Population consequences of sexually dimorphic responses in a plant species to ongoing and experimental changes in climate

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Predicting how a population of organisms will respond to changes in the climate they experience requires understanding how small-scale changes in ecological processes translate to patterns at broad scales. Most studies of biological responses to environmental change have either documented the natural pattern of whole-species response to past change or, alternatively, the effects of experimentally manipulated environment on the performance of a few individuals. The former approach benefits from its realism, but is too coarse to elucidate the physiological responses underlying the response to changes in climate. The latter approach demonstrates these mechanisms in detail, but does so at small spatial scales and under artificially simplified experimental conditions. This study seeks to bridge these two approaches, studying the responses of the plant Valeriana edulis to climatic variation at field sites in the Colorado Rockies. Individuals of this species have separate sexes (i.e. are either male or female) and the sexes respond differently to changes in climate. The researchers will investigate how these variable, individual-level responses to climate scale up to determine population dynamics and species persistence. This work will be conducted at the Rocky Mountain Biological Laboratory (RMBL) using historic and contemporary demographic data to compare the effects of a changing climate over space (an 1800 m elevational gradient), between experimental manipulations (warming and snow removal), and over time (40 year record). This study also provides opportunities for education and outreach through undergraduate and graduate scientific training, citizen science initiatives, and through the development of web-based curricula in collaboration with the RMBL.This research asks whether the sex-mediated physiological response of males and females in dioecious species to changes in climate can skew population structure (sex ratios) with resultant demographic consequences. The researchers will construct size- and sex-structured demographic models using historic and contemporary data on vital rates, mating functions, water use efficiency and primary (seed) sex ratio for populations under (1) historic climate, (2) contemporary climate over the species' elevation range, and (3) experimental warming and snow removal. Using model selection and life table response experiment analyses, this study assesses the overall consequences of spatial (1800 m elevation), temporal (past vs. present) and manipulated (present vs. simulated future) variation in climate for population performance, as well as the specific contribution of (and physiological basis to) climate-skewed sex ratios.