DISSERTATION RESEARCH: Community assembly across regional diversity and latitudinal gradients

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Humans depend on biodiversity for countless goods and services, and it is thus essential that we understand the processes that regulate diversity in space and time. For example, it has long been recognized that the number of species generally increases towards the equator, and scientists have historically assumed that this ?latitudinal diversity gradient? results from variation in environmental factors or changes in how species interact with each other. Consequently, research on this topic has explored how diversity and latitude relate to nearly everything imaginable. This body of work has ignored a simple alternative explanation: random processes. In particular, the accidental arrival of a new individual or the random extinction of a small population can make a big difference in what species happen to live in a certain place. Some scientists now believe that the effect of such random events may vary with latitude and diversity. The goal of this research, therefore, is to determine how important these random versus more predictable processes are in determining where species occur. This will be achieved by collecting data from natural aquatic communities and conducting outdoor experiments across a several sites and latitudes in North America. This project also provides several opportunities for undergraduate and high school students to become actively involved in ecological research. Two undergraduate students will be taken on cross-continental sampling trips and will be mentored on independent projects that relate to this research. The experimental work incorporates several students from St Louis high schools, who not only work directly with the researchers on this project, but also get exposure to other projects at Washington University. Finally, one aspect of this project is collecting data for natural communities over multiple sites and years across a latitudinal gradient. Such large data sets with standardized sampling methods replicated in space and time are relatively rare, yet are absolutely necessary to understand large-scale patterns of biodiversity. The data generated from this project will be added to a publicly available database through Washington University?s Tyson Research Center, giving access to anyone interested.