High dispersal in a frog species suggests that it is vulnerable to habitat fragmentation

W. Chris Funk, Allison E Greene, Paul Stephen Corn, Fred W Allendorf

Global losses of amphibian populations are a major conservation concern and their causes have generated substantial debate. Habitat fragmentation is considered one important cause of amphibian decline. However, if fragmentation is to be invoked as a mechanism of amphibian decline, it must first be established that dispersal is prevalent among contiguous amphibian populations using formal movement estimators. In contrast, if dispersal is naturally low in amphibians, fragmentation can be disregarded as a cause of amphibian declines and conservation efforts can be focused elsewhere. We examined dispersal rates in Columbia spotted frogs (Rana luteiventris) using capture-recapture analysis of over 10,000 frogs in combination with genetic analysis of microsatellite loci in replicate basins. We found that frogs had exceptionally high juvenile dispersal rates (up to 62% annually) over long distances (>5km), large elevation gains (>750m) and steep inclines (36 degrees incline over 2km) that were corroborated by genetic data showing high gene flow. These findings show that dispersal is an important life-history feature of some amphibians and suggest that habitat fragmentation is a serious threat to amphibian persistence.