Waiting on a mule deer crossing…
Climate change is imposing novel selection, disrupting local adaptation, shifting geographic distributions, and altering species composition and diversity of ecological communities. Accordingly, climate change acts directly on species through new abiotic conditions, as well as indirectly through altered biotic interactions. Here, we seek to test mechanistic hypotheses about evolution in complex environments where correlated suites of traits evolve in response to abiotic and biotic agents of selection. Specifically, we propose to examine the mechanistic basis of local adaptation to current abiotic and biotic conditions in the emerging ecological model plant, Boechera stricta (Brassicaceae), in the Colorado Rocky Mountains. We focus on plant-herbivore interactions, as they provide exceptional opportunities for dissecting the direct and indirect effects of climate change. We will then predict plant evolutionary responses to projected future abiotic and biotic environments. To evaluate how abiotic conditions and the biotic community have interacted to shape local adaptation and exert selection on functional traits (Aim 1), we will first conduct a multifactorial manipulation of herbivory, snow dynamics, and water availability in three field gardens at different elevations. We will then characterize herbivore communities across elevational gradients to project future distributions and abundances (Aim 2). Finally, based on these projections, we will investigate how adaptive landscapes will shift under climate change by exposing B. stricta transplants to current and future abiotic conditions and herbivore levels in high and low elevation gardens (Aim 3 and 4). We hypothesize that climate change favors novel suites of traits, such as the rapid development of high elevation families combined with the drought tolerance and herbivore resistance of low elevation families. Further, to test the hypothesis that genetic trade-offs restrict adaptation, we will contrast natural accessions with existing genetic constraints vs. recombinant inbred lines that allow an unconstrained response to selection. Finally, we will examine the genetic basis of local adaptation by mapping quantitative trait loci and test whether the fitness of local alleles declines under climate change. Despite extensive work characterizing local adaptation, we still know little about the processes through which species adapt to the simultaneous, likely interactive, effects of multiple abiotic and biotic agents of selection. Dissecting the contributions of climatic and biotic factors to local adaptation and selection will enable us to forecast how climate change could alter adaptive evolution and influence the risk of extinction. The proposed studies will reveal the extent to which climate change could favor novel suites of traits, whether genetic constraints could restrict adaptation, and whether climate change could increase the vulnerability of local populations to decline. Collectively, our field experiments will identify the functional traits and genetic basis of local adaptation to complex environments and evaluate the evolutionary and ecological consequences of projected future, novel environments.
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