A riparian zone in southern Illinois as a potential dispersal corridor for reptiles and amphibians

We surveyed reptiles and amphibians in a core area (Wildcat Bluff/Heron Pond) and at four sites along the Cache River in southern Illinois, USA, to assess whether the existing riparian zone would serve as a dispersal corridor for these species. Only 14 of the 37 species found in the core area were detected at all sites along the river, and 17 species were not found at the three sites furthest downriver from the core area. In contrast to our expectations, wide (greater than or equal to 1000 m) areas of riparian habitat did not support greater numbers of species of reptiles and amphibians than narrow (less than or equal to 100 m) areas. Proximity to the core area and local habitat heterogeneity appeared to best explain species richness at the sites surveyed. Examination of the literature on habitat requirements for the species found in the core area suggested that lack of upland habitats and of fishless pools, along with regular inundation of remaining riparian habitat, inhibit many species from occurring consistently throughout the corridor. Our results demonstrate the importance of including specific natural history requirements in the design of corridors, rather than simply relying on easy-to-measure parameters such as corridor width, especially for species with low vagility. (C) 1998 Elsevier Science Ltd. All rights reserved.