Broad-ranging low genetic diversity among populations of the yellow finger marsh crab Sesarma rectum Randall, 1840 (Sesarmidae) revealed by DNA barcode

Abstract

Population genetic studies on marine taxa, specifically in the field of phylogeography, have revealed distinct levels of genetic differentiation in widely distributed species, even though they present long planktonic larval development. A set of factors have been identified as acting on gene flow between marine populations, including physical or physiological barriers, isolation by distance, larval behaviour, and geological and demographic events. In this way, the aim of this study was to analyse the genetic variability among populations of the crab speciesSesarma rectumRandall, 1840 along the western Atlantic in order to check the levels of genetic diversity and differentiation among populations. To achieve this purpose, mtDNA cytochrome-coxidase subunit I (COI) (DNA-barcode marker) data were used to compute a haplotype network and a Bayesian analysis for genetic differentiation, to calculate an Analysis of Molecular Variance (AMOVA), and haplotype and nucleotide diversities. Neutrality tests (Tajima’sDand Fu’s ) were accessed, as well as pairwise mismatch distribution under the sudden expansion model. We found sharing of haplotypes among populations ofS. rectumalong its range of distribution and no significant indication for restricted gene flow between populations separately over 6000 km, supporting the hypothesis of a high dispersive capacity, and/or the absence of strong selective gradients along the distribution. Nevertheless, some results indicated population structure suggesting the presence of two genetic sources (i.e., groups or lineages), probably interpreted as a result of a very recent bottleneck effect due to habitat losses, followed by the beginning of a population expansion.