Distinct species hidden in the widely distributed coral Coelastrea aspera (Cnidaria, Anthozoa, Scleractinia)

Species identification is key for coral reef conservation and restoration. Recent coral molecular-morphological studies have indicated the existence of many cryptic species. Coelastrea aspera (Verrill, 1866) is a zooxanthellate scleractinian coral that is widely distributed in the Indo-Pacific. In Japan, this species is distributed from the subtropical reef region to the high-latitudinal non-reef region. Previous studies have reported that C. aspera colonies in the non-reef region release egg-sperm bundles (bundle type), whereas those in the reef region release eggs and sperm separately (non-bundle type) and release planula larvae after spawning. This difference in reproduction might be relevant to species differences. To clarify the species delimitation of C. aspera, the reproduction, morphology and molecular phylogeny of C. aspera samples collected from reef and non-reef regions in Japan were analysed, along with additional morphological and molecular data of samples from northern Taiwan. The results show that C. aspera is genetically and morphologically separated into two main groups. The first group is the non-bundle type, distributed only in reef regions, whereas the second group is the bundle type, widely distributed throughout the reef and non-reef regions. Examination of type specimens of the taxon’s synonyms leads us to conclude that the first group represents the true C. aspera, whereas the second is Coelastrea incrustans comb. nov., herein re-established, that was originally described as Goniastrea incrustans Duncan, 1886, and had been treated as a junior synonym of C. aspera.