Testing the Climate Variability Hypothesis in coast-inland systems using the widespread plant Erythranthe guttata

The Climate Variability Hypothesis (CVH) states that organisms in more climatically variable environments are adapted to a wider range of climatic conditions than organisms in less variable environments. The CVH was conceived to explain consistent trends of higher diversity and smaller geographic ranges in the tropics compared to temperate environments. Yet, the underlying assumption that organisms exposed to greater variability will have wider niches can be applied more broadly. Due to marine influence, coastal areas typically experience smaller temperature fluctuations relative to inland areas. According to the CVH, we expect coastal organisms to have more narrow thermal niches because they experience a smaller range of temperatures. We tested the CVH in a novel setting by comparing the thermal niches of coastal and inland populations of Erythranthe guttata using a growth chamber experiment. Preliminary data indicate that inland populations have larger thermal niches than coastal populations, though this does not conform exactly to the CVH. Inland populations performed no better at lower temperatures than coastal populations, though they experience these temperatures more often. This is likely due to physiological limits on performance at these temperatures. Inland populations had higher relative growth rate under higher temperatures, as predicted by the CVH. This holds implications beyond the CVH. If coastal organisms have more narrow thermal niches, they may be more sensitive to temperature increases from climate change. We are continuing this research by using a mechanistic model to understand shifts in suitable habitat for coastal and inland populations and how these populations may respond differently to climate change

Testing the Climatic Variability Hypothesis with coastal and inland populations of Mimulus guttatus and implications for these populations under climate change

How climate shapes the niche of a species is a core interest in evolution and ecology. Research on the evolution of climatic niches can inform us on the historical relationship between organisms and their climate, and, in an era of great environmental change, what that relationship may look like in the future. In this study, I tested an essential idea in the history of climate niche research, the Climatic Variability Hypothesis, by comparing the thermal niche breadth of coastal and inland populations of Mimulus guttatus. Using thermal performance results from this experiment, I also forecasted how the suitability of thermal habitat may change for these populations. Unexpectedly, coastal and inland populations did not differ in thermal niche breadth. All populations possess relatively wide performance curves. However, I found other interesting differences in their thermal performance curves that are deserving of further research. Because populations differed little in their performance curves, they all show similar responses to temperature increases. These increases are actually projected to bring more favorable thermal conditions for all populations. However, this is only assuming that plants have plentiful water. Drier conditions caused by climate change may outweigh benefits from warmer temperatures. Of course, measuring and quantifying the climatic niche of an organism and predicting its future are complex tasks. I introduce what I hope are improvements, if only minor, to methods that have previously been used

Differences in thermal niche between coastal and inland populations of the yellow monkeyflower (Mimulus guttatus)

Climate change will have multiple important impacts on coastal plant communities, yet how coastal plants will respond to temperature increases is understudied. Coastal areas experience small fluctuations in temperature daily and annually, similar to lowland tropical environments where research has shown that some tropical organisms are extremely threatened by increases in temperature because their thermal environmental has, historically, been very stable. Using multiple approaches, we plan to study if coastal and inland populations of the plant Mimulus guttatus differ in the evolution of their thermal niches. Are coastal populations more sensitive to changes in temperature, have coastal populations been limited in their thermal niche evolution, and are coastal populations more vulnerable to climate change? To test these questions, we have compared the evolution of habitat and temperature seasonality on a phylogeny of populations across the range of M. guttatus. We plan to compare relative growth rate between coastal and inland populations under different temperature treatments in growth chambers to understand how thermal niche currently differs and predict how populations may fair under climate change

Dental measurement and diet data for mammals

Missing values in measurement data represent specimens for which the dimension could not be measured, either because the image we took of it was not of adequate quality or because that part of the specimen was missing or damaged. See ReadMe file for additional information.,Because teeth are the most easily preserved part of the vertebrate skeleton and are particularly morphologically variable in mammals, studies of fossil mammals rely heavily on dental morphology. Dental morphology is used both for systematics and phylogeny as well as for inferences about paleoecology, diet in particular. We analyze the influence of evolutionary history on our ability to reconstruct diet from dental morphology in the mammalian order Carnivora, and we find that much of our understanding of diet in carnivorans is dependent on the phylogenetic constraints on diet in this clade. Substantial error in estimating diet from dental morphology is present regardless of the morphological data used to make the inference, although more extensive morphological datasets are more accurate in predicting diet than more limited character sets. Unfortunately, including phylogeny in making dietary inferences actually decreases the accuracy of these predictions, showing that dietary predictions from morphology are substantially dependent on the evolutionary constraints on carnivore diet and tooth shape. The “evolutionary ratchet” that drives lineages of carnivorans to evolve greater degrees of hypercarnivory through time actually plays a role in allowing dietary inference from tooth shape, but consequently requires caution in interpreting dietary inference from the teeth fossil carnivores. These difficulties are another reminder of the differences in evolutionary tempo and mode between morphology and ecology.,Dental dimensions measured using digital calipers from specimens in the UC Museum of Vertebrate Zoology, with taxonomy corrected to MSW3 for consistency with phylogenetic data. Specimen-level data includes 2 specimens of each species where available; species-level data is simply one of the specimens with the most complete set of measurements or randomly chosen if both were equally complete. Diet data collected from primary literature as described in paper

Gremer_germinationtimingexper_phenotypeandfitnessdata

Data from the germination timing experimen

Gremer_vernexperiment_phenotypeandfitnessdata

Data for the vernalization experimen

Data from: Germination timing and chilling exposure create contingency in life history and influence fitness in the native wildflower Streptanthus tortuosus

1. The timing of life history events, such as germination and reproduction, influences ecological and selective environments throughout the life cycle. Many organisms evolve responses to seasonal environmental cues to synchronize these key events with favorable conditions. Often the fitness consequences of each life history transition depend on previous and subsequent events in the life cycle. If so, shifts in environmental cues can create cascading effects throughout the life cycle, which can influence fitness, selection on life history traits, and population viability. 2. We examined variation in cue responses for contingent life history expression and fitness in a California native wildflower, Streptanthus tortuosus, by manipulating seasonal germination timing in a common garden experiment. We also manipulated chilling exposure to test the role of vernalization cues for seasonal life history contingency. 3. Plants germinating early in the growing season in autumn were more likely to flower in the first year and less likely to perennate than later germinants in spring. First year reproduction and overall fitness was highest for autumn cohorts. Sensitivity analyses showed that optimal germination date depended on survival beyond the first year and fruit production in later years. 4. Experimental chilling exposure induced first year flowering in spring germinants, demonstrating that seasonal life history contingency is mediated by a vernalization requirement. This requirement reduced fitness of spring germinants without increasing survival or later fecundity and may be maladaptive. Such mismatches between cues and fitness may become more pervasive as predicted climate change reduces exposure to chilling, shortens growing seasons, and increases severity of summer drought. 5. Synthesis: Shifts in germination timing in seasonal environments can cause cascading effects on trait expression and fitness that extend beyond the first year of the life cycle. Climate change is likely to shift seasonal conditions, influencing such life history contingency, with significant impacts on trait expression, fitness, and population persistence. These shifts may cause strong natural selection on cue sensitivity and life history expression, but it is an open question whether populations have the potential for rapid adaptation in response to this selection

Variation in the seasonal germination niche across an elevational gradient: the role of germination cueing in current and future climates

PREMISE:The timing of germination has profound impacts on fitness, population dynamics, and species ranges. Many plants have evolved responses to seasonal environmental cues to time germination with favorable conditions; these responses interact with temporal variation in local climate to drive the seasonal climate niche and may reflect local adaptation. Here, we examined germination responses to temperature cues in Streptanthus tortuosus populations across an elevational gradient. METHODS:Using common garden experiments, we evaluated differences among populations in response to cold stratification (chilling) and germination temperature and related them to observed germination phenology in the field. We then explored how these responses relate to past climate at each site and the implications of those patterns under future climate change. RESULTS:Populations from high elevations had stronger stratification requirements for germination and narrower temperature ranges for germination without stratification. Differences in germination responses corresponded with elevation and variability in seasonal temperature and precipitation across populations. Further, they corresponded with germination phenology in the field; low-elevation populations germinated in the fall without chilling, whereas high-elevation populations germinated after winter chilling and snowmelt in spring and summer. Climate-change forecasts indicate increasing temperatures and decreasing snowpack, which will likely alter germination cues and timing, particularly for high-elevation populations. CONCLUSIONS:The seasonal germination niche for S. tortuosus is highly influenced by temperature and varies across the elevational gradient. Climate change will likely affect germination timing, which may cascade to influence trait expression, fitness, and population persistence

Variation in the seasonal germination niche across an elevational gradient: the role of germination cueing in current and future climates.

PREMISE:The timing of germination has profound impacts on fitness, population dynamics, and species ranges. Many plants have evolved responses to seasonal environmental cues to time germination with favorable conditions; these responses interact with temporal variation in local climate to drive the seasonal climate niche and may reflect local adaptation. Here, we examined germination responses to temperature cues in Streptanthus tortuosus populations across an elevational gradient. METHODS:Using common garden experiments, we evaluated differences among populations in response to cold stratification (chilling) and germination temperature and related them to observed germination phenology in the field. We then explored how these responses relate to past climate at each site and the implications of those patterns under future climate change. RESULTS:Populations from high elevations had stronger stratification requirements for germination and narrower temperature ranges for germination without stratification. Differences in germination responses corresponded with elevation and variability in seasonal temperature and precipitation across populations. Further, they corresponded with germination phenology in the field; low-elevation populations germinated in the fall without chilling, whereas high-elevation populations germinated after winter chilling and snowmelt in spring and summer. Climate-change forecasts indicate increasing temperatures and decreasing snowpack, which will likely alter germination cues and timing, particularly for high-elevation populations. CONCLUSIONS:The seasonal germination niche for S. tortuosus is highly influenced by temperature and varies across the elevational gradient. Climate change will likely affect germination timing, which may cascade to influence trait expression, fitness, and population persistence