Opening the black box of the invasion of Corbicula clams (Bivalvia, Corbiculidae) in South America: a genetic and morphological evaluation

Among species of Corbicula , only the hermaphroditic androgenetic lineages are invasive while sexual species are restricted to the native range (mainly Asia). Four androgenetic lineages of Corbicula spp. have been identified in American and European freshwater systems, with the Corbicula sp. form A/R lineage being abundant on both continents. This lineage is considered an important invasive species because of its impact on aquatic ecosystems and industrial cooling systems. The present study identified the invasive lineages of Corbicula spp. in freshwater environments of South America based on morphometric data and used genetic marker (mtDNA COI gene) to investigate their genetic relatedness to the invasive lineages from Europe and North America. Four important results arise: (1) there are two invasive lineages of Corbicula in South America, Corbicula sp. form C/S and Corbicula sp. form A/R, and they are clonally expanding their distribution in continental aquatic systems of South America; (2) populations with intermediate morphotype were detected in three distinct sites of Brazil; (3) one population with individuals presenting a new COI haplotype was recovered with an intermediate morphotype; (4) the morphotype of the invasive lineages of Corbicula spp. in South America presents high correlation with their COI haplotypes.