Dissertation Research: Eco-Evolutionary Dynamics of the Dilution Effect

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One surprising effect of biological diversity can be to reduce the spread of disease: infection of one host species may be lower in the presence of other host species. This ?dilution effect? is typically seen when the species are similar enough that they compete for resources such as food. The net effect of species diversity then depends on whether diversity reduces infection more than it decreases the availability of resources. This project will investigate the dilution effect using artificial communities of two zooplankton, algae they both eat, and a fungus that infects one of the zooplankton more readily than the other. Previous work with these communities showed that the net effect of the less susceptible zooplankton on the more susceptible one depended on genetic diversity: the higher the genetic diversity of the more susceptible zooplankton, the more beneficial the presence of the less susceptible one. This suggests that rapid evolution of the susceptible zooplankton was required for the dilution effect to operate. Research will now measure how the genetic makeup of the susceptible zooplankton changes as competition and infection proceed, and how the genetic changes result in changes in the traits of the zooplankton to create a dilution effect. Results should increase understanding both of how ecology and evolution can affect each other and how biodiversity can counter disease. The broader impacts of this research include applications to control of disease in wildlife and in humans. Dilution effects may be important in serious diseases such as Lyme disease, West Nile virus, Hantavirus, and schistosomiasis. The project will also provide research experience for undergraduate researchers including members of underrepresented groups.