 497A (Spring 2017)
Intrnship Present+PlanECOL 610C (Fall 2016)
Rsrch Ecology+EvolutionECOL 610A (Fall 2016)
Conservation BiologyECOL 406R (Spring 2016)
Conservation BiologyECOL 506R (Spring 2016)
Conservation BiologyRNR 506R (Spring 2016)
Rsrch Ecology+EvolutionECOL 610A (Spring 2016)
Undgrad Tching Trng EcolECOL 497A (Spring 2016)
- Evans, M. E., Black, B. A., Falk, D. A., Giebink, C. L., & Schultz, E. L. (2022). Growth Rings across the Tree of Life: demographic insights from biogenic time series data.. In Demographic Methods Across the Tree of Life.. Oxford University Press.
- Dennhart, A. J., Evans, M. E., Dechner, A., Hunt, L. E., & Maurer, B. A. (2016). Macroecology and the Theory of Island Biogeography: Abundant Utility for Applications in Restoration Ecology. In Foundations of Restoration Ecology, Second Edition.
- Soulebeau, A., Pellens, R., Lowry, P. P., Aubriot, X., Evans, M. E., & Haevermans, T. (2016). Conservation of Phylogenetic Diversity in Madagascar's largest endemic plant family, Sarcolaenaceae. In Biodiversity Conservation and Phylogenetic Systematics(pp 355-374). Springer. doi:10.1007/978-3-319-22461-9_18
- Heilman, K. A., Dietze, M. C., Arizpe, A., Aragon, J., Grey, A., Shaw, J. D., Finley, A. O., Klesse, S., DeRose, R. J., & Evans, M. E. (2022). Ecological forecasting of tree growth: regional fusion of tree-ring and forest inventory data to quantify drivers and characterize uncertainty. Global Change Biology, 28, 2442-2460. doi:https://onlinelibrary.wiley.com/doi/10.1111/gcb.16038
- Schultz, E., Huelsmann, L., Pillet, M. D., Hartig, F., Breshears, D. D., Record, S., Shaw, J. D., DeRose, R. J., Zuidema, P., & Evans, M. E. (2022). Climate-driven, but dynamic and complex? A reconciliation of competing hypotheses for species’ distributions. Ecology Letters, 25, 38-51. doi:https://onlinelibrary.wiley.com/doi/10.1111/ele.13902
- DeRose, R. J., Evans, M. E., Klesse, S., Alexander, M. R., Babst, F., Bouchard, M., Cahoon, S. M., Canham, C. D., Frank, D. C., Girardin, M. P., Gomez, A., Gutierrez-Garcia, G., Villela-Gaytan, S. A., Olds, C., Rayback, S. A., Reid, A., Ricker, M., Schaberg, P. G., Shaw, J. D., & Sullivan, P. F. (2022). The case for adding tree rings to North America’s national forest inventories: an essential tool to guide drawdown of atmospheric CO2. BioScience. doi:https://academic.oup.com/bioscience/advance-article/doi/10.1093/biosci/biab119/6449092
- Klesse, S., DeRose, R. J., Shaw, J. D., Babst, F., Anderegg, L., Axelson, J., Black, B., Ettinger, A., Greisbauer, H., Guiterman, C., Harley, G., Harvey, J., Lo, Y., Lynch, A., O'Connor, C., Restaino, C., Sauchyn, D., Smith, D., Wood, L., , Villanueva, J., et al. (2020). Continental-scale tree ring-based projection of Douglas-fir growth - testing the limits of space-for-time substitution. Global Change Biology, 26, 5146-5163.
- Ricker, M., Gutierrez-Garcia, G., Juarez-Guerrero, D., & Evans, M. E. (2020). Statistical age determination of tree rings. PLoS One, 15(9), e0239052. doi:https://doi.org/10.1371/journal.pone.0239052
- Babst, F., Evans, M. E., Zhang, Z., Bodesheim, P., Turton, R., Charney, N., Friend, A., Trouet, V. M., Record, S., Girardin, M., Poulter, B., Klesse, S., Mahecha, M., Moore, D. J., Seftigen, K., Frank, D. C., Bjorklund, J., Enquist, B. J., Eckes, A., , Bouriaud, O., et al. (2018). When tree rings go global: challenges and opportunities for retro- and prospective insight. Quarternary Science Reviews, 197, 1-20. doi:https://doi.org/10.1016/j.quascirev.2018.07.009
- Evans, M. E., Gugger, P. F., Lynch, A. M., Guiterman, C. H., Fowler, J. C., Klesse, S., & Riordan, E. C. (2018). Dendroecology meets genomics in the common garden: new insights on climate adaptation (invited Commentary). New Phytologist, 218, 401-403.
- Klesse, S., DeRose, R. J., Guiterman, C. H., Lynch, A. M., O'Connor, C. D., Shaw, J. D., & Evans, M. E. (2018). Sampling bias overestimates climate change impacts on forest growth in the Southwestern United States. Nature Communications, 9, 5336. doi:doi.org/10.1038/s41467-018-07800-y
- Wolf, B., Wen, J., Mcginty, M., Hearn, D. J., & Evans, M. E. (2018). Dispersal is associated with morphological innovation, but not increased diversification, in Cyphostemma (Vitaceae). Journal of Systematics and Evolution, 56(4), 340-359. doi:10.1111/jse.12417
- Evans, M. E., Falk, D. A., Arizpe, A., Swetnam, T., Babst, F., & Holsinger, K. E. (2017). Fusing tree-ring and forest inventory data to infer influences on tree growth. EcoSphere, e01889. doi:10.1002/ecs2.1889
- Pillet, M., Joetzjer, E., Belmin, C., Chave, J., Ciais, P., Dourdain, A., Evans, M. E., Herault, B., Luyssaert, S., & Poulter, B. (2017). Disentangling competitive vs. climatic effects on tropical forest mortality. Journal of Ecology. doi:10.1111/1365-2745.12876
- Vanderwel, M., Rozendaal, D., & Evans, M. E. (2017). Predicting the abundance of forest types across the eastern U.S. through inverse modelling of tree-level demography. Ecological Applications, 27, 2128-2141. doi:10.1002/eap.1596
- Charney, N., Babst, F., Poulter, B., Record, S., Trouet, V. M., Frank, D. C., Enquist, B. J., & Evans, M. E. (2016). Observed forest sensitivity to climate implies larger reductions in 21st century forest growth. Ecology Letters.
- Evans, M. E., Merow, C., Record, S., McMahon, S., & Enquist, B. J. (2016). Making process-based range forecasts for many species. Trends in Ecology and Evolution, 31(11), 860-871. doi:http://dx.doi.org/10.1016/j.tree.2016.08.005
- Hearn, D. J., Evans, M. E., Wolf, B., McGinty, M., & Wen, J. (2017). Dispersal is associated with morphological innovation, but not increased diversification, in Cyphostemma (Vitaceae). Journal of Systematics and Evolution, 56(4), 340-359. doi:doi: 10.1111/jse.12417
- Evans, M. E., Aubriot, X., Hearn, D., Lanciaux, M., Lavergne, S., Cruaud, C., Lowry, P. P., & Haevermans, T. (2014). Insights on the Evolution of Plant Succulence from a Remarkable Radiation in Madagascar (Euphorbia). Systematic Biology, 63(5), 698-711.
- Merow, C., Dahlgren, J. P., Metcalf, C. J., Childs, D. Z., Evans, M. E., Jongejans, E., Record, S., Rees, M., Salguero-Gomez, R., & McMahon, S. M. (2014). Advancing population ecology with integral projection models: a practical guide. Methods in Ecology and Evolution, 99-110.
- Merow, C., Dalgren, J. P., Metcalf, C. J., Metcalf, C. J., Childs, D. Z., Evans, M. E., Jongejans, E., Record, S., Rees, M., Salguero-gomez, R., & Mcmahon, S. M. (2013). Data from: Advancing population ecology with integral projection models: a practical guide. Methods in Ecology and Evolution. doi:10.5061/DRYAD.6575F
- Thuiller, W., Lavergne, S., Jiguet, F., Evans, M. E., & Burfield, I. J. (2013). Are species' responses to global change predicted by past niche evolution?. Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 368(1610), 20120091. doi:10.1098/rstb.2012.0091More infoPredicting how and when adaptive evolution might rescue species from global change, and integrating this process into tools of biodiversity forecasting, has now become an urgent task. Here, we explored whether recent population trends of species can be explained by their past rate of niche evolution, which can be inferred from increasingly available phylogenetic and niche data. We examined the assemblage of 409 European bird species for which estimates of demographic trends between 1970 and 2000 are available, along with a species-level phylogeny and data on climatic, habitat and trophic niches. We found that species' proneness to demographic decline is associated with slow evolution of the habitat niche in the past, in addition to certain current-day life-history and ecological traits. A similar result was found at a higher taxonomic level, where families prone to decline have had a history of slower evolution of climatic and habitat niches. Our results support the view that niche conservatism can prevent some species from coping with environmental change. Thus, linking patterns of past niche evolution and contemporary species dynamics for large species samples may provide insights into how niche evolution may rescue certain lineages in the face of global change.
- Holsinger, K. E., & Evans, M. E. (2012). Estimating covariation between vital rates: a simulation study of connected vs. separate generalized linear mixed models (GLMMs).. Theoretical population biology, 82(4), 299-306. doi:10.1016/j.tpb.2012.02.003More infoCovariation between vital rates is recognized as an important pattern to be accounted for in demographic modeling. We recently introduced a model for estimating vital rates and their covariation as a function of known and unknown effects, using generalized linear mixed models (GLMM's) implemented in a hierarchical Bayesian framework (Evans et al., 2010) In particular, this model included a model-wide year effect (YEAR) influencing all vital rates, which we used to estimate covariation between vital rates due to exogenous factors not directly included in the model. This YEAR effect connected the GLMMs of vital rates into one large model; we refer to this as the "connected GLMMs" approach. Here we used a simulation study to evaluate the performance of a simplified version of this model, compared to separate GLMMs of vital rates, in terms of their ability to estimate correlations between vital rates. We simulated data from known relationships between vital rates and a covariate, inducing correlations among the vital rates. We then estimated those correlations from the simulated data using connected vs. separate GLMMs with year random effects. We compared precision and accuracy of estimated vital rates and their correlations under three scenarios of the pervasiveness of the exogenous effect (and thus true correlations). The two approaches provide equally good point estimates of vital rate parameters, but connected GLMMs provide better estimates of covariation between vital rates than separate GLMMs, both in terms of accuracy and precision, when the common influence on vital rates is pervasive. We discuss the situations where connected GLMMs might be best used, as well as further areas of investigation for this approach.
- Theiss, K. E., Holsinger, K. E., Hearn, D. J., Evans, M. E., Donoghue, M. J., & Cranston, K. (2011). Extreme environments select for reproductive assurance: evidence from evening primroses (Oenothera).. The New Phytologist, 191(2), 555-563. doi:10.1111/j.1469-8137.2011.03697.xMore infoCompeting evolutionary forces shape plant breeding systems (e.g. inbreeding depression, reproductive assurance). Which of these forces prevails in a given population or species is predicted to depend upon such factors as life history, ecological conditions, and geographical context. Here, we examined two such predictions: that self-compatibility should be associated with the annual life history or extreme climatic conditions. We analyzed data from a clade of plants remarkable for variation in breeding system, life history and climatic conditions (Oenothera, sections Anogra and Kleinia, Onagraceae). We used a phylogenetic comparative approach and Bayesian or hybrid Bayesian tests to account for phylogenetic uncertainty. Geographic information system (GIS)-based climate data and ecological niche modeling allowed us to quantify climatic conditions. Breeding system and reproductive life span are not correlated in Anogra and Kleinia. Instead, self-compatibility is associated with the extremes of temperature in the coldest part of the year and precipitation in the driest part of the year. In the 60 yr since this pattern was anticipated, this is the first demonstration of a relationship between the evolution of self-compatibility and climatic extremes. We discuss possible explanations for this pattern and possible implications with respect to anthropogenic climate change.
- Menges, E. S., Holsinger, K. E., & Evans, M. E. (2010). Fire, vital rates, and population viability: a hierarchical Bayesian analysis of the endangered Florida scrub mint. Ecological Monographs, 80(4), 627-649. doi:10.1890/09-1758.1More infoUnderstanding and predicting changes in the abundance of natural populations is a central goal of ecology. These changes are influenced by a variety of exogenous processes (weather, floods, fire); variation in these processes leads to variation in vital rates (survival, fecundity) that may be positively or negatively correlated across the life cycle. We used 20 years of data and a hierarchical Bayesian model to estimate vital rates and their covariation in an endangered plant, Dicerandra frutescens ssp. frutescens (Lamiaceae), as a function of time since fire and random year effects. Germination and the number of flowering branches declined with time since fire, and all plants were increasingly likely to become nonreproductive with time since fire. Time since fire had negative effects on survival of seedlings, vegetative plants, and small flowering plants, and positive effects on survival of medium and large flowering plants. Model comparison strongly supported inclusion of time-since-fire effects and weakly supported inclusion of year effects influencing all vital rates (''model-wide'' year effects). We used samples from the joint posterior distribution of model parameters to simulate population dynamics as a function of fire regime and year-to-year environmental variation. These simulations suggest that populations of Dicerandra frutescens ssp. frutescens are least likely to go extinct if the average time between fires is ;24-30 years. The design of the simulations allowed us to distinguish variation in stochastic population growth associated with process variability (fire, year effects, and demographic stochasticity) from variation associated with parameter uncertainty (finite amounts of data). Even with 20 years of data, half or more of the uncertainty in population growth rates was due to parameter uncertainty. This hierarchical Bayesian population viability analysis illustrates a general analytical framework for (1) estimating vital rates as a function of an exogenous environmental factor, (2) accounting for covariation among vital rates, and (3) simulating population dynamics as a function of stochastic environmental processes while taking into account uncertainty about their effects. We discuss future areas of development for this approach.
- Theiss, K. E., Holsinger, K. E., & Evans, M. E. (2010). Breeding system variation in 10 evening primroses (Oenothera sections Anogra and Kleinia; Onagraceae).. American journal of botany, 97(6), 1031-9. doi:10.3732/ajb.0900260More infoWe examined two accounts of the relationship between breeding system and life history variation in a clade of evening primroses (Oenothera, Onagraceae): (1) selection for reproductive assurance should generate an association between self-compatibility and monocarpy and (2) phylogenetic conservatism leads to retention of breeding system and life history traits among closely related taxa. •.We performed over 4000 hand pollinations under greenhouse conditions to determine the compatibility of 10 Oenothera taxa (sections Anogra [17 taxa] and Kleinia [2 taxa)] for which breeding systems had not previously been reported. We used generalized linear mixed models to evaluate the influence of pollination treatment, parents, and population on fruiting success. •.Among the taxa tested, six were self-incompatible, two were variable in compatibility, and two were self-compatible. We combined these data with published studies in Anogra and Kleinia and mapped breeding system and life history onto a published phylogeny. •.We found no evidence for phylogenetic conservatism, but detected considerable evolutionary lability in both traits. Additionally, we found no evidence for a consistent relationship between breeding system and life history. Only eight of 19 taxa followed the predicted association between self-incompatibility and polycarpy vs. self-compatibility and monocarpy. Instead, many taxa have retained self-incompatibility, regardless of monocarpy or polycarpy.
- Smith, S. A., Flynn, R. S., Evans, M. E., & Donoghue, M. J. (2009). Climate, niche evolution, and diversification of the "bird-cage" evening primroses (Oenothera, sections Anogra and Kleinia).. The American naturalist, 173(2), 225-40. doi:10.1086/595757More infoWe integrate climatic niche models and dated phylogenies to characterize the evolution of climatic niches in Oenothera sections Anogra and Kleinia (Onagraceae), and from that we make inferences on diversification in relation to climate. The evolution of climatic tolerances in Anogra + Kleinia has been heterogeneous, across phylogenetic groups and across different dimensions of climate. All the extant taxa occur in semiarid to arid conditions (annual precipitation of 10.1-49.1 cm and high temperatures in the warmest month of 28.5 degrees-40.1 degrees C), but there is striking variation among taxa in their climatic tolerances, especially temperature (minimum temperatures in the coldest month of -14.0 degrees to 5.3 degrees C) and summer versus winter precipitation (precipitation in the warmest quarter of 0.6-19.4 cm). Climatic disparity is especially pronounced in two subclades (californica, deltoides) that radiated in the southwestern United States and California, apparently including both divergent and convergent evolution of climatic tolerances. This niche evolution is remarkable, given the probable timescale of the radiation (approximately 1 million years). We suggest that the spatiotemporal climatic heterogeneity of western North America has served as a driver of diversification. Our data are also consistent with Axelrod's hypothesis that the spread of arid conditions in western North America stimulated diversification of arid-adapted lineages.
- Tully, T., Gallet, R., & Evans, M. E. (2009). Ecological conditions affect evolutionary trajectory in a predator-prey system.. Evolution; international journal of organic evolution, 63(3), 641-51. doi:10.1111/j.1558-5646.2008.00559.xMore infoThe arms race of adaptation and counter adaptation in predator-prey interactions is a fascinating evolutionary dynamic with many consequences, including local adaptation and the promotion or maintenance of diversity. Although such antagonistic coevolution is suspected to be widespread in nature, experimental documentation of the process remains scant, and we have little understanding of the impact of ecological conditions. Here, we present evidence of predator-prey coevolution in a long-term experiment involving the predatory bacterium Bdellovibrio bacteriovorus and the prey Pseudomonas fluorescens, which has three morphs (SM, FS, and WS). Depending on experimentally applied disturbance regimes, the predator-prey system followed two distinct evolutionary trajectories, where the prey evolved to be either super-resistant to predation (SM morph) without counter-adaptation by the predator, or moderately resistant (FS morph), specialized to and coevolving with the predator. Although predation-resistant FS morphs suffer a cost of resistance, the evolution of extreme resistance to predation by the SM morph was apparently unconstrained by other traits (carrying capacity, growth rate). Thus we demonstrate empirically that ecological conditions can shape the evolutionary trajectory of a predator-prey system.
- Menges, E. S., Holsinger, K. E., & Evans, M. E. (2008). Modeling the effect of fire on the demography of Dicerandra frutescens ssp. frutescens (Lamiaceae), an endangered plant endemic to Florida scrub. Population Ecology, 50(1), 53-62. doi:10.1007/s10144-007-0060-6More infoManaging populations, either for conservation, harvesting, or control, requires a mechanistic or semi-mechanistic understanding of population dynamics. Here, we investigate how time-since-fire affects demographic transitions in an endangered plant, Dicerandra frutescens ssp. frutescens (Lamiaceae), which is specialized to gaps created by fire. We used a hierarchical Bayesian model to estimate transition probabilities (i.e., the elements of population projection matrices) as a function of time-since-fire and random effects, from 13 years of data on marked individuals in five populations. Using a standard Bayesian criterion to compare models, we find that death becomes increasingly probable and progression increasingly improbable with time-since-fire. The magnitude of some of the time-since-fire effects is substantial: death is 3–5 times more likely for flowering plants >6 years versus 3–6 years post-fire, 3-step progression is almost 7 times less likely, and large flowering plants are more than 6 times more likely to stop flowering. These insights inspire new hypotheses about the underlying cause of decline with time-since-fire, and how it can be managed. Our approach can be used by others who wish to model the effect of an exogenous factor on demography, while rigorously accounting for uncertainty and variability.
- Ferriere, R., Venable, D. L., Kane, M. J., Ferriere, R., & Evans, M. E. (2007). Bet hedging via seed banking in desert evening primroses (Oenothera, Onagraceae): demographic evidence from natural populations.. The American naturalist, 169(2), 184-94. doi:10.1086/510599More infoBet hedging is one solution to the problem of an unpredictably variable environment: fitness in the average environment is sacrificed in favor of lower variation in fitness if this leads to higher long-run stochastic mean fitness. While bet hedging is an important concept in evolutionary ecology, empirical evidence that it occurs is scant. Here we evaluate whether bet hedging occurs via seed banking in natural populations of two species of desert evening primroses (Oenothera, Onagraceae), one annual and one perennial. Four years of data on plants and 3 years of data on seeds yielded two transitions for the entire life cycle. One year was exceptionally dry, leading to reproductive failure in the sample areas, and the other was above average in precipitation, leading to reproductive success in four of five populations. Stochastic simulations of population growth revealed patterns indicative of bet hedging via seed banking, particularly in the annual populations: variance in fitness and fitness in the average environment were lower with seed banking than without, whereas long-run stochastic mean fitness was higher with seed banking than without across a wide range of probabilities of the wet year. This represents a novel, unusually rigorous demonstration of bet hedging from field data.
- Evans, M. E., & Dennehy, J. J. (2005). Germ banking: bet-hedging and variable release from egg and seed dormancy.. The Quarterly review of biology, 80(4), 431-51. doi:10.1086/498282More infoMany species produce eggs or seeds that refrain from hatching despite developmental preparedness and favorable environmental conditions. Instead, these propagules hatch in intervals over long periods. Such variable hatch or germination tactics may represent bet-hedging against future catastrophes. Empiricists have independently recognized these approaches in diverse species. Terms such as seed banking, delayed egg hatching, and embryonic diapause have been used to describe these tactics, but connections between fields of study have been rare. Here we suggest a general term, germ banking, to incorporate all previous terms, unifying many seemingly disparate biological strategies under a single definition. We define the phenomenon of germ banking and use several biological examples to illustrate it. We then discuss the different causes of variation in emergence timing, delineate which constitute germ banking, and distinguish between germ banking and optimal timing of diapause. The wide-ranging consequences of germ banking are discussed, including modification of the age structure of a population, the alteration of microevolutionary dynamics, the migration of alleles from the past, the maintenance of genetic and species diversity, and the promotion of species coexistence. We end by posing questions to direct future research.
- Venable, D. L., Spangle, J. M., Hearn, D. J., Hahn, W. J., & Evans, M. E. (2005). Climate and life-history evolution in evening primroses (Oenothera, Onagraceae) : A phylogenetic comparative analysis. Evolution, 59(9), 1914-1927. doi:10.1111/j.0014-3820.2005.tb01061.xMore infoEvolutionary ecologists have long sought to understand the conditions under which perennial (iteroparous) versus annual (semelparous) plant life histories are favored. We evaluated the idea that aridity and variation in the length of droughts should favor the evolution of an annual life history, both by decreasing adult survival and by increasing the potential for high seedling survival via reduced plant cover. We calculated phylogenetically independent contrasts of climate with respect to life history in a clade of winter-establishing evening primroses (sections Anogra and Kleinia; Oenothera; Onagraceae), which includes seven annuals, 12 perennials, and two variable taxa. Climate variables were quantified from long-term records at weather stations near collection localities. To explicitly account for phylogenetic uncertainty, contrasts were calculated on a random sample of phylogenetic trees from the posterior distribution of a Bayesian analysis of DNA sequence data. Statements of association are based on comparing the per- tree mean contrast, which has a null expectation of zero, to a set of per-tree mean contrasts calculated on the same trees, after randomizing the climate data. As predicted, increased annual aridity, increased annual potential evapo- transpiration, and decreased annual precipitation were associated with transitions to the annual habit, but these trends were not significantly different from the null pattern. Transitions to the annual habit were not significantly associated with increases in one measure of aridity in summer nor with increased summer drought, but they were associated with significantly increased maximum summer temperatures. In winter, increased aridity and decreased precipitation were significantly associated with transitions to the annual habit. Changes in life history were not significantly associated with changes in the coefficient of variation of precipitation, either on an annual or seasonal (summer vs. winter) basis. Though we cannot attribute causality on the basis of a correlational, historical study, our results are consistent with the idea that increased heat and drought at certain times of the year favor the evolution of the annual habit. Increased heat in summer may cause adult survival to decline, while increased aridity and decreased precipitation in the season of seedling recruitment (winter) may favor a drought-avoiding, short-lived annual strategy. Not all of the predicted patterns were observed: the capability for drought-induced dormancy may preclude change in habit in response to summer drought in our study group.
- Menges, E. S., Gordon, D. R., & Evans, M. E. (2004). Mating systems and limits to seed production in two Dicerandra mints endemic to Florida scrub. Biodiversity and Conservation, 13(10), 1819-1832. doi:10.1023/b:bioc.0000035869.12388.0fMore infoWe used hand-pollination experiments to test the mating systems of and evaluate limits to seed production in two federally listed endangered plants endemic to the Lake Wales Ridge in Florida, USA: Dicerandra frutescens Shinners ssp. frutescens Huck and D. christmanii Huck and Judd (Lamiaceae). Both are nonclonal, short-lived perennials found in gaps created by disturbance (e.g., fire, roads) in Florida scrub. We found that both species require pollen and insect visitation to produce seeds. We detected pollinator limitation of seed production in D. christmanii but not D. frutescens ssp. frutescens, which we suggest is a function of time-since-disturbance or gap size rather than intrinsic differences between the two species. Both species are self-compatible. Inbreeding depression reduced seed set by 60% in D. frutescens ssp. frutescens but did not occur in D. christmanii. We conclude that pollinator limitation (in fire-suppressed populations of both species) and inbreeding depression (in D. frutescens ssp. frutescens) have the potential to limit seed production in these seed-dependent, rare species. Appropriate fire management should mitigate both of these risks, by maintaining large populations and conditions attractive to pollinators. Although these two species are very similar in reproductive biology, comparisons with other Florida scrub endemics and with rare plants in general suggest that potential threats to conservation via reproductive biology are difficult to predict, depending on combinations of ecology, life-history, and phylogenetic history.
- Menges, E. S., Gordon, D. R., & Evans, M. E. (2003). Reproductive biology of three sympatric endangered plants endemic to Florida scrub. Biological Conservation, 111(2), 235-246. doi:10.1016/s0006-3207(02)00293-8More infoWe investigated the reproductive biology of three plants endemic to rosemary scrub habitats on the Lake Wales Ridge of Florida, USA. We used hand-pollination experiments and observations of flowers and their insect visitors to determine their mating systems and pollination. Fruit or seed set after self pollination was 94, 97, and 8% of fruit or seed set after cross pollination in Eryngium cuneifolium (Apiaceae), Hypericum cumulicola (Hypericaceae), and Liatris ohlingerae (Asteraceae) respectively, indicating that the first two are self-compatible and the last is obligately outcrossing. All three depend on insects for seed production (4–7% fruit or seed set without insects). Diverse insects visit flowers of E. cuneifolium (101 species recorded), whereas L. ohlingerae is visited predominantly by butterflies and H. cumulicola by one genus of bees (Dialictus, Halictidae). Our data indicate pollinator visitation does not currently limit seed production in E. cuneifolium or H. cumulicola, but does in L. ohlingerae. Despite the features they share (habit, habitat, disturbance regime), we found unique aspects of these species’ reproductive biology yielding unique risks to population viability. We suggest that multispecies recovery plans must consider several aspects of the biology of species with superficial similarities to be successful. # 2003 Elsevier Science Ltd. All rights reserved.
- Menges, E. S., Gordon, D. R., Evans, M. E., & Dolan, R. W. (2000). Genetic diversity and reproductive biology in Warea carteri (Brassicaceae), a narrowly endemic Florida scrub annual.. American Journal of Botany, 87(3), 372-381. doi:10.2307/2656633More infoCarter’s mustard ( Warea carteri) is an endangered, fire-stimulated annual endemic of the Lake Wales Ridge, Florida, USA. This species is characterized by seed banks and large fluctuations in plant numbers, with increases occurring in postdisturbance habitat. We investigated the mating system, patterns of isozyme variation, and effective population sizes of W. carteri to better understand its population biology and to comment on reserve designs and management proposals relevant to this species. Warea carteri is self-compatible and autogamous, and probably largely selfing. Measures of genetic variation in W. carteri were lower than values reported for species with similar ecological and life history traits (6.6% of loci polymorphic within populations, 1.87 alleles per polymorphic locus, and 0.026 and 0.018 expected and observed heterozygosity, respectively). The high average value for Nei’s genetic identity (0.989) reflects the paucity of genetic diversity. Genetic variation within populations was not correlated with aboveground population size, effective population size estimates (N e), or recent disturbance history. Much of the diversity detected was found among populations (FST 5 0.304). A significant cline in allele frequencies at one locus and a significant negative correlation between geographic distance and Nei’s genetic identity also point to spatial organization of genetic diversity. As a result we propose that reserve design should include the entire geographic range of W. carteri. We also recommend that the natural fire regime be mimicked.
- Dey, S., Heilman, K. A., Schultz, E. L., Shaw, J. D., DeRose, R. J., Tipton, J. C., & Evans, M. E. (2021). A range-wide network of tree-ring data reveals variation in growth of common pinon across space and time. Ecological Society of America's annual meeting.
- Evans, M. E., DeRose, R. J., Klesse, S., Alexander, M. R., Babst, F., Bouchard, M., Cahoon, S. M., Canham, C. D., Frank, D. C., Girardin, M. P., Gomez, A., Gutierrez-Garcia, G., Villela-Gaytan, S. A., Olds, C., Rayback, S. A., Reid, A., Ricker, M., Schaberg, P. G., Shaw, J. D., & Sullivan, P. F. (2021, December). Enhanced forest ecosystem monitoring for carbon accounting and climate mitigation: the case for adding tree rings to North America’s National Forest Inventories. American Geophysical Union's annual meeting.
- Giebink, C. L., DeRose, R. J., Castle, M., Shaw, J. D., & Evans, M. E. (2021). Tree rings improve growth and yield predictions of a forest management tool. American Geophysical Union's annual meeting.
- Giebink, C. L., DeRose, R. J., Castle, M., Shaw, J. D., & Evans, M. E. (2021). Tree rings improve growth and yield predictions of a forest management tool. Society of American Foresters annual meeting.
- Heilman, K. A., DeRose, R. J., Shaw, J. D., Finley, A. O., Dietze, M. C., Aragon, J., Gray, A. T., Arizpe, A., Klesse, S., & Evans, M. E. (2021). Fusing tree ring and forest inventory data for ecological forecasting of tree growth responses to climate change. American Association of Geographers. Virtual.
- Heilman, K. A., Dietze, M. C., Finley, A. O., Arizpe, A., Aragon, J., Gray, A. T., Klesse, S., Shaw, J. D., DeRose, R. J., & Evans, M. E. (2021). Carbon accounting of ponderosa pine forests across the interior western U. S. based on tree-ring and forest inventory data: drivers of carbon stock and flux and their uncertainties. Ecological Society of America's annual meeting. virtual.
- Babst, F., & Evans, M. E. (2020, August). Hotspots of change in major tree species under climate warming. Annual Meeting of the Ecological Society of America. held virtually: Ecological Society of America.More infoBackground/Question/MethodsWarming alters the variability and trajectories of tree growth around the world by intensifying or alleviating energy and water limitation. This insight from regional to global-scale research emphasizes the susceptibility of forest ecosystems and resources to climate change. However, globally-derived estimates are not necessarily meaningful for local nature conservation or management considerations, if they lack specific information on present or prospective tree species habitats. This is particularly the case towards the edge of their distribution, where shifts in growth trajectories may be imminent or already occurring. Importantly, the geographic space occupied by a tree species is not only constrained by climate, but often reflects biotic pressure such as competition for resources with other species. Hence, distinguishing climatic from competitive niche boundaries becomes a central challenge to identifying areas where tree species are most susceptible to climate change.Here, we employ a novel concept to characterize each position within a species’ bioclimatic niche based on two criteria: a climate sensitivity index (CSI) and a habitat occupancy index (HOI). The CSI is derived from step-wise multiple linear regression models that explain variability in annual radial tree growth as a function of monthly climate anomalies. The HOI is based on an ensemble of five species distribution models calculated from a combination of observed species occurrences and twenty-five bioclimatic variables.Results/ConclusionsWe calculated these two indices for 11 widespread tree species across the Northern Hemisphere. The combination of climate sensitivity and habitat suitability indicated hotspots of change, where tree growth is mainly limited by competition (low HOI and low CSI), as well as areas that are particularly sensitive to climate variability (low HOI and high CSI). In the former, we expect that forest management geared towards adjusting the competitive balance between several candidate species will be most effective under changing environmental conditions. In the latter areas, selecting particularly drought-tolerant accessions of a given species may reduce forest susceptibility to the predicted warming and drying.
- DeRose, R. J., Evans, M. E., & Klesse, S. (2020, August). Building the North American National Forest Inventory tree-ring database. Annual Meeting of the Ecological Society of America. held virtually: Ecological Society of America.
- Evans, M. E. (2020, August). Continental-scale tree ring-based projection of Douglas-fir growth - Testing the limits of space-for-time substitution. Annual Meeting of the Ecological Society of America. held virtually: Ecological Society of America.More infoBackground/Question/MethodsA central challenge in global change research is the projection of the future behavior of a system based upon past observations. Tree-ring data have been used increasingly over the last decade to project tree growth and forest ecosystem vulnerability under future climate conditions. But how can the response of tree growth to past climate variation predict the future, when the future does not look like the past? Space-for-time substitution (SFTS) is one way to overcome the problem of extrapolation: the response at a given location in a warmer future is assumed to follow the response at a warmer location today.Here we developed and evaluated a SFTS approach to projecting future growth of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco), a species that occupies an exceptionally large environmental and geographic space in North America – from 17°N to 55°N in latitude, and across mean annual temperatures ranging from -0.5 to 19.5°C and cumulative annual precipitation from 300 to 4800 mm. We compiled a dataset of 30,388 tree-ring time series from 2,699 sampling sites, totaling 2,706,098 ring widths over the 1902-2016 period of analysis. We then fit a hierarchical mixed effects model to these data to evaluate variation in individual tree growth in response to spatial and temporal variation in climate.Results/ConclusionsWe found opposing gradients of productivity and climate sensitivity, with largest growth rings and weakest response to interannual climate variation in the mesic coastal part of Douglas-fir’s range vs. narrower rings and stronger climate sensitivity across the semi-arid interior. Ring width variation in response to spatial vs. temporal temperature variation was opposite in sign: across space, average ring width was greater at warmer locations, but at a given location, ring widths were almost always smaller in response to warmer-than-average temperatures. This suggests that spatial variation in productivity, which is caused at least partly by local adaptation and other slow processes, cannot appropriately be used to anticipate changes in productivity caused by rapid climate change. We thus adopted an approach substituting only climate sensitivities when projecting future tree growth. Under this approach to SFTS, growth declines were projected across much of Douglas-fir’s distribution, with largest relative decreases in the semiarid U.S. Interior West and smallest in the mesic Pacific Northwest. Better understanding of the limits of SFTS is critical for ecological forecasting in a nonstationary world.
- Heilman, K. A., Dietze, M. C., Shaw, J. D., DeRose, R. J., Klesse, S., Finley, A. O., Gray, A. T., Arizpe, A. H., & Evans, M. E. (2020, August). Assimilation of tree ring and forest inventory data to forecast future growth responses of Pinus ponderosa. Ecological Society of America. Virtual: Ecological Society of America.More infoBackground/Question/MethodsForest responses to future climate are highly uncertain, but critical for forecasting and managing for forest carbon dynamics. To improve ecological forecasts of forest response, we harness the strengths of two large ecological datasets: tree-ring time series data that provide annually resolved growth responses, and spatially extensive forest inventory (FIA) data. We use a Bayesian state space model to assimilate these two ecological data sets, and quantify the effects of precipitation, maximum temperature, tree size, stand density, site index and two-way interactions between these factors on tree growth. We implemented a two-stage approach to model Pinus ponderosa responses in Arizona. Stage 1 leverages tree-ring increment data and repeat diameter measurements of 515 trees to estimate effects on tree growth. Posterior parameter estimates from stage 1 were then used as priors in stage 2, where data were included from an additional 5,794 trees in the forest inventory that only have repeat bole diameter measurements.Results/ConclusionsPrecipitation has a strong positive effect on Pinus ponderosa growth in Arizona, leading to growth declines under drier future conditions. Maximum temperature does not have a strong direct effect on growth, but a positive interaction between temperature and precipitation drives decreased growth under hot and dry future conditions. Tree size, stand density, and site factors all have considerable direct effects on annual tree growth, and can modify climate responses, such that larger trees and trees with high site quality have greater growth increments, but high stand density reduces growth increments, particularly at high temperatures. Interactions between stand-level properties and climate sensitivity provide opportunities to manage for forests that optimize carbon storage and climate resilience. Fusing information from 5794 repeat diameter measurements reduces uncertainty about stand-level processes, and allows us to forecast annual growth increment in forest plots without tree ring data. Assimilating tree ring and forest inventory data can help inform current management, constrain uncertainties about the effects of climate change, and provides a framework for iterative ecological forecasts.
- Riordan, E. C., & Evans, M. E. (2020, August). Spatial data aggregation underestimates variability in tree-growth response to climate. Annual Meeting of the Ecological Society of America. held virtually: Ecological Society of America.More infoBackground/Question/MethodsIncreasingly, scientists are using tree growth–climate relationships quantified from tree-ring data to spatially project climate change impacts on forests, from local to global scales. Local ring-width measurements are often combined through statistical aggregation to represent larger regions. Aggregation maximizes the common climate signal in tree-ring time-series while dampening local factors such that climate emerges as a strong predictor of variability in ring-widths, particularly at broad spatial scales. We ask whether spatial aggregation of ring-width data influences estimates of tree growth–climate sensitivity and biases projections of future forest response to climate change. We aggregated plot-level annual ring-width time-series of Douglas-fir in the southwestern United States, collected by the USFS Forest Inventory Analysis (FIA) program, and corresponding climate data from small (e.g., 40 km grain) to large (e.g., 600 km grain) spatial scales. We then modeled aggregated annual ring-widths as a function of aggregated annual warm season temperature and cool season precipitation, two important drivers of tree growth in the region identified by earlier research.Results/ConclusionsAs aggregation scale increased, so did the proportion of variation in ring-widths explained by climate (coefficient of determination). This was not accompanied by an increase in the magnitude of climate sensitivity (regression slopes), which remained stable, on average, across aggregation scales. Rather, increasing aggregation scale resulted in a strong reduction in the variability of regression slope estimates. The fine scale heterogeneity in climate sensitivity was partially explained by climatic conditions (normals) that vary geographically, with greater tree growth–climate sensitivity at warmer and drier locations. While we did not find an effect of aggregation on the average change in ring-width predicted under future climate scenarios, the decreased variability of climate sensitivity estimates at large spatial scales resulted in predictions that underestimate the variability of future tree growth response to climate. Detecting such landscape-level heterogeneity in climate sensitivity may be particularly important for understanding and managing forest resilience to climate change -- i.e., identifying and actively managing climate refugia. Hierarchical models, which can draw inference from local tree growth and nest effects from multiple spatial scales, may offer a more robust alternative to widely used spatial data aggregation practices.
- Schultz, E. L., & Evans, M. E. (2020, August). Incorporating large-scale disturbances into demographic range models: The importance of fire as a factor limiting the distribution of Pinus edulis. Annual Meeting of the Ecological Society of America. held virtually: Ecological Society of America.More infoBackground/Question/MethodsMaking accurate predictions about species’ future distributions requires a holistic understanding of the factors that determine species range limits. Previous studies of range limits have focused primarily on the direct effects of climate and competition as drivers of range limits. However, climate may also play an indirect role in shaping species distributions via its effect on disturbance regimes. Indeed, previous research on P. edulis demonstrated that climate and competition together were not enough to explain the geographic distribution: projected population growth rates were high at high-elevation locations where climate is was favorable but P. edulis is absent. Here, we used a stochastic demographic range model to evaluate the role of disturbance, particularly fire, as a factor influencing the geographic distribution of Pinus edulis, a tree species at the arid edge of the forest biome. We parameterized the model with census data on 23,426 trees in 1,941 forest inventory plots and incorporated fire as a stochastic disturbance based on fire occurrence data. We then projected the expected P. edulis distribution based on its long-term demographic performance.Results/ConclusionsFire damage was observed in more frequently in plots where P. edulis was absent than in plots where P. edulis was present (4.7% vs 1.7%). In plots that experienced fire, mortality rates of P. edulis were 54.9% in plots experiencing only ground fire damage, 78.6% in plots experiencing ground fire and crown fire damage, and 96.5% in plots experiencing crown fire damage, suggesting that fire can be a major driver of mortality in P. edulis. Applying stochastic fire return intervals (FRI) characteristic of three forest types of the Colorado Plateau region – Ponderosa pine, mixed conifer, and spruce-fir forests – we find that the long-term stochastic growth rate of P. edulis in the presence of fire is below the replacement level of 1.0 in the two forest types with lower FRI. While the direct effects of climate are an important driver of geographic distributions, the fundamental Earth system process of fire is likely necessary to explain P. edulis’ distribution. Cross-scale interactions between climate and disturbance can lead to complex dynamics that are not predictable from models that include only climate and competition.
- Evans, M. E. (2019, September). Demographic range modeling reveals that climate and competition are insufficient to explain a species’ distribution.. 1) annual meeting of the Ecological Society of America, Aug, 2018, New Orleans, LA; 2) MountainClim meeting, September, 2018, Crested Butte, CO; 3) US Forest Service FIA Stakeholder Science Meeting, November, 2019, Knoxville, TN.
- Giebink, C., DeRose, R. J., Castle, M., Shaw, J. D., & Evans, M. E. (2019, November). Updating the Forest Vegetation Simulator with climate response recorded in tree rings. U. S. Forest Service Forest Inventory and Analysis (FIA) Stakeholder Science Meeting. Knoxville, Tennessee: U. S. D. A. Forest Service.
- Klesse, S., & Evans, M. E. (2019, May). Back to the future - Continental-scale tree-ring based projection of Douglas-fir growth. 1) WorldDendro (February 2018, Bhutan), 2) Ecological Society of America's Annual meeting (August 2018, New Orleans, Louisiana), 3) TRACE conference (May 2019, San Leucio, Italy). San Leucio, Caserta, italy: PAGES.
- Evans, M. E., Dietze, M., DeRose, R. J., & Arizpe, A. (2018, February). Lightning Talks on Ecological Networks, Knowledge, and Forecasts. Ecological Knowledge and Predictions: Integrating across Networks and National Observatories. University of Arizona: National Science Foundation.
- Babst, F., Bouriaud, O., Poulter, B., Zhang, Z., Trouet, V. M., Evans, M. E., Charney, N., Record, S., Enquist, B. J., Seftigen, K., Bjorklund, J., Klesse, S., Bodesheim, P., Mahecha, M., Girardin, M., Friend, A., & Frank, D. C. (2017, April). When tree rings go global: challenges and opportunities for retro- and prospective insights. European Geosciences Union General Assembly. Vienna, Austria: European Geosciences Union.
- Evans, M. E., DeRose, R. J., Klesse, S., Aragon, J., Grey, A., Pillet, M., Arizpe, A., Shaw, J., & Dietze, M. (2017, Aug-Dec). Assimilation of tree-ring and forest inventory data to understand the influences of climate, tree size, and stand density on tree growth: a regional analysis of Pinus ponderosa. 1) Ecological Society of America's Annual Meeting, 2) Forest Inventory and Analysis Stakeholder Science Meeting, and 3) Uncertainty Quantification Group, Mathematics Department, University of Arizona. 1) Portland, Oregon, 2) Park City, Utah, and 3) Tucson, Arizona: 1) Ecological Society of America, 2) U. S. Forest Service, 3) Department of Mathematics, University of Arizona.
- Itter, M. S., Bradford, J. B., D'Amato, A. W., Evans, M. E., Finley, A. O., Foster, J. R., & Palik, B. J. (2017, August). Assimilation of tree-ring and repeat census data to model interactions between climate and past forest dynamics. Ecological Society of America's Annual Meeting. Portland, Oregon: Ecological Society of America.
- Klesse, S., DeRose, R. J., & Evans, M. E. (2017, August). Differences in sampling design influence tree-ring derived climate sensitivity: implications for forest vulnerability assessment. Ecological Society of America's Annual Meeting. Portland, Oregon: Ecological Society of America.
- Evans, M. E. (2016, June). Resilience ecology from a forest conservation perspective: from historical roots to practical application. Summer School Modeling Environmental Resilience - Agroecology, Climate, Ecology, Ocean, Society. Paris, France: Ecole Normale Superieure.
- Evans, M. E., Falk, D. A., Arizpe, A., Swetnam, T. L., Babst, F., & Holsinger, K. E. (2016, March). Combining tree-ring and forest inventory data to infer climatic niche: a hierarchical Bayesian approach. In Symposium: “Tree rings and dynamic vegetation models.”. Third American Dendrochronology Conference (AmeriDendro 2016). Mendoza, Argentina: Tree Ring Society.
- Evans, M. E., Falk, D. A., Arizpe, A., Swetnam, T. L., Babst, F., & Holsinger, K. E. (2016, October). Forecasting future tree growth from tree-ring data, and combining tree-ring and forest inventory data. Climate Ecology & Tree Growth Workshop. Petersham, Massachusetts: Harvard Forest, Harvard University.
- Heilman, K. A., DeRose, R. J., Shaw, J. D., Finley, A. O., Dietze, M. C., Aragon, J., Gray, A. T., Arizpe, A., Klesse, S., & Evans, M. E. (2021). Fusing tree ring and forest inventory data for ecological forecasting of tree growth responses to climate change. North American Carbon Project. Virtual.
- Heilman, K. A., Dietze, M. C., Finley, A. O., Arizpe, A., Aragon, J., Gray, A. T., Klesse, S., Shaw, J. D., DeRose, R. J., & Evans, M. E. (2021). Carbon accounting of ponderosa pine forests across the interior western U. S. based on tree-ring and forest inventory data: drivers of carbon stock and flux and their uncertainties. American Geophysical Union's annual meeting. New Orleans, Lousiana.
- co-authors, 1., Woodhouse, C. A., Trouet, V. M., Falk, D. A., Breshears, D. D., Evans, M. E., Wall, T., & MacDonald, G. (2021, October). A Consensus Report on Causes of California’s Changing Wildfires by Scientists of the Southwest Climate Adaptation Science Center. Southwest Climate Adaptation Center (SWCASC).