Substantial genetic mixing among sexual and androgenetic lineages within the clam genus Corbicula

Abstract

18Corbicula clams were introduced during the 20 th century into America and Europe, where they became 19 notoriously successful invaders with a widespread, global distribution. Their ability to reproduce clonally through 20 androgenesis ("all-male asexuality") has been determinant in their invasive success, with only four invasive clonal 21 lineages detected across Europe and America, one of which is very abundant and widespread on both continents. 22Due to their "all-male asexuality" and egg parasitism between distinct lineages, the evolutionary and geographic 23 origins of the invasive androgenetic lineages have been challenging to identify. We analyzed here the patterns of 24 allele sharing for different molecular markers among Corbicula individuals collected worldwide. We identify three 25 distinct genetic pools containing androgenetic Corbicula lineages. While one sexual Corbicula species forms a 26 distinct fourth genetic pool, the other sexual lineages cluster with the androgenetic ones based on shared alleles. 27One genetic pool contains most androgenetic lineages and sexual C. sandai from Lake Biwa in Japan, pointing to 28 this lake as a likely origin of androgenetic Corbicula lineages. Although three distinct biogeographic origins of 29Corbicula androgenetic lineages have been identified, their recent radiation and cross-lineage genetic mixing 30 hamper classical species delimitation within this clam genus. 31 32

The Origin of the Subtropical Coral Alveopora japonica (Scleractinia: Acroporidae) in High-Latitude Environments

“…The haplotype network was inferred using HAPSTAR v0.7 (Teacher and Griffiths, 2011) to identify the phylogenetic relationships among haplotypes. A further analysis was conducted using Haplowebs (Flot et al, 2010;Etoundi et al, 2019) with the online tool HaplowebMaker 1 to show haplotype networks with additional connections between haplotypes found co-occurring in heterozygous individuals (Supplementary Figure S3). The genetic diversity indices of three separate clades (Korea, Taiwan, and Japan) were estimated using ARLEQUIN v3.5 (Excoffier and Lischer, 2010) including number of haplotypes (N H ), haplotype diversity (h), nucleotide diversity (π), and number of polymorphic sites (N P ).…”

Fitness-related traits are maximized in recently introduced, slow-growing populations of a global invasive clam

“…The invasive lineage (Form A/R) considered in our study includes both diploid and triploid populations, with triploidy being predominant (further details in Pigneur et al, 2014 and references therein; Etoundi et al, 2019). As polyploidy can buffer deleterious mutations and can lead to hybrid vigor (heterosis) with increased fitness (e.g.…”

Identification of the Invasive Form of Corbicula Clams in Ireland

“…The combined methodology of mitochondrial COI sequencing, microsatellite genotyping and morphological analysis has the potential to pick apart the exact identification of genetically complex species groups for which traditional ecological methods may have overlooked complex relationships such as in Corbicula [27] with its highly invasive clonal A/R form. The ability to discriminate between discreet introductions to a geographic area, and secondary spread is an invaluable tool in prioritising AIS biosecurity resources [45] and can inform horizon scanning [46].…”

“…Within invasive populations of Corbicula, further genetic and morphometric complexities can arise from these cryptic hybridizations between sympatric, distinct androgenetic lineages (reviewed in [27]. Indeed, when androgenetic reproduction occurs between two different lineages, the offspring are associated with the nuclear genome and thus, the morphology of the paternal lineage combined to the mitochondrial genome of a distinct maternal lineage, as mitochondria are maternally inherited.…”

“…The high level of phenotypic plasticity present within the invasive forms of Corbicula [22] and the novel reproductive strategies leading to possible cytonuclear mismatches and cryptic hybrids [23] mean any one method on its own from morphology, mitochondrial and microsatellites is likely to provide an incorrect identification of the invasive from tested. The cross-lineage genetic mixing and recent spread of androgenetic Corbicula lineages [27] and the presence of mismatches between mitochondrial and nuclear markers [11,23,28] further demonstrates the need for a multimethod approach.…”