Habitat characteristics predict occupancy patterns of the endangered amphibian Litoria raniformis in flow-regulated flood plain wetlands

摘要

Identification of habitat features that are strongly associated with the occurrence of threatened species is important in terms of predicting impacts of habitat change and identifying key habitats for conservation. In this paper, we apply habitat-based statistical models to predict occupancy patterns of the endangered southern bell frog (Litoria raniformis) across inland New South Wales (Australia). Litoria raniformis previously occupied a wide range of natural and man-made waterbodies across a large geographic range, including flood plain wetlands, oxbow lagoons, irrigation canals and rice bays. Alteration of natural flooding regimes has affected a large proportion of habitats within the historical range of Litoria raniformis, but it is not clear how these changes have influenced habitat occupancy patterns. Fifty-two waterbodies were surveyed for presence/absence of Litoria raniformis in 2001 and 2004. Stepwise logistic regression models were generated to select a subset of variables that best predicted occupancy. Using three predictor variables, vacant and occupied habitats could be predicted with an accuracy of 90% and 70%, respectively. The predictor variables were: the interaction between wetland hydrology and complexity of aquatic vegetation, complexity of fringing vegetation and water temperature. While this study demonstrated that a range of waterbody types were occupied by Litoria raniformis, these habitats shared common hydrological conditions and vegetation characteristics. Altered flooding regimes and reductions in the complexity of aquatic and fringing vegetation are likely to increase the probability of localized extinctions of Litoria raniformis populations.