PARENT SESSION
Poster Session #31: Animal Population and Community Ecology I.
Wednesday, August 7. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

How subsidies influence community patterns on both sides of a pond-terrestrial boundary: A census and stable isotope approach.

Kraus, Johanna^*,1, ¹ University of Virginia, Charlottesville, VA

ABSTRACT- Many habitats are energetically linked through organismal and nutrient movement. These movements, or subsidies, have been implicated as an important influence on the abundance and distribution of organisms, especially at the interface of two habitats. Subsidy studies, however, usually focus on the effects of subsidy in only one habitat. This narrow focus overlooks the reciprocal and interconnected nature of many interchanges. To address the potential role of subsidy in driving community patterns on both sides of a habitat boundary, I have begun investigating the distribution and abundance of arthropod taxa in relation to an aquatic-terrestrial edge in small ponds and their terrestrial borders. I used multiple sampling techniques to determine organismal distribution and stable isotopes to indicate the diet source of these organisms. Census data suggests that taxa are not uniformly distributed over a gradient away from the pond edge. Trophic level appears to be a reasonable predictor of this distribution for aquatic but not terrestrial organisms. Terrestrial predators, for example, are uniformly distributed with respect to the edge, but wolf spiders (Lycosidae), a common terrestrial predator, are found in higher densities at the pond edge. Preliminary isotope analysis reveals that on average carbon signature is homogenous among habitats, which suggests a large role of allochthonous input in these habitats. Closer analysis suggests that organismal and nutrient input from terrestrial to aquatic may dominate the flow, but more samples are needed before a conclusion can be reached. This study uncovers initial evidence of community patterns that are influenced by reciprocal subsidies between a pond and the surrounding terrestrial habitat. Further sampling and manipulation in this system is proposed to more fully address the role of these subsidies and their differential role in influencing community patterns and processes in terrestrial and aquatic communities.

KEY WORDS: subsidy, community, arthropod, stable isotopes