THE EFFECTS OF VARYING SITE-WATER DURATION ON THE DISTRIBUTION OF WATER BEETLE ASSEMBLAGES, ADULTS AND LARVAE (COLEOPTERA, HALIPLIDAE DYTISCIDAE, HYDROPHILIDAE)

Seventy-seven ponds varying in site-water duration were sampled for beetles. Species assemblages were identified using TWINSPAN and the major trends in the variation were investigated using DECORANA. Site distribution in DECORANA ordination space indicated differences related to water duration. The distribution of the adults and larvae of water beetles species was related to varying site-water duration by logistic regression. A range of species preferences were identified. Some species preferred temporary water, some could not cope with any drying out and the optimum distribution of others varied between these two extremes. The results are discussed in relation to the concepts of seasonality and to the environmental stresses affecting the distribution of species. There appears to be scope for relating water beetle species distribution to climatic change.