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Microhabitat and landscape influences on aquatic beetle assemblages in a cluster of temporary and permanent ponds

Aquatic beetles often have been regarded as mobile transients among water bodies, but recent studies suggest strong environmental influences on distribution and thus the potential for using beetles as bioindicators of habitat quality. We related aquatic beetle assemblage structure to environmental characteristics at 9 sites within a 0.5-km2 landscape in northern Delaware, USA. We sampled 6 temporary ponds (3 closed-canopy sites with short hydroperiods and 3 open-canopy sites with longer hydroperiods) and 3 permanent pond sites within a beaver pond. To evaluate microhabitats within ponds, we collected 6 shoreline and 6 deepwater samples at each site in early and late spring 2000 (n = 216), and classified samples according to 1 of 4 substrate types (dead leaves, Sphagnum, herbaceous vascular vegetation, and other substrate). Of the 46 species present in the samples, 5 were more abundant in temporary ponds, whereas 8 were more abundant at permanent sites. Similarly, 6 of 22 genera of larvae were more abundant in temporary ponds, whereas 7 were more abundant at permanent sites. We observed strong microhabitat affinities, with ∼85% of all individuals found along pond margins and ∼40% of all taxa associated with particular substrate types. Rates of species accrual relative to the number of individuals sampled increased late in the spring season, reflecting in part the timing of dispersal among ponds.