Dissertation Research: Testing for Disruptive Competition in Solitary Populations of the Three-spined Stickleback

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Wainwright0105147Sympatric speciation, in which a single population undergoes an evolutionary split into two co-occurring species, has been a source of controversy for 50 years. Many biologists believe species split only when populations are geographically divided. Skepticism about sympatric speciation is due to theoretical criticisms and the paucity of unambiguous examples. The idea has regained acceptance lately, due to accumulating empirical examples and supportive theoretical analyses. However, the theory relies on population dynamics that have never been soundly demonstrated in nature. The hypothesis is that competition among individuals in a population is strongest among common phenotypes, weakest for rare phenotypes, so that the average individual does poorly while unusual individuals escape competition and do relatively well. The investigators will use observational surveys to test whether such disruptive selection occurs naturally in populations of freshwater stickleback fish. They will also conduct experimental population density manipulations to test whether competition is the underlying cause. This research will test the assumptions underlying recent advances in speciation theory. It is also relevant to understanding how individuals in a population subdivide their resources, which affects both population dynamics, and how an invading species adapts to a new environment.