Parallel pattern of differentiation at a genomic island shared between clinal and mosaic hybrid zones in a complex of cryptic seahorse lineages

Abstract

33Diverging semi-isolated lineages either meet in narrow clinal hybrid zones, or have a 34 mosaic distribution associated with environmental variation. Intrinsic reproductive 35 isolation is often emphasized in the former and local adaptation in the latter, although 36 both can contribute to isolation. Rarely these two patterns of spatial distribution are 37 reported in the same study system, while this could provide fundamental information on 38 the endless debate about the relative contribution of intrinsic reproductive isolation and 39 local adaptation on the speciation process. Here we report that the low diversity long-40 snouted seahorse Hippocampus guttulatus is genetically subdivided into five cryptic 41 semi-isolated lineages. Along the Atlantic coasts, northern and southern lineages meet 42 and coexist with little hybridization in the southwest of France, forming a clinal hybrid 43 zone. In the Mediterranean Sea, two lineages have a mosaic distribution associated with 44 lagoon-like and marine habitats. A fifth lineage was identified in the Black Sea. Genetic 45 homogeneity over large spatial scales within each lineage, together with among-locus 46 . CC-BY-NC-ND 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint (which . http://dx.doi.org/10.1101/161786 doi: bioRxiv preprint first posted online Jul. 10, 2017;. CC-BY-NC-ND4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint (which . http://dx.doi.org/10.1101/161786 doi: bioRxiv preprint first posted online Jul. 10, 2017;. CC-BY-NC-ND 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint (which . http://dx.doi.org/10.1101/161786 doi: bioRxiv preprint first posted online Jul. 10, 2017;. CC-BY-NC-ND 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint (which . http://dx.doi.org/10.1101/161786 doi: bioRxiv preprint first posted online Jul. 10, 2017;. CC-BY-NC-ND 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint (which . http://dx.doi.org/10.1101/161786 doi: bioRxiv preprint first posted online Jul. 10, 2017; variance in differentiation levels between lineages and spatial patterns of introgression 47 provide evidence that partial reproductive isolation is maintaining the divergence.