Allozyme variation as a demographic predictor at high latitudes: the moor frog and the pool frog at 60 degrees N

Allozyme variability was examined in relation to population size among sympatric moor frogs (Rana arvalis) and pool frogs (R. lessonae) at a pond in east-central Sweden (60 degrees N). Average heterozygosity (H) and polymorphism level (P), respectively, were 0.099 and 0.33 in the moor frog (24 loci) and 0.0047 and 0.071 in the pool frog (28 loci). This marked difference in variability corresponded to a significant difference in the yearly numbers of reproducing individuals corrected for skewed sex ratio, during a 5-yr. period preceding the genetic surveys. The mean of the moor frog population (64.6) exceeded that of the pool frogs (27.6), but the yearly deviation in relation to the mean did not differ between the species. The pool frogs in question belong to a geographically restricted metapopulation, while the moor frog is common and widespread in Scandinavia. Our results conform to the expectation that level of genetic diversity primarily reflect population characteristics such as size and gene flow even at this northern latitude, while disagreeing with a proposed deterministic relationship between life-zone (latitude) and genetic diversity.