Congruence between allozyme and RAPD data in assessing macrogeographical genetic variation in the periwinkle Littorina striata (Mollusca, Gastropoda)

The population genetic structure of the Macaronesian planktonic-developing periwinkle Littorina striata was analysed, using random amplified polymorph ic DNA analysis (RAPD). Two primers, yielding six polymorphic loci, were su rveyed to infer the population genetic structure of five geographically sep arated populations (i.e. 10-2000km). Biased and unbiased allele frequency a nd heterozygosity levels were estimated and were found to be highly similar . As in previous allozyme studies, our results suggest that populations of L. striata display (i) only little amounts of genetic heterogeneity and pop ulation differentiation, (ii) high levels of gene flow, between geographica lly separated populations and within a single population, between two disti nct shell morphs (i.e. nodulose and smooth shells) and (iii) a tendency for northern populations to be less heterozygous than southern populations. Th e current results reveal a high congruence between allozyme and RAPD data, suggesting that geographically separated populations and different shell mo rphs share a common gene pool. Given the fact that our RAPD loci might be c onsidered as neutral markers, we conclude that the previously analysed allo zymes were representative for L. striata's entire genome.