Gene flow among populations of the leafbeetle species Gastrophysa polygoniand Lochmaea suturalis in Denmark (Coleoptera : Chrysomelidae)

The genetic differentiation of populations of the leaf beetles Gastrophysa polygoni Linnaeus 1758 and Lochmaea suturalis Thomson 1866 was measured by use of allozymes in order to estimate the gene now between geographically s eparated populations. 264 specimens of G polygoni from 4 Danish localities and 286 specimens oft suturalis from 3 Danish localities were analysed for 12 and 9 enzymes, respectively. 11 out of 17 loci from G polygoni were poly morphic and 8 out of 10 from L suturalis. No difference in the allelic dist ribution between sexes within each population of G polygoni was found. The level of heterozygosity was of the same magnitude for all seven populations studied. For each species a high genetic identity between the populations was found, but lack of homogeneity between allelic distributions of the pop ulations revealed local divergence. The estimated gene now corresponded to 3-4 reproducing individuals per generation for each species, which indicate s that genetic exchange between the populations does occur.