Genic differentiation of Gerris odontogaster populations

Abstract

Enzyme gene variation was studied in 11 Gerris odontogaster (Zett.) (Heteroptera) populations from southern and Central Finland. The study was undertaken to compare genic variation and population differentiation of G. odontogaster to those of G. lacustris, studied earlier. Mean heterozygosity was lower in G. odontogaster than in G. lacustris. This could result from G. odontogaster populations being liable to strong sampling processes through frequent local extinctions and recolonizations of the populations, as the species favours semipermanent and temporary water bodies, whereas G. lacustris prefers more stable habitats. G. odontogaster populations were much more similar to each other than G. lacustris populations, which apparently results from more powerful dispersion. Contrary to G. lacustris, no geographic differences in the degree of population differentiation were observed, and the analysis of genetic distances did not reveal any geographical groupings of populations. The analysis of allele frequency variation among the populations simultaneously at all polymorphic loci studied showed that this variation is not statistically significantly different at the loci. This indicates that non-selective forces are sufficient explanations for the overall pattern of variation.