Antarctic diptera: ecology, physiology and distribution

In contrast to northern polar areas, the dipteran fauna of Antarctica is depauperate, with only two naturally occurring species of Chironomidae. Surprisingly little is known of the biology of these species. One, Parochlus steinenii, reaches the southern limit of a distribution covering the high Andes, Tierra del Fuego, South Georgia and the South Shetland Islands in the maritime Antarctic. The other, Belgica antarctica, is endemic to the maritime Antarctic. What factors influence the distribution and past colonisation of these two species in the Antarctic? Distributional data and evidence from an accidental introduction of a third chironomid (Eretmoptera murphyi) suggest that difficulty of colonisation is the major factor limiting the number of dipteran species present in the maritime Antarctic. Other sub-Antarctic species are likely to be preadapted to more rigorous conditions, should natural or man-induced colonisation opportunities occur. Evidence from physiological and ecological studies identify adaptations which allow these two species to survive in the harsh terrestrial environment of Antarctica. Life history characteristics of all three species include flexibility in development rates and size achieved, and the ability to continue activity at low positive temperatures. The distribution of the endemic B. antarctica is probably limited by the availability of suitable moist, vegetated, habitats and its brachyptery, rather than biological constraints directly, whereas the southern distribution of P. steinenii may be temperature-limited. Competition does not appear to be an important factor in the biology and ecology of either species, or in Antarctic terrestrial ecosystems generally