Ecology of Heard Island Diptera
Résumé
Phenology, distribution and abundance of three Diptera species on Heard Island were investigated to provide baseline data for monitoring the eVect on climate change on populations. Five vegetation types at two localities were sampled in two diVerent years, Wrstly in the summer of 1987-1988 at Atlas Cove and secondly at Spit Bay over 12 months from summer 1992 to summer 1993. Pitfall traps and soil core extractions were operated in summer at both localities and pitfalls alone for 12 months from Spit Bay. The wingless Anatalanta aptera was the most abundant species in traps at Atlas Cove with most individuals collected from Poa tussock grassland, half as many from Pringlea and Azorella vegetation and fewest with a signiWcantly higher level of asymmetry in the large katepisternal setae, from Azorella and FellWeld. Calycopteryx moseleyi was the most abundant Xy in traps at Spit Bay, and A. maritima was the least abundant at both localities. Monthly pitfall catches from 1992-1993 indicated that A. aptera was active in most months of the year apart from winter, females early in the season and males active throughout the summer; teneral individuals only detected in January. C. moseleyi was more strongly seasonal with peak adult numbers occurring in January. Amalopteryx maritima was least seasonal in activity. Asymmetry in A. aptera suggests that it was at the limit of its ecological tolerance in FellWeld and Azorella on Heard Island. Changes caused by climate warming or invasive species are mooted.