CAREER: A Size-Based Test of Species-Energy Theory in Stream Ecosystems - Linking Individuals, Communities, and Underrepresented Minorities

Virginia Commonwealth University, Richmond VA

Investigators

Abstract

There is a well-established pattern of biodiversity on Earth, with highest biodiversity found in the tropics and a decrease in biodiversity with increasing latitude towards the poles. Ecologists have suggested that the reason for this pattern is that higher levels of food resources for life are found in the tropics. This project will perform a direct test of that hypothesis by making measurements of biodiversity and food resource levels in streams across a broad latitudinal gradient. In each of eight study regions, fishes and invertebrates will be intensively sampled. The data will be used by the researcher to develop mathematical models of the relationships between the average size of individuals and the abundance of those individuals within a community as a means of testing the idea about biodiversity and resources. This project will also focus on engaging underrepresented minorities in freshwater research. In each of four years, a group of three minority undergraduates will be trained to conduct stream surveys, to analyze original data, and to present results at the annual meeting of the Society for Freshwater Science, for a total of 12 undergraduates mentored throughout the project. One Ph.D. student identified as an underrepresented minority student also will be trained to compete for leadership-level positions in environmental research or management. An empirical test of species-energy theory within stream ecosystems will be conducted in three steps. In Step-1, size-spectra (scaling relationships between average individual body mass and population abundance) will be quantified in each of the eight study regions and used to model the distribution of abundance among primary, secondary, and tertiary consumers. Nitrogen stable isotope samples and published feeding behaviors will also be used to assess whether trophic position is a consistent function of body size. Systematic, among-site comparisons of size-spectra models will then test whether the scaling of abundance with individual body mass and trophic position is constant among tropical and temperate streams. In Step-2, species-abundance distributions will be compiled for each study stream then compared among streams to assess whether species richness increases more rapidly, relative to a constant number of individuals, in tropical streams. In Step-3, supplementary fish and invertebrate data from National Ecological Observatory Network streams will be used to test for seasonal or inter-annual differences in the size-spectra and species-abundance distribution models.