High macroinvertebrate richness and the influence of habitat diversity in the Edwards Plateau of central Texas

We assessed taxonomic richness and diversity of invertebrates in an Edwards Plateau stream (central Texas) and found that richness was 50 – 100% higher than other Texas Southern Gulf Slope streams and may rank among the richest populations in North America.  Benthic and drift samples were collected seasonally for two years from mainstem, tributary, and seep sites.  Total taxa was 181, including 28 Ephemeroptera genera, 25 Trichoptera, and 32 Coleoptera.  Heterogeneous aquatic habitats and a moderately warm climate were primary factors in maintaining species diversity in the Blanco River watershed.  Seep-associated taxa and hyporheic species, such as the blind cave amphipod Stygobromus russeli, are supported by stable microhabitats in an otherwise highly variable watershed.  Diverse habitats and an intermittent flow regime might also limit strength of invasive invertebrates like the clam Corbicula fluminea.  Central Texas represents an ecotone where several biotic realms and provinces intersect.  Aquifer draw-down currently threatens seeps and the Blanco River’s natural flow regime.  Conservation of biotic diversity in southwestern intermittent streams and preservation of aquatic habitat diversity depends on maintaining the natural flow regime.