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Data from: The hidden side of a major marine biogeographic boundary: a wide mosaic hybrid zone at the Atlantic–Mediterranean divide reveals the complex interaction between natural and genetic barriers in mussels

Citation

El Ayari, Tahani et al. (2018), Data from: The hidden side of a major marine biogeographic boundary: a wide mosaic hybrid zone at the Atlantic–Mediterranean divide reveals the complex interaction between natural and genetic barriers in mussels, Dryad, Dataset, https://doi.org/10.5061/dryad.m3t6p5g

Abstract

The Almeria-Oran Front (AOF) is a recognised hotspot of genetic differentiation in the sea. It is a barrier to dispersal and an ecological boundary, which explain the position of genetic breaks. However, the maintenance of genetic differentiation is likely reinforced by genetic barriers. A general drawback of previous studies is an insufficient density of sampling sites at the transition zone with a conspicuous lack of samples from the southern coastline. We analysed the genetic structure in the mussel Mytilus galloprovincialis with ancestry-informative loci. We discovered a 600 km wide mosaic hybrid zone eastward of the AOF along the Algerian coasts. This mosaic zone provides a new twist to our understanding of the Atlantic-Mediterranean transition because it demonstrates the two lineages can live in sympatry but hardly interbreed. This implies some form of reproductive isolation must exist to maintain the two genetic backgrounds locally cohesive. The zone ends with an abrupt genetic shift at a barrier to dispersal in the Gulf of Bejaia. Simulations in models that account for hydrodynamic features of the region support the hypothesis that sister hybrid zones could have been differentially trapped at two alternative barriers to dispersal or environmental boundaries. A preponderantly unidirectional north-south gene flow next to the AOF can also maintain a patch of an intrinsically maintained genetic background in the south and the mosaic structure. Our results concur with the coupling hypothesis that suggests natural barriers mostly explain the position of genetic breaks while their maintenance must additionally require genetic barriers.

Usage Notes

Location

Medterranean area
Atlantic