High genetic distance between marine bivalves of the genus mesodesma inhabiting the Atlantic and Pacific coasts of South America

Abstract

Molluscs of the genus Mesodesma are marine bivalves inhabiting the middle littoral on sandy beaches of temperate and subtropical systems, where they usually are the dominant organisms. This genus is represented on South America’s Atlantic coast by Mesodesma mactroides, and by Mesodesma donacium on the Pacific coast. Samples of these species from Brazil and Chile were compared genetically by electrophoresis at 26 isozyme loci. Out of 17 monomorphic loci, 14 were fixed for different alleles. Nine polymorphic loci were found; where 44 alleles were detected, 35 of these were distinct between both species. The statistical analysis showed a Nei’s genetic distance of 1.90. The high genetic distance observed here corroborates the controversy about mesodesmatid systematic problems.