Radiation with reproductive isolation in the near-absence of phylogenetic signal
Martin Helmkampf, Floriane Coulmance, Melanie J. Heckwolf, Arturo Acero P., Alice Balard, Iliana Bista, Omár Domínguez‐Domínguez, Paul B. Frandsen, Montserrat Torres-Oliva, Aintzane Santaquiteria, José Tavera, Benjamin C. Victor, D. Ross Robertson, Ricardo Betancur‐R, W. Owen McMillan, Oscar Puebla
Abstract
According to the genic view, species are characterized by the genes that underlie functional divergence. Here, we take a phylogenomic approach to assess this view at the scale of a whole radiation. The hamlets ( Hypoplectrus spp.) represent a recent radiation of reef fishes from the Greater Caribbean that are reproductively isolated through assortative mating. A total of 335 genomes from 15 locations revealed a single well-supported phylogenetic split among species, with a large share of the radiation unresolved. The polytomic nature of the hamlet radiation is extreme compared to other recent radiations such as Lake Victoria cichlids. At the gene-tree level, we identified just one genomic region, centered around the casz1 transcription factor, with a topology that reflects species differences. These results show that phenotypic diversification and reproductive isolation—two major attributes of species—may unfold in the near-absence of phylogenetic signal, both genome-wide and at the gene-tree level.