Phylogeography of the sergeants Abudefduf sexfasciatus and A. vaigiensis reveals complex introgression patterns between two widespread and sympatric Indo-West Pacific reef fishes.
On evolutionary timescales, sea level oscillations lead to recurrent spatio-temporal variation in species distribution and population connectivity. In this situation, applying classical concepts of biogeography is challenging yet necessary to understand the mechanisms underlying biodiversity in highly diverse marine ecosystems such as coral reefs. We aimed at studying the outcomes of such complex biogeographic dynamics on reproductive isolation by sampling populations across a wide spatial range of a species-rich fish genus: the sergeants (Pomacentridae: Abudefduf). We generated a mutlilocus data set that included ten morpho-species from 32 Indo-West Pacific localities. We observed a pattern of mito-nuclear discordance in two common and widely distributed species: Abudefduf sexfasciatus and Abudefduf vaigiensis. The results showed three regional sublineages (Indian Ocean, Coral Triangle region, western Pacific) in A. sexfasciatus (0.6-1.5% divergence at cytb). The other species, A. vaigiensis, is polyphyletic and consists of three distinct genetic lineages (A, B and C) (9% divergence at cytb) whose geographic ranges overlap. Although A. vaigiensis A and A. sexfasciatus were found to be distinct based on nuclear information, A. vaigiensis A was found to be nested within A. sexfasciatus in the mitochondrial gene tree. A. sexfasciatus from the Coral Triangle region and A. vaigiensis A were not differentiated from each other at the mitochondrial locus. We then used coalescent-based simulation to characterize a spatially widespread but weak gene flow between the two species. We showed that these fishes are good candidates to investigate the evolutionary complexity of the discrepancies between phenotypic and genetic similarity in closely related species.
Institute of Oceanography, National Taiwan University, N°1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan.
Joris A M
http://orcid.org/0000-0002-3379-1019
JAM
Bertrand
Institut de recherche pour le développement, UMR 250 'Ecologie marine tropicale des océans Pacifique et Indien', 101 promenade Roger-Laroque Anse Vata, BP A5, 98848 Nouméa cedex, New Caledonia.
Philippe
http://orcid.org/0000-0001-9469-8304
P
Borsa
Institute of Oceanography, National Taiwan University, N°1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan.
Wei-Jen
http://orcid.org/0000-0003-4751-7632
WJ
Chen
D000818:Animals; D004272:DNA, Mitochondrial / Q000235:genetics; D005399:Fishes / Q000145:classification*; D051456:Gene Flow; D006824:Hybridization, Genetic; D019156:Indian Ocean; D010140:Pacific Ocean; D010802:Phylogeny; D058974:Phylogeography
D004272:DNA, Mitochondrial
Pomacentridae; coral reef; cryptic lineage; interspecific gene flow; mito-nuclear discordance; multilocus phylogeny