GENETIC-VARIATION IN RELATION TO DEMOGRAPHY OF PERIPHERAL POOL FROG POPULATIONS (RANA-LESSONAE)

Genetic variation in an isolated northern metapopulation of the pool frog (Rana lessonae) in Sweden was compared to that of Central European populations using enzyme electrophoresis and literature data. Of the 31 loci scored, two (EST-2 and IDH-2) were polymorphic while no variation occurred in seven of the eight loci which are polymorphic in Central European populations. The heterozygosity level of the Swedish pool frogs (H(t)BAR = 0.002, H(s)BAR less-than-or-equal-to 0.0047) is very low compared to that of other anuran populations, but their mean proportion of fertilized eggs within egg masses (97.5%) was not lower than in more heterozygous species, and their body size-specific fecundity did not differ from that of Polish conspecifics. The low genetic variability of the Swedish pool frogs is discussed in relation to features of the local populations such as size (N), calculated effective size (N(e)), reproductive success and probable history. It is concluded that long-term strong fluctuations in population size caused by reproductive failure in cold years have contributed more to the low genetic variability than could a single founder event due to a recent introduction by man.