Local and regional macroinvertebrate diversity in the wetlands of a cleared agricultural landscape in south-western Victoria, Australia

Abstract

1. Seasonal pasture wetlands are a common freshwater habitat in many agricultural landscapes, but their invertebrate diversity has rarely been examined compared with other freshwater habitats. Few studies have examined the role of seasonal wetlands for regional biodiversity or the pattern of change in assemblage composition across landscapes. 2. Invertebrates were sampled from 16 naturally occurring seasonal wetlands and three perennial wetlands in south-western Victoria, Australia. The wetlands were arranged in three clusters, separated by at least 20 km: two clusters each contained one perennial and four seasonal wetlands surrounded by pasture; the remaining cluster consisted of one perennial wetland and four seasonal wetlands on a property that has not been cleared of native vegetation, and four adjacent seasonal pasture wetlands cleared of native vegetation. 3. Presence/absence data showed that seasonal wetlands had fewer taxa than perennial wetlands, but both were taxon rich. Turnover of taxa was high at all three scales, i.e. between samples within a wetland, between wetlands, and between wetland clusters, but each cluster did not have a characteristic assemblage composition. Up to two-thirds of the invertebrate taxa found in perennial wetlands were also found in seasonal wetlands, showing that seasonal pasture wetlands could provide an expanded area of winter–spring habitat for many taxa. 4. Seasonal pasture wetlands contribute to biodiversity in highly managed and depauperate agricultural landscapes. There was little regionalization of the fauna, taxon turnover was high and ranges appeared relatively continuous. Biodiversity in pasture wetlands was comparable to perennial non-pasture wetlands elsewhere, despite being used for grazing livestock. This suggests that pasture wetlands may have substantial conservation value and should be managed to protect them from threatening processes such as drainage. Copyright © 2005 John Wiley & Sons, Ltd.