Allozyme Variation and Population Genetic Structure in the Carpet Shell Clam Ruditapes decussatus Across the Siculo-Tunisian Strait

Abstract

This study reports on the polymorphism of 15 allozyme loci in Ruditapes decussatus clams collected from 11 locations along the Tunisian coasts. We concentrated our sampling effort around the Siculo-Tunisian region to verify if any population structuring exists in this region and to identify the factors that have shaped this structure. Measurements of genetic diversity were quantified both within and between populations, and the geographic variability of gene frequencies was analyzed. Our study shows that the Siculo-Tunisian Strait is an important genetic boundary between eastern and western regions, which agrees with findings for a variety of other species. We suggest that vicariance is a predominant factor shaping the current distribution of genetic diversity of R. decussatus, and the mixing of divergent gene pools from the eastern and western regions still seems to be limited by some physical and/or biological factors.

Concordant patterns of mtDNA and nuclear phylogeographic structure reveal Pleistocene vicariant event in the green crab Carcinus aestuarii across the Siculo-Tunisian Strait

“…This phylogeographical pattern, verified by both mitochondrial and nuclear markers, is interestingly in congruence with previous morphometric investigations of green crab populations from the same region, which showed strong morphometric differentiation between Eastern and Western Mediterranean populations (Deli et al, 2014). The concordance of genetic and phenotypic characters in defining two distinct groups of C. aestuarii suggests geographic separation, triggered by divergent selection pressures between alternative environments, and may hint at a possible signature of historical events that took place in the study region and might have shaped the genetic structure of many marine species, such as fishes (Bahri-Sfar et al, 2000;Mejri et al, 2009;Kaouèche et al, 2011), molluscs (Gharbi et al, 2011), and shrimps (Zitari-Chatti et al, 2008;. The striking similarity of biogeographic patterns reinforces the idea that these Mediterranean species were probably facing the same historical events and strongly suggests vicariance events during Pleistocene glacial episodes characterized by strong climate fluctuations (Thiede, 1978).…”

Phylogeography of the marbled crabPachygrapsus marmoratus(Decapoda, Grapsidae) along part of the African Mediterranean coast reveals genetic homogeneity across the Siculo-Tunisian Strait versus heterogeneity across the Gibraltar Strait

“…This study provides evidence for the absence of a significant genetic structure across the Siculo-Tunisian Strait, as inferred from mtDNA and nuclear microsatellite loci analyses. The Siculo-Tunisian Strait is considered as a well-documented genetic boundary between African Mediterranean populations of many marine species of fishes (Bahri-Sfar et al 2000;Mejri et al 2009;Kaouèche et al 2011), molluscs (Gharbi et al 2011) and shrimps (Zitari-Chatti et al 2009), but apparently does not seem to interrupt the connectivity among African populations of P. marmoratus from the Western and Eastern Mediterranean Basins. The lack of genetic structure could be explained by the passive dispersal of planktonic larvae, which could limit the formation of population substructure (Lessios et al 2003;Waters & Roy 2004).…”

Assessing the geographic scale of genetic population management with microsatellites and introns in the clam Ruditapes decussatus

“…To help designing restocking programs and managing strategies, there has been an interest in obtaining basic population genetic data. Several studies on the population genetics of R. decussatus have appeared along the last 25 years (Jarne et al 1988;Borsa et al 1991Borsa et al , 1994Jordaens et al 2000;Cordero et al 2008Cordero et al , 2014Gharbi et al 2010Gharbi et al , 2011Pereira et al 2011;Borrell et al 2014;Habtemariam et al 2015). However, only two studies have sampled a significant number of populations (Borsa et al 1994;Cordero et al 2014).…”