Mitonuclear genetic patterns of divergence in the marbled crab, Pachygrapsus marmoratus (Fabricius, 1787) along the Turkish seas

Abstract

Biogeographical transition zones present good opportunities for studying the effect of the past ice ages on genetic structure of species because secondary contact zones of post-glacial lineages can be formed. In this study, we investigated the population genetic structure of the marbled rock crab, Pachygrapsus marmoratus along the coasts of Turkey. We genotyped 334 individuals from the Black Sea, the Turkish Straits System (TSS), the Aegean, and the Eastern Mediterranean basins. In order to reveal its evolutionary history and its population connectivity, we used mitochondrial CO1 region and five microsatellite loci. CO1 analyzes also included 610 additional samples from Genbank, which covered most of its distribution range. Both microsatellites and mtDNA showed decreased diversity in sampling sites of the TSS and the Black Sea as compared to those along the Aegean and the Levantine coasts. There is an especially strong geographical pattern in distributions of haplotypes in mtDNA, most probably as a result of genetic drift in the Black Sea and the Sea of Marmara (SoM). Microsatellite data analyses revealed two genetically distinct clusters of P. marmoratus (clusters C and M). While individuals belonging to cluster C are present in all the sampling locations, those belonging to cluster M are only detected along the Mediterranean coasts including the Aegean and the Levantine basins. These clusters shared similar haplotypes in the Mediterranean. Haplotypes of two sympatric clusters could be similar due to incomplete lineage sorting of ancestral polymorphisms. In order to retrieve the complex demographic history and to investigate evolutionary processes resulting in sympatric clusters in the Aegean Sea and the Levantine basin, mitochondrial markers with faster mutation rates than CO1 and/or SNP data will be useful.

Assessment of connectivity patterns of the marbled crab Pachygrapsus marmoratus in the Adriatic and Ionian seas through combination of genetic data and Lagrangian simulations

“…Previous genetic studies based on microsatellite polymorphisms (Fratini et al, 2008;Silva et al, 2009;Fratini et al, 2011;Fratini et al, 2013;Deli et al, 2016;Iannucci et al, 2020;Çetin et al, 2022) and mtDNA sequencing (Fratini et al, 2011;Kalkan et al, 2013;Deli et al, 2016;Fratini et al, 2016;Çetin et al, 2022) revealed weak but significant genetic heterogeneity among marbled crab populations in different areas including the Atlantic Ocean, the Black Sea and several Mediterranean Sea regions. In addition, former microsatellite studies, based on population samples separated by a few hundred kilometres, indicated that deviation from panmixia might occur at a small geographic scale, albeit the lack of geographically coherent differentiation suggests the existence of genetic patchiness.…”