Feeding ecology of larval net-winged midges (Diptera: Blephariceridae: Blepharicera Macquart) from the southern Appalachian Mountains

Alverson, Andrew
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Ecology, Evolution, and Organismal Biology

Despite the widespread perception that the Blephariceridae (Diptera) are a rare and functionally homogenous family, a decade of collecting and surveying the southern Appalachian Mountains has revealed that the region has a diverse fauna consisting of 13 Blepharicera species; an unusually high degree of regional and local sympatry among congeneric species; and predictable patterns of spatial and phenological mechanisms of ecological isolation among congeners. I describe the feeding characteristics of 7 Blepharicera species distributed among 3 sites in southern Appalachia. The algal assemblage of larval diets was assessed to explore potential ecological isolation of congeners overlapping in space and time through partitioning of food resources and patterns of grazing efficiency among Blepharicera species. Data showed that larval blepharicerids are true scrapers that feed almost exclusively on diatoms, dietary differences among groups occupying different microhabitats, and differences in grazing efficiency among species. Eight Blepharicera species inhabit Cataloochee Creek, North Carolina. Based on season of larval activity, species can be broadly distinguished as winter, spring, or summer types. I examined fourth-instar diets of 2 temporally isolated species that have relatively long larval activity periods and a protracted fourth-instar stadium. Dietary assemblage structure, larval grazing efficiency, and total diatom consumption were measured for B. magna (winter type) and B. similans (summer type) to investigate whether larval grazing patterns changed over time. Data showed that algal assemblages in diet of B. magna did not vary over time. Algal assemblages in the diet of B. similans varied significantly throughout its fourth-instar stadium. Furthermore, total diatom consumption by both species was greatest at midstage, and both species showed consistently low larval grazing efficiency, due to positive differential ingestion of adnate and prostrate diatom species. I also present general information about blepharicerid biology, emphasizing their importance in the structure and function of lotic ecosystems.