Habitat preference and reproductive traits in the Antarctic midge Parochlus steinenii (Diptera: Chironomidae)
We provide the first comprehensive account of habitat preference, mating, oviposition and developmental stages of Parochlus steinenii. There are eight records from the South Shetland Islands. On King George Island, none out of 40 temporary ponds and 9% out of 44 lakes with variable water levels were inhabited by P. steinenii. By contrast, 94% of 52 lakes with stable water levels were occupied, for 92% of which breeding was confirmed. Lakes were occupied independently of their height above sea level ranging from 5 to 115 m. The midges aggregated at two different microhabitats at the shoreline of lakes. Terrestrial swarms of more than 5000 individuals at open wind sheltered rocks were strongly dominated by males. Their mean density was 40, their maximum 150 ind. cm−2. Aggregations under stones at the water edge showed a female-biased or equal sex ratio; their densities seasonally increased from 0.17 to 2.02 ind. cm−2. Female midges produced one to four egg batches totalling on average 247 eggs/female. Four larval stages can be clearly discriminated by head length. Our data on the habitat preferences and the high reproductive output predict that P. steinenii will rapidly colonize habitats that become available in the course of the regional warming of the Antarctic Peninsula region.(Received June 3 2005)
(Accepted October 24 2005)
Key Words: climate change; freshwater; lake; Maritime Antarctic; population; sex ratio; swarm.
p1 current address: Department of Plant-Animal Interactions, Centre for Limnology, Netherlands Institute of Ecology (NIOO-KNAW), PO Box 1299, 3600 BG Maarssen, the Netherlands S.Hahn@nioo.knaw.nl