PARENT SESSION
Poster Session 3: Aquatic Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 210 D, Level 2, Palais des congrès de Montréal
Measuring competition among predatory aquatic insects.
Sircom, Julie*,1, Walde, Sandra1, 1 Dalhousie University, Halifax, NS
ABSTRACT- One of the fundamental questions in ecology concerns the maintenance of species diversity. Most of the proposed mechanisms focus on either the local (single community) or regional (metacommunity) scale, although there is general agreement that processes at both scales operate together to produce local diversity patterns. The maintenance of diversity within trophic levels usually involves the amelioration of competition, and theory proposes mechanisms at both the local and regional scale that can allow coexistence. We are examining coexistence mechanisms at local and regional scales in a set of small streams, with no direct connections, that drain into the Bay of Fundy (Nova Scotia, Canada). Invertebrate predators (principally Chloroperlidae, Perlodidae and Rhyacophilidae) occur in very different relative densities across streams. This variation may be the result of differing local environment (local mechanisms) and/or the result of stochastic adult movement among streams (regional mechanisms). As the first step, we have used temporal census data to estimate competition coefficients for species pairs in 8 streams. The method is based on the Lotka-Volterra competition equations, and involves a multiple regression of population change in one species against the populations of both (population estimates can be numbers or biomass). We use these coefficients and our knowledge of the different stream environments (e.g. nutrient loading, prey community, presence of fish) to determine which factors appear to favor one species over the other at the local scale.
Key words: competition, coexistence, Plecoptera, Trichoptera