Isolation by distance and low connectivity in the peppery furrow shell Scrobicularia plana (Bivalvia)

Abstract

Scrobicularia plana da Costa, 1778, a commercially important bivalve species in southern Europe, is commonly found along the NE Atlantic and Mediterranean coasts. Like other intertidal mollusk species, it has a wide distributional range and high potential for larval dispersal. However, S. plana has a patchier distribution than most co-distributed soft sediment bivalves of the intertidal, which could lead to lower interpopulation connectivity and stronger population structure. We surveyed 18 locations from throughout the species' range to determine overall population structure, phylogeographic distribution and historical demography. We sequenced a portion of the mitochondrial cytochrome-c-oxidase I gene (COI) for 423 individuals. Three population clusters (Trondheim, Atlantic and Pisa) were identified on the basis of pairwise F ST s. Demographic parameters were analysed in a coalescence framework. Strong differentiation was found between most Atlantic locations and the single Mediterranean location (Pisa). Among Atlantic locations, differentiation was weak and non-significant, though significant isolation-by-distance was detected. A star-shaped phylogeny with mostly 1-step mutations was found. Although 65 haplotypes were detected, 50 were private. The higher diversity observed in southern Europe, Brittany and Norway was consistent with glacial refugia. Population expansion occurred recently with the oldest split, which was between all Atlantic groups and the Mediterranean group, taking place 0.3 to 1.1 million years ago (Myr). Negative values for neutrality tests and the star-shaped haplotype network were also indicative of recent population expansion, although such a pattern can also be the result of a selective sweep. An isolation-by-distance effect and absence of migration reveal low interpopulation connectivity, which is likely reinforced by the species' patchy spatial distribution.KEY WORDS: Scrobicularia plana · Mitochondrial DNA · Genetic structure · Phylogeography · Glacial refugiaResale or republication not permitted without written consent of the publisher

Strong population structure but no equilibrium yet: Genetic connectivity and phylogeography in the kelp Saccharina latissima (Laminariales, Phaeophyta)

“…However, the comparison between the samples from Brittany and the Faroe Islands (Table A) provides an estimate of 174,000 years ago for the oldest population divergence among extant European S. latissima . This estimate is consistent with population expansion in Europe dating back to the ice ages of the Pleistocene and survival in northern refugia during the LGM (Last Glacial Maximum) and congruent with knowledge on postglacial recolonization of European Atlantic coasts (Maggs et al., ; Santos, Cruzeiro, Olsen, van der Veer, & Luttikhuizen, ). We suggest that haplotypes a, b, d, and e (Figure ) are ancestral in Europe (being the closest relatives of the Pacific haplotypes) and have given rise to the outer Atlantic haplotypes g and r 100 to 200 thousand years ago.…”

Patterns of genetic variation across the distribution range of the cockle Cerastoderma edule inferred from microsatellites and mitochondrial DNA

“…Nevertheless, evidence inconsistent with this theory suggests an alternative scenario where species could have survived in unknown or cryptic refugia at higher latitudes (Stewart and Lister 2001;Provan and Bennett 2008). The high levels of genetic diversity observed in some northern populations of Mytilus edulis (Riginos and Henzler 2008) and Scrobicularia plana (Santos et al 2012) as well as the population structure of Macoma balthica (Luttikhuizen et al 2003) support the existence of suitable local habitats within the area of glaciation.…”

Gene flow from multiple sources maintains high genetic diversity and stable population history of Common Moorhen Gallinula chloropus in China

“…The fact that the southern populations had generally higher genetic diversities than the northern ones, combined with the evidence of isolation‐by‐distance, suggests a likely ‘stepping‐stone’ dispersal (Santos et al . ) of Common Moorhen from the south to the north.…”