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The role of dominant species in the structure and function of ecosystems

Many communities are characterized by uneven distributions of species. Understanding the processes underlying these patterns and their implications for community dynamics and ecosystem function is a central endeavor of ecology. Often in communities only a few species are very common (or dominant), whereas a majority of species occur at moderate or low abundance (subordinate or rare). Dominant species generally garner a disproportionate share of resources, contribute most to productivity and other ecosystem functions, and are consistently present in the community over time. Rare and uncommon species, on the other hand, are collectively the most diverse component of the community, but generally contribute less to ecosystem functioning (although there are exceptions, e.g., legumes) and often experience high levels of turnover.

Our research in tallgrass prairie suggests that dominant species (i.e., a few common C4 grasses) can strongly influence diversity, and it is through the impacts of disturbances on their abundance that variation in community attributes and ecosystem processes in space and time are observed. Moreover, our research indicates that these dominant species play a central role in the maintenance of ecosystem function (Smith and Knapp 2003), and that the dominant species are important in determining resistance of communities to invasion (Smith and Knapp 1999, Smith et al. 2004). Because of the key role dominant species appear to play as drivers of community dynamics and ecosystem function, our research seeks to gain a more general understanding their role in ecosystems by melding genetic and ecological information. We are currently examining how Andropogon gerardii, the dominant grass species in tallgrass prairie, influences community characteristics (diversity) and ecosystem function (productivity). Our approach links genetic variation in A. gerardii to ecological responses of this species to environmental changes (climate change, disturbances such as fire), as well as how this genetic variation may impact invasion. Our plan for the future is to expand this research to include the co-dominant grass species, Sorghastrum nutans, and examine how genetic variation in the two co-dominants is altered by key aspects of climate change (precipitation variability, warming and climate extremes), and in turn how this variation at the genetic and phenotypic level affects community and ecosystem processes.

Other Current Initiatives