Nuclear DNA restriction site polymorphisms and the phylogeny and population structure of an intertidal snail species complex (Littorina)

Primers for amplification of four novel, unlinked nuclear DNA loci, the fir st reported for the rough periwinkles of the genus Littorina. are described . patterns of restriction site polymorphism for these loci are derailed wit hin the rough periwinkles. RFLPs are not found to be diagnostic for any of the currently accepted species within this group, nor for any of the conten tious subspecies, or forms, whose taxonomic status is uncertain. However, t here are important differences in allele frequencies between these taxa and certain of these mirror differences detected in a previous study of the mi tochondrial DNA. These allele frequency data are used to construct a phylog eny in which groupings of the three recognised species are obvious when eit her Nei's genetic distances or Reynolds distances are clustered. Contentiou s forms (L. neglecta, L. saxatilis 'b' and L. tenebrosa) do not cluster as distinct taxa, although populations of L. neglecta have important allele fr equency differences from L. saxatilis. These four loci have confirmed the c onsensus view of Littorina phylogeny and provided important information on population structure-however four loci is insufficient For reaching definit ive conclusions. Since analysis of nuclear DNA polymorphisms such as these is invaluable for analysis of phylogeny. population structure and phylogeog raphy, identification of additional loci is considered imperative.