Population genomics of local adaptation versus speciation in coral reef fishes (Hypoplectrus spp, Serranidae).
Are the population genomic patterns underlying local adaptation and the early stages of speciation similar? Addressing this question requires a system in which (i) local adaptation and the early stages of speciation can be clearly identified and distinguished, (ii) the amount of genetic divergence driven by the two processes is similar, and (iii) comparisons can be repeated both taxonomically (for local adaptation) and geographically (for speciation). Here, we report just such a situation in the hamlets (Hypoplectrus spp), brightly colored reef fishes from the wider Caribbean. Close to 100,000 SNPs genotyped in 126 individuals from three sympatric species sampled in three repeated populations provide genome-wide levels of divergence that are comparable among allopatric populations (F st estimate = 0.0042) and sympatric species (F st estimate = 0.0038). Population genetic, clustering, and phylogenetic analyses reveal very similar patterns for local adaptation and speciation, with a large fraction of the genome undifferentiated (F st estimate ≈ 0), a very small proportion of F st outlier loci (0.05-0.07%), and remarkably few repeated outliers (1-3). Nevertheless, different loci appear to be involved in the two processes in Hypoplectrus, with only 7% of the most differentiated SNPs and outliers shared between populations and species comparisons. In particular, a tropomyosin (Tpm4) and a previously identified hox (HoxCa) locus emerge as candidate loci (repeated outliers) for local adaptation and speciation, respectively. We conclude that marine populations may be locally adapted notwithstanding shallow levels of genetic divergence, and that from a population genomic perspective, this process does not appear to differ fundamentally from the early stages of speciation.
Evolutionary Ecology of Marine Fishes GEOMAR Helmholtz Centre for Ocean Research Kiel Düsternbrooker Weg 2024105 Kiel Germany; Faculty of Mathematics and Natural Sciences University of Kiel Christian-Albrechts-Platz 424118 Kiel Germany.
Sophie
S
Picq
Smithsonian Tropical Research Institute Apartado Postal 0843-03092 Panamá República de Panamá
W Owen
WO
McMillan
Evolutionary Ecology of Marine Fishes GEOMAR Helmholtz Centre for Ocean Research Kiel Düsternbrooker Weg 2024105 Kiel Germany; Faculty of Mathematics and Natural Sciences University of Kiel Christian-Albrechts-Platz 424118 Kiel Germany; Smithsonian Tropical Research Institute Apartado Postal 0843-03092 Panamá República de Panamá
Oscar
O
Puebla
Fish; RAD sequencing; local adaptation; marine; speciation