RAPD marker estimation of genetic structure among isolated northern leopard frog populations in the south-western USA.

Amphibians in the south-western United States are currently experiencing population declines. Causal explanations for these population changes as well as the implementation of sound management practices requires an understanding of the genetic structure of natural amphibian populations. To this end, we estimated genetic differences within and among seven isolated populations of northern leopard frogs, Rana pipiens, from Arizona and southern Utah using random amplified polymorphic DNA (RAPD) analyses. Fourteen arbitrarily designed primers detected 38 polymorphic loci in 85 individual frogs. Three types of population structure were observed in this study. (i) Two populations showed low genetic diversity (D = 0.10 and 0.04) and may have been established by relatively recent events. (ii) Two were not genetically distinct and exhibited a high degree of within-population diversity (D = 0.35). The possibility of gene flow between these populations is high due to their geographical proximity and their shared genetic structure. (iii) Three populations were genetically distinct from each other and the other populations, and exhibited intermediate within-population variation (D = 0.19, 0.17, 0.14). Genetic distances among the seven populations ranged from 0.00 to 0.20, suggesting that some of these leopard frog populations are genetically distinct. Although based on relatively small samples, these data suggest that leopard frog populations in the south-west are likely to represent unique genetic entities worthy of conservation. The management implications of these results are that isolated leopard frog populations should be evaluated on an individual basis to best preserve them.