Reticulate evolution, introgressive hybridisation, and phenotypic plasticity have been documented in scleractinian corals and have challenged our ability to interpret speciation processes. Stylophora is a key model system in coral biology and physiology, but genetic analyses have revealed that cryptic lineages concealed by morphological stasis exist in the Stylophora pistillata species complex. The Red Sea represents a hotspot for Stylophora biodiversity with six morphospecies described, two of which are regionally endemic. We investigated Stylophora species boundaries from the Red Sea and the associated Symbiodinium by sequencing seven DNA loci. Stylophora morphospecies from the Red Sea were not resolved based on mitochondrial phylogenies and showed nuclear allele sharing. Low genetic differentiation, weak isolation, and strong gene flow were found among morphospecies although no signals of genetic recombination were evident among them. Stylophora mamillata harboured Symbiodinium clade C whereas the other two Stylophora morphospecies hosted either Symbiodinium clade A or C. These evolutionary patterns suggest that either gene exchange occurs through reticulate evolution or that multiple ecomorphs of a phenotypically plastic species occur in the Red Sea. The recent origin of the lineage leading to the Red Sea Stylophora may indicate an ongoing speciation driven by environmental changes and incomplete lineage sorting.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): URF/1/1389-01-01, FCC/1/1973-07
Acknowledgements: We wish to thank the captain and crew of the MV Dream-Master, AK Gusti (KAUST), and the KAUST Coastal and Marine Resources Core Lab for fieldwork logistics in the Red Sea. Grazie to Tane H Sinclair-Taylor (KAUST) for graphic assistance. RA and TIT gratefully acknowledge P Saenz-Agudelo (UACH) and JD DiBattista (CURTIN) for their first assistance at KAUST. WE thank the two anonymous reviewers for their comments to earlier versions of the manuscript. This project was supported by funding from KAUST (award # URF/1/1389-01-01, FCC/1/1973-07, and baseline research funds to ML Berumen). This research was undertaken in accordance with the policies and procedures of the King Abdullah University of Science and Technology (KAUST). Permissions relevant for KAUST to undertake the research have been obtained from the applicable governmental agencies in the Kingdom of Saudi Arabia.