Vastrade M., Etoundi E., Bournonville T., Colinet M., Debortoli N., Hedtke S.M., Nicolas E., Pigneur L.-M., Virgo J., Flot J.-F., Marescaux J. and Van Doninck K.Please use the format "First name initials family name" as in "Marie S. Curie, Niels H. D. Bohr, Albert Einstein, John R. R. Tolkien, Donna T. Strickland"
<p style="text-align: justify;">“Occasional” sexuality occurs when a species combines clonal reproduction and genetic mixing. This strategy is predicted to combine the advantages of both asexuality and sexuality, but its actual consequences on the genetic diversity and species longevity are poorly understood. Androgenesis, a reproductive mode in which the offspring inherits its entire nuclear genome from the father, is often reported as a strictly clonal reproductive mode. Androgenesis is the predominant reproductive mode within the hermaphroditic, invasive lineages of the mollusk genus <em>Corbicula</em>. Their ability to reproduce clonally through androgenesis has been determinant in their invasive success, having colonized during the 20th century American and European freshwater systems, where they became notorious invaders with a widespread, global distribution. However, in androgenetic <em>Corbicula</em> clams, occasional genetic mixing between distinct lineages has also been observed when the sperm of one lineage fertilizes the oocyte of another one. Because of these occasional introgressions, the genetic relationships between <em>Corbicula</em> species remained unclear, and the biogeographic origins of the invasive androgenetic lineages have been challenging to identify. To address these issues, we analyzed the patterns of allele sharing for several nuclear and mitochondrial molecular markers among<em> Corbicula</em> individuals collected across both the native and invasive range. Our results show the occurrence of an allelic pool encompassing all <em>Corbicula</em> freshwater species worldwide, including sexual and androgenetic ones, which highlights the substantial genetic mixing within this genus. However, the differences in allele sharing patterns between invasive lineages, and the low diversity within each lineage, suggest recent, distinct biogeographic origins of invasive <em>Corbicula</em> androgenetic lineages. Finally, the polyploidy, high heterozygosity, and hybrid phenotypes and genotypes found in our study probably originated from hybridization events following egg parasitism between distinct <em>Corbicula</em> lineages. This extensive cross-lineage mixing found in <em>Corbicula</em> may generate nuclear diversity in an otherwise asexually reproducing species. </p>
androgenesis, asexuality, hybridization, invasion, allele sharing
