Testing how species interactions and evolution accelerate or decelerate climate-driven range shifts

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Globally many species' ranges are shifting poleward and up in elevation. However, most observed range shifts are less than we would predict if species were perfectly tracking climate, and they differ substantially, with some moving in idiosyncratic directions and others not moving at all. My long-term objective is to explain which species lag behind climate change and why to better predict and manage impacts on biodiversity. My short-term objectives are to investigate how climate-driven range shifts are accelerated or decelerated by (1) species interactions, (2) evolutionary dynamics and (3) feedbacks between the two. (1) Variation in climate tracking will arise if species differ in how interactions with other species affect rates of spread (at expanding edges of range shifts) and decline (at contracting edges). For example, some species might be unable to colonize areas that have become climatically suitable but contain better competitors. The proposed work will experimentally manipulate key species interactions, seed predation and competition, along climate gradients spanning 30 plants' elevation ranges in the Cascade Mountains, to determine whether certain functional groups or range edges are more influenced by species interactions. (2) In theory evolution can have diverse effects on range shifts, such as accelerating range expansion as better dispersers concentrate and mate at expanding range edges, decelerating range expansion as harmful mutations increase by chance in small populations at expanding range edges, or decelerating rates of range contraction if populations are able to rapidly adapt to deteriorating conditions. The proposed work will test whether variation in rates of range expansion within and among monkeyflower species is related to differences in accumulation of deleterious mutations. It will also measure the demographic effects of trait evolution to determine whether rapid adaptation to extreme climatic perturbation can rescue populations and prevent range contraction. (3) Species interactions could modify evolutionary responses to climate change in ways that are unpredictable without examining their feedbacks. For example, competition could accelerate rapid adaptation to a changing environment by causing additional selection, despite reducing population size, or alleviate the build-up of deleterious mutations at expanding edges by slowing rates of range expansion, allowing larger population sizes and genetic diversity to build up. We will use novel lab microcosms with duckweeds to study how species interactions affect range evolution along a moving temperature gradient. The research will involve international collaboration, advanced skill development, and networking for 1 postdoctoral, 5 graduate, and 10 undergraduate trainees. Trainees will be equipped with transferable skills for careers in private sector, government, or academia, and knowledge to help address the ecological impacts of climate change in Canada.