Distinct biogeographic origins of androgenetic Corbicula lineages followed by genetic captures

Corbicula clams were introduced during the 20th century into America and Europe, where they became notoriously successful invaders with a widespread, global distribution. Their ability to reproduce clonally through androgenesis (all-male asexuality) has been determinant in their invasive success, with only four invasive clonal lineages detected across Europe and America, one of which is very abundant and widespread on both continents. Due to their all-male asexuality and egg parasitism between distinct lineages, the evolutionary and geographic origins of the invasive androgenetic lineages have been challenging to identify. We analyzed here the patterns of allele sharing for different molecular markers among Corbicula individuals collected worldwide. We identify three distinct genetic pools containing androgenetic Corbicula lineages. While one sexual Corbicula species forms a distinct fourth genetic pool, the other sexual lineages cluster with the androgenetic ones based on shared alleles. One genetic pool contains most androgenetic lineages and sexual C. sandai from Lake Biwa in Japan, pointing to this lake as a likely origin of androgenetic Corbicula lineages. Although three distinct biogeographic origins of Corbicula androgenetic lineages have been identified, their recent radiation and cross-lineage genetic mixing hamper classical species delimitation within this clam genus.