Evolutionary ecology of species distributions

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No species occurs everywhere. Understanding why not involves questions at the heart of ecology (is habitat use limited by climate? interactions with other species? lack of dispersal?), and evolution (why aren't all species distributions constantly expanding via adaptation?). These questions are also directly related to important conservation problems, including habitat fragmentation, invasions, and climate-change induced range shifts. Theoretical models for range limits far exceed robust tests of their predictions, preventing realistic application of theory to real-world conservation. ***Theory makes contrasting predictions about the ecological and evolutionary role of edge populations depending on the environmental gradient that limits them. My long-term goal is to test for global patterns in the ecological and*evolutionary processes governing species range limits, particularly the role of species interactions. My short-term goals are to test: for global patterns in the ecological gradients (e.g. climate, species interactions) that generate range limits; the prevalence and consequences of adaptation at stable and contracting range edges; and whether the ecological and evolutionary importance of species interactions increases alongside biodiversity. ***I propose experiments at three complementary spatial scales. Experimental manipulations of biotic, abiotic, and genetic factors range will test their relative importance across a herb's elevational range. This has broad implications for the distribution of biodiversity, but has not been established for any species. I will use experimental bacteria evolution across to test whether spatial and temporal variability can create range edges, as predicted by metapopulation models. Artificial range contractions via increasing patch extinction or isolation will test their predicted effect on dispersal evolution. Dispersal evolution at contracting limits could determine how well genetic diversity is maintained during range shifts. Finally, arctic-to-equator experiments, including one from my lab, have recently confirmed that species interaction intensity increases toward low latitudes/elevations. I will expand my experiment to assess whether increased interaction intensity is associated with increased biodiversity, and whether stronger interactions generate increasing selection. These relationships are proposed to explain global patterns in biodiversity but have not been tested at a global scale.***Most Canadian species at risk are edge populations, and Canada has one of the largest latitudinal gradients of any country. The importance of edge populations to species persistence, how edge populations respond to environmental change, and the origin and implications of latitudinal gradients are quintessential Canadian conservation questions.