UBC Theses and Dissertations

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UBC Theses and Dissertations

Community context of adaptation to environmental change Kleynhans, Elizabeth J.


Humans are causing rapid changes to the biotic and abiotic conditions on Earth. My thesis investigates how competition might shape adaptation to an altered environment. Intraspecific competition creates diversifying selection, which alters the genetic variation available for adaptation. Using an individual-based model, I found that intraspecific variation altered the genetic variance-covariance matrix by pushing standing genetic variation to more closely resemble available resources. This changed the “genetic line of least resistance” so that standing genetic variation and de novo mutation both provided possibilities for evolutionary rescue in different directions. Competition between species can also influence evolution to abiotic change. Using an individual-based model I found that differences in population size and competitive ability, between two species, could facilitate coexistence and in some cases cause evolution to occur in the opposite direction to that predicted from environmental change. In an empirical setting, I asked whether species diversity may alter adaptation to abiotic change by changing population size, increasing genetic diversity, and/or by altering selection experienced by a focal species. Using a reciprocal transplant experiment on grasses evolved for 14 years under ambient and elevated CO₂ conditions, in communities of low or high species-richness, I found that the biological community altered the nature of selection in elevated CO₂, so that adaptation was observed primarily when species were grown in a community similar to the one in which they were previously selected. Lastly, I tested whether functional traits of species observed today might reflect differences in the nature of selection experienced in different biotic and abiotic environments. In contrast to expectation I only found the main effects of species diversity and abiotic change to influence plant functional traits. Overall, my research highlights an important role for species interactions in altering adaptation to abiotic environmental change, which cannot be overlooked when predicting how species will adapt to climate change.

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