Island biogeography of temporary wetland carabid beetle communities
The study tests if island biogeography is applicable to invertebrate communities of habitat islands in the agricultural landscape that are not fragments of formerly larger habitats. Location
Thirty temporary wetlands in the agricultural landscape of northeast Germany. Methods
The composition and species richness of carabid beetle communities was analysed. Habitat area, isolation, the density of temporary wetlands in the landscape, land-use intensity and the maximum duration of flooding were recorded as independent variables. Overall species richness and wetland species richness were studied in independent regression analyses. The community composition was analysed by means of a Canonical Correspondence Analysis (CCA). A partial CCA was used to analyse the effect of the distance to the edge of the field after removing impacts of other independent variables. Results
The area of the habitats and various measures of isolation (mean distances = 81–240 m) did not influence species richness or wetland species richness. The community composition was mainly determined by the land-use intensity, habitat area did not have significant effects, and the distance to the edge of the field was the only effective isolation parameter. Short-winged species were more often affected by the distance to the edge of the field than full-winged species. Main conclusion
There is evidence that the distances between the wetlands do not provide an effective barrier to the species dispersal and, therefore, metapopulation structures including subpopulations of multiple temporary wetlands might counteract local area effects on subpopulations. Short-winged species, however, might be more affected by isolation than full-winged species. As carabid beetle community structure in most early successional habitats is similar, these results may be representative of many agricultural landscape habitats. Nature conservancy concepts that aim to increase habitat area and habitat connectivity have successfully been applied to fragmented late-successional habitats. The present study indicates that such concepts do not necessarily result in higher diversity or larger populations in early successional habitats.