A Comparative Study of Two Corbicula Morphs (Bivalvia, Corbiculidae) Inhabiting River Danube

In Europe, at least two Corbicula morphs (generally referred as C. fluminea and C. fluminalis) are known. However, their taxonomic and systematic position is controversial. In order to ascertain their taxonomy and systematics, we studied their characteristics in River Danube. Morphometric analysis confirmed the existence of two distinguishable morphs. Based on mtCOI sequence, morph-1 is identical to C. fluminea, while morph-2 is an undefined species. According to the median joining analysis, morph-1 belongs to the C. fluminea clade, whereas morph-2 forms a distinct clade, which is known only from invasive populations. Differences were recorded in population structure and reproductive biology, too. It is probably correct to treat the two morphs as distinct taxa, but as long as the African and western Asian parts of the genus' range are poorly studied, taxonomic position of morph-2 remains unclear.