PROC. ENTOMOL. SOC. WASH. 107(1), 2005, pp. 176-189 DIPTERA DIVERSITY IN A HOMOGENEOUS HABITAT: BRACHYCERA ASSOCIATED WITH SEDGE MEADOWS (CYPERACEAE: CAREX) IN QUEBEC, CANADA Frederic Beaulieu and Terry A. Wheeler Department of Natural Resource Sciences, McGill University, Macdonald Campus, Ste-Anne-de-Bellevue, Quebec, H9X 3V9 Canada (e-mail:
[email protected]) Abstract. — Species richness and community composition of Brachycera (Diptera) were compared in three sedge meadows dominated by two species of Carex (Cyperaceae) in the Lac St. Francois National Wildlife Area in southern Quebec, Canada. More than 10,000 specimens, representing 34 families and more than 338 species, were collected weekly from May to October 1999 by sweeping and yellow pan traps. Species richness was highest in Dolichopodidae, Chloropidae, Sciomyzidae, Syrphidae, Sphaeroceridae, and Ephydridae. The same families, along with Phoridae, Chamaemyiidae, and Muscidae, were also the most abundant. Overall species composition differed between sites and was apparently influenced by the type of vegetation and substrate. Correspondence analysis showed that habitat associations of the 39 most dominant species differed between sites. The assemblages of Brachycera in the two Carex lacustris meadows were similar and richer in saprophagous species than in the Carex aquatilis meadow. This is partly due to greater exposure of mud substrate in the C. lacustris meadows. Key Words: Diptera, Brachycera, Nearctic, wetlands, Carex, biodiversity, habitat, ecol-ogy Emergent plant communities in wetlands are areas of high biological productivity and conservation significance (Scott 1995, Keiper et al. 2002). The sedge genus Carex L. (Cyperaceae) is widespread and diverse in such habitats and is especially dominant in littoral areas, peatlands and wet meadows of temperate regions (Kukkonen and Toi-vonen 1988). The aquatic Diptera fauna of temperate wetlands is also species-rich and abundant, mostly due to a few nematoceran families, especially Chironomidae (Wrubleski 1987, Batzer and Wissinger 1996). Fewer studies have examined semi-aquatic or terrestrial Diptera associated with emergent plants or the substrate, although some (e.g., Davis and Gray 1966, Cameron 1972, Pollet 1992, Blades and Marshall 1994, Keiper et al. 2002, Foote 2004) have found high Dip-tera diversity in marshes and peatlands. Although their ecological roles are not well-studied, it is increasingly apparent that Diptera are a critical component in food webs and nutrient cycling and are an under-appreciated study group in conservation bi-ology (Haslett 2001, Keiper et al. 2002). Unfortunately, the use of Diptera as model organisms in community ecology and con-servation biology is hampered by a lack of baseline knowledge on their diversity and ecology in many habitats, including fresh-water wetlands. Despite the dominance of Carex and Diptera in wetlands, there has been rela-tively little study of their association. Most
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