Environmental Determinates of Stream Caddisfly (Trichoptera) Diversity in Eastern Texas, USA

Abstract

We assessed Trichoptera diversity for 91 wadeable stream sites in eastern Texas, and caddisflies were found at 86 sites. Caddisfly larvae were collected separately from benthic samples and from snag habitat (woody debris). We collected 13 families and 28 genera from benthic samples and 9 families and 21 genera of Trichoptera from snag habitats, and there was broad overlap among taxa between the two habitat types. A significantly greater number of genera were collected from non-urban benthic samples (mean=4.29, range=1–11) than urban ones (mean=2.6, range 1–7) (t-testα=0.05, t=3.57, P=0.0006) (Fig. 3A). We also found significantly fewer genera on snag habitats (mean=2.12) in urban streams compared to non-urban streams (mean=3.48) (t-testα=0.05, t=4.14, p=0.0001). We used correspondence analysis to evaluate data from benthic and snag habitats in nonurban and urban locations. Several genera were more commonly associated with urban streams while other genera were more commonly associated with non-urban streams. Finally, we used Canonical Correspondence Analysis to evaluate more than two dozen water quality and habitat variables as environmental determinates of caddisfly diversity and distribution, and this analysis showed that the distributional relationships among genera are complex and often a function of multiple environmental factors.