FIELD NOTES

Influence of intraspecific genetic diversity and stoichiometric conditions on interspecific competition in communities of Daphnia in and around Lake Texoma

I arrived at the UOBS on October 15th, 2010. I have previously been a postdoc in the Botany and Plant Pathology Department at Purdue University, where I worked with Michael Zanis on a community genetics project focusing on a pond community of plants and insects, specifically duckweed and the duckweed weevil. I also completed my PhD at Purdue University in 2009, but in the Entomology Department under Brandi Schemerhorn, where my dissertation title was Population genetics of the Hessian fly. Prior to this I graduated from the “other” university, Oklahoma State University, with a bachelor’s degree in Entomology. My current research takes a mixture of approaches from my prior experiences and combines them with the expertise of Dr. Larry Weider and the model system centered on the zooplankton genus, Daphnia (commonly known as the water flea). Specifically, I will assess the genetic diversity and population genetic structure of communities of Daphnia species in and around Lake Texoma, while recording the nutrient ratios (i.e. carbon-nitrogen-phosphorus a.k.a. stoichiometric conditions) in which they are collected. Using these data I will test the correlation between stoichiometric conditions and population genetic structure and the effect intraspecific genetic diversity has on interspecific competition in a daphnid community.

Communities of Daphnia species provide an excellent opportunity to examine the intersection between population and ecological genetics. Additionally, sexual and asexual reproduction and egg banks, augmenting permanent populations, add to the complexity of population genetics of this species and can cause temporal variance in population diversity and structure. This type of complexity leaves the collective understanding on Daphnia population genetic structure in need of further exploration. Conversely, there have been numerous investigations on the factors influencing and shaping community structure and composition, with Daphnia as a portion or the main focus of study. Of these studies, however, direct focus on Daphnia communities and the interaction between species has been neglected.

Many Daphnia species occupy the same habitats at the same time (often competing for food resources, i.e. algae/bacteria), and therefore must interact. Yet, the influence of this interaction on species fitness, and the correlation between this fitness and genetic diversity is an unknown factor. Understanding genetic diversity in association with species interactions within a community has many implications in the evolution of these organisms. Several factors could be influenced by genetic diversity in these communities, including parasite load and interspecific competition. One factor that has been shown to influence genetic composition, and thus genetic diversity, in a Daphnia population is changes in environmental nutrient conditions. Therefore, it will be important to identify the nutrient ratios of each Daphnia community to completely investigate the influence of genetic diversity on community evolution.

Additionally, I am interested in looking at environmentally-relevant genes, in particular, the evolution of the phosphoglucose isomerase (Pgi) gene at the population, community, and genus levels. As Daphnia progresses as a model organism, this particular study will provide evolutionary insight into the role intraspecific genetic diversity has on interspecific competition.

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