Genetic differentiation among northern and southern populations of the moor frog Rana arvalis Nilsson in central Europe

Starch gel electrophoresis and morphometric characters were used to assess the geographical variation between 14 populations of the moor frog, Rana arvalis, from northern and southern areas in Central Europe. Six of the 13 screened allozyme loci were polymorphic (95% criterion). No fixed differences in allele composition between the two regions were found. Some of the alleles were region specific. Genetic variability as measured by expected heterozygosity ((H) over bar(e)) and number of alleles per locus was significantly lower in the southern samples than in northern ones ((H) over bar(e) = 0.104 and (H) over bar(e) = 0.156, alleles/locus = 1.6 and 1.8 respectively). This is interpreted as a consequence of the different past history of these two groups during the Pleistocene. Population subdivision, as measured by F-ST, was substantial (0.124 and 0.078 for the southern and northern group, respectively); 59.9% of the between-locality variation is attributed to this division into two geographical groups. Isolation-by-distance was detected by significant negative correlation between the estimate of gene flow (log (M) over cap) and log(geographical distance) only for the southern population groups. This indicates that the northern populations have recently recolonized their contemporary distribution area. The mean genetic distance between the northern and southern group of populations was D-N = 0.062. Despite the relatively low genetic distance between them, the two population groups form two distinct clusters in the maximum likelihood (ML) tree. Discriminant analysis on 11 size adjusted body measurements showed considerable overlap between populations from different geographical areas. An isolated Romanian Reci population which genetically belongs to the southern group of populations was morphologically situated in an intermediate position between northern and other southern populations.