Impact of Geographical Isolation on Genetic Differentiation In An Insular Population of the Carpet Shell Ruditapes decussatus in the Mediterranean Basin

ABSTRACT Genetic variation was investigated using allozymes, cytochrome c oxidase subunit I, internal transcribed spacer region 1, and microsatellite markers in mainland and insular populations of the carpet shell Ruditapes decussatus from the western and eastern Mediterranean Basin. Five morphometric parameters and weight of valves were also used to study the distribution of variation within and among populations. The species is characterized by a relatively high inter- and intrapopulation morphological and genetic variability. The highest values of percent polymorphism and heterozygosity (allozyme and microsatellite data) were found in the sample from Kerkennah Island. The occurrence of higher levels of genetic variability in insular population is probably because this population inhabit marginal environment characterized by temporal-ecological instability. The genetic heterogeneity analysis demonstrates a certain amount of genetic differentiation among local populations of R. decussatus with a relative...