High species richness of Chironomidae (Diptera) in temporary flooded wetlands associated with high species turn-over rates

Abstract

AbstractSpecies richness and species turn-over of Chironomidae was studied in irregularly flooded wetlands of the River Dalälven flood-plains in central Sweden. The chironomid fauna, sampled with emergence traps in six wetlands over six summers, contained as much as 135 species, and the cumulative species curves indicated that the regional species pool contain several more species. Recurrent irregular floods may have induced this high chironomid species richness and the high species turn-over in the temporary wetlands, as the dominance between terrestrial and aquatic species shifted between years. Half of the wetlands were treated withBacillus thuringiensisvar.israelensis(Bti) against larvae of the flood-water mosquitoAedes sticticus. These treatments had no significant effect on chironomid species richness, but there was a higher species turn-over between years of primarily low abundance species in the treated wetlands. The cumulative number of species was also higher in theBti-treated experimental wetlands than in the untreated reference wetlands. Thus,Btitreatment against mosquito larvae seemed to have only small effects on chironomid species richness but seemed to increase the colonisation-extinction dynamics.