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(80-03) Local adaptation to polluted sediments by Chironomus februarius and its implications for the use of Fluctuating Asymmetry as a biomonitoring technique. Ward, Jacqueline*,1, Hoffmann, Ary2, 1 Centre for Environmental Stress and Adaptation Research, Bundoora, Victoria2 Centre for Environmetal Stress and Adaptation Research, Bundoora, Victoria ABSTRACT- The measurement of fluctuating asymmetry (FA) is a popular method of detecting and assessing human induced disturbances to freshwater ecosystems. It has been proposed that stressful environmental conditions may induce departures from perfect bilateral symmetry, with resulting elevations in FA providing an indirect measure of stress. Advocates of FA propose that this measure may provide an expedient, cheap and sensitive means of identifying natural populations threatened by induced stresses. However, results of studies using this method are inconsistent and further evaluation is required. There may be several reasons for inconsistencies, including genetically based adaptation by local species to pollutants. If an organism becomes adapted to pollutants, it may no longer be stressed, leading to lower than expected FA values. A field experiment using mesocosms was undertaken to investigate FA and local adaptation to heavy metal polluted urban sediments. Sediment was placed reciprocally at polluted and unpolluted wetlands. Chironomid larvae that colonised the mesocosms were allowed to eclose and adults were subsequently collected. Of the chironomid species that colonised the mesocosms, Keifferulus intertinctus and Chironomus februarius predominated. Life history data were recorded for each species. For FA analysis 28 wing traits were scored using landmark analysis and 2 thoratic bristle traits were measured for both species. Abundance and survivorship results suggest local adaptation to polluted sediments is likely for C. februarius but not for K. intertinctus. This provided an opportunity to evaluate the effects of both local adaptation and stress on FA and other measures of trait variability. Key words: urban, wetlands, heavy metals, trait variability |
