Unique issues of the species concept in molluscs of the genus Corbicula: a mismatch of mitochondrial and nuclear genomes

Abstract

Molluscs of the genus Corbicula are well-known invasive bivalves found all over the world. These ecologically important clams are characterised by a wide range of habitats (both brackish waters and freshwater environments) and by contrasting modes of reproduction in native ranges (including sexual and asexual modes) and in invasive ranges (asexual mode). The asexual freshwater Corbicula reproduces through androgenetic fertilization, also termed “egg parasitism”, where the oocyte nucleus is replaced by the spermatozoon nucleus, yet the mitochondria are inherited from the mother cell. This results in a mismatch between the genetic material of the nucleus and mitochondria (and, accordingly, with the external morphology of the shell). In addition, the low nucleotide diversity in the genus Corbicula challenges the delimitation of separate species, thus it is difficult to apply the traditional taxonomic and phylogenetic species criteria to Corbicula populations.