The bivalve molluscMactra corallina: genetic evidence of existing sibling species

Abstract

The rayed trough-shellMactra corallinaLinnaeus 1758 is a surf clam that inhabits the Atlantic Ocean, Black Sea and Mediterranean Sea and represents a commercially important bivalve. This species is present with two different and well-defined sympatric morphotypes, which differ mainly for the colour of the shell (white in thecorallinamorph, and brown-banded in thelignariamorph). The aim of this work is to resolve the confused and contradictory systematics of the bivalves belonging toM. corallinaputative species by analysing molecular and morphological features. Fifteen specimens ofM. corallina corallina(white variant) and 19 specimens ofM. corallina lignaria(brown variant) were collected in the North Adriatic Sea and analysed by four molecular markers (12S, 16S, 18S and COI genes, partial sequences). Genetic analyses clearly support the presence of two different species, which were previously ascribed toM. corallina.In addition, 35 specimens identified on a morphological basis asM. c. corallinaand 28 specimens identified asM. c. lignariacollected in the same area were used for a morphometric analysis. A positive correlation was found between the maximum width of shell (W), antero-posterior length and between W and the height of specimens from umbo to ventral margin, thus adding to molecular data.