Ecology and evolution of young species in sympatry

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Biodiversity varies dramatically across the world and Canada, and performs important functions and services for Canadians. Biodiversity forms when populations of one species diverge from one another, typically in geographic isolation (allopatry), and eventually come back into secondary contact and overlap (sympatry), augmenting local and regional biodiversity. The focus of our research is secondary sympatry - how do young species live together, and how do they influence each other's ecology and evolution? An answer to these questions is important - we must understand how biodiversity forms and is maintained if we are to protect it. The specific objective of the proposed research is to test the consequences of secondary contact and sympatry among young species for traits involved in (I) species recognition and (II) ecology. We use birds to address these questions because the distribution, taxonomy, and evolutionary relationships of birds are better known than any other group. (I) Species Recognition Traits - Our previous work documented greater divergence in traits involved in species recognition (colour patterns and songs) when closely related species of birds live in sympatry. We propose to test among alternative hypotheses to explain this pattern (hybridization, aggression, signal interference, indirect selection through ecological traits) using comparative and experimental studies. (II) Ecological Traits - Our previous work on the ecology of young species suggests that closely related birds initially use similar habitats and overlap breeding territories, and then subsequently diverge in habitat use. We will test the Character Displacement Hypothesis to explain habitat divergence, using experiments to examine fitness costs and selective pressures acting on pairs of young species that live together, representing three distinct families of songbirds. Together, our research will test the importance of interactions among young species during the formation of biodiversity, providing important insights into how and how often closely related species influence each others' ecology and evolution, and, more broadly, how interactions among closely related species promote or constrain local biodiversity.