Reintroduction of a declining amphibian: Determining an ecologically feasible approach through analysis of decline factors, genetic variation, and habitat associations

Species reintroductions provide opportunities for integrating practical and theoretical aspects of conservation biology. Amphibians present challenges for reintroduction because of their biphasic life cycles, low mobility, and patchy distributions. This study focused on a California/Oregon stream-dwelling, declining amphibian, the foothill yellow-legged frog (Rana boylii), and included three components: (1) causes of decline, (2) genetic variation, and (3) habitat associations.  For decline analyses, the current status of R. boylii at historic localities was spatially related to:  topography, land use, wind-borne toxins, climatic variables, and proximity and size of dams.  Climatic variables were good predictors and there was evidence of interactions; especially that negative effects of dams were exacerbated in areas with low precipitation. For genetic analyses, sequences from two mtDNA fragments for individuals from 34 localities were used.  Phylogenetic analyses recovered well-supported, geographically congruent clades. Genetic variation was low among populations in the largest clade, but individuals from several localities showed substantial divergence.  Hydrologic regions, which represent likely dispersal corridors, explained local patterns of genetic variation.  Habitat associations analyses evaluated microhabitat scale oviposition site characteristics and larger scale patterns of occurrence and abundance at breeding areas.  The narrow range of oviposition microhabitat characteristics (e.g., water depth, water velocity, and stream substrate) relative to available habitats suggested selection.  I discuss the application of these results to amphibian reintroductions and propose a conceptual model for integrating this and other information into reintroduction programs. Combining pre-reintroduction research on ecology, genetics, and causes of declines with experimental reintroductions and rigorous monitoring should increase reintroduction success rates.