Trade-offs and Community Structure Along Environmental Gradients: An Experimental and Comparative Approach

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WPC0 2 B V T W #| x 10 pitch z N x x x , x @ ; HP Laserjet (25-in-one, Network) HPLASEII.PRS X t 4 P RN h 0 IS 2 4 V N W #| x Courier 10 pitch z N x x x , x @ ; HP Laserjet (25-in-one, Network) HPLASEII.PRS X t 4 P RN h 0 IS 2 - J . 9307033 McPeek This research addresses why species differ in their responses to dramatic environmental changes by studying a group of aquatic insects, the Coenagrionidae damselflies (Odonata: Zygoptera) in two genera. Some Enallagma species are found as larvae only in ponds and lakes containing fish, while the remaining Enallagma species are found as larvae only in fishless ponds and lakes. In contrast, Ischnura species are abundant in both lake types. The objectives of this research are to quantify the mechanisms and relative strengths of direct and indirect interactions among damselflies, their predators, and their prey in each lake type and to compare these results for the two communities. many current theories explore the consequences of dramatic ecological changes to community structure by assuming that all species at a given trophic level respond similarly. However, comparisons of natural communities show while some species are extirpated and replaced as community structure is changed, other species can persist over wide ranges of ecological conditions. %%% The study will have important ramifications for conserving biodiversity, by identifying key properties of species indication their sensitivity to dramatic ecological changes (e.g, comparable to those accompanying habitat alterations and climate change).