Trophic level distribution of ephemeral pool insects: Uniformity among pools

Abstract

We collected aquatic insects from three types of ephemeral pools (grassland, road, and woodland) in attempt to determine the trophic structure and trophic level distribution of insect communities. Each specimen was assigned to one of several trophic levels including carnivore, detritivore, herbivore, or some combination of these. Trophic level proportions were then compared for all pool classes; six of seven trophic level proportions were the same (P≥0.05; except herbivores. P=0.01) in the following order of occurrence: 1) carnivores, 2) carnivore/detritivores, 3) detritivores, 4) detritivore/herbivores, 5) herbivores, 6) herbivore/carnivores, and 7) herbivore/detritivores. Carnivores (64.1%) and carnivore/detritivores (13.6%) accounted for 77.7% of the total insects; these consisted of odonates, dytiscids, and notonectids (58.1%), with gerrids, belostomatids, nepids, and naucorids, comprising an additional 19%. The near uniform distribution of trophic level proportion rankings found among pools regardless of surrounding habitat was independent of pool size and longevity and indicated baseline similarity. Although ephemeral pools are known for being transitory, with respect to trophic levels, they may be more ecologically stable than is implied by their name. © 2003, Copyright Taylor & Francis Group, LLC.