Abstract
Molecular and morphological data suggest that the Mediterranean populations of the non-indigenous genus Dendostrea are part of a single clade. This clade includes oysters from Rodrigues but is distinct from oysters from Hawaii and Mauritius. Based on morphology and sequence data, the Hawaiian and Mauritian oysters can be referred to as Dendostreasandvichensis Sowerby, 1871. The Mediterranean/Rodrigues clade, although morphologically very similar to D.sandvichensis, is significantly genetically distant from it and from D.frons and D.folium. As a result, the Mediterranean/Rodrigues clade cannot be assigned to any currently accepted nominal species. However, the statuses of the junior synonyms of D.sandvichensis are based on morphology and are therefore reconsidered with the result that D.crenulifera Sowerby, 1871 is shown to be morphologically very similar to the Mediterranean/Rodrigues clade. Given that the type locality of D.crenulifera is the Red Sea, and that Mediterranean populations are considered tropical invaders, D.crenulifera is a likely candidate name. However, without supporting sequence data from the type locality in the Red Sea, we conservatively conclude that the most appropriate name for the Mediterranean/Rodrigues clade is Dendostreacf.crenulifera (Sowerby, 1871).