Whole-genome re-sequencing data to infer historical demography and speciation processes in land snails: the study of twoCandidulasister species

Abstract

Despite the global biodiversity of terrestrial gastropods and their ecological and economic importance, the genomic basis of ecological adaptation and speciation in land snail taxa is still largely unknown. Here, we combined whole-genome re-sequencing with population genomics to evaluate the historical demography and the speciation process of two closely related species of land snails from western Europe, Candidula unifasciata and C. rugosiuscula . Historical demographic analysis indicated fluctuations in the size of ancestral populations, probably driven by Pleistocene climatic fluctuations. Although the current population distributions of both species do not overlap, our approximate Bayesian computation model selection approach on several speciation scenarios suggested that gene flow has occurred throughout the divergence process until recently. Positively selected genes diverging early in the process were associated with intragenomic and cyto-nuclear incompatibilities, respectively, potentially fostering reproductive isolation as well as ecological divergence. Our results suggested that the speciation between species entails complex processes involving both gene flow and ecological speciation, and that further research based on whole-genome data can provide valuable understanding on species divergence. This article is part of the Theo Murphy meeting issue ‘Molluscan genomics: broad insights and future directions for a neglected phylum’.

Whole‐genome analysis of multiple wood ant population pairs supports similar speciation histories, but different degrees of gene flow, across their European ranges

“…In such cases, reconstructing the divergence history between the two species would depend on the geographic location of the set of populations sampled, because populations also evolve in space (see Bradburd & Ralph, 2019 for a recent review on spatial population genetics). While some studies have previously reconstructed the speciation history between several species using multiple population pairs (e.g., Chueca et al, 2021;Filatov et al, 2016;Garcia-Erill et al, 2021;Ito et al, 2020;Pabijan et al, 2017;Rougemont & Bernatchez, 2018;Stankowski et al, 2020;Zieliński et al, 2016), to our knowledge variation inferred between the multiple comparisons has not been reported. In this study, we investigate how the divergence history between two species may vary depending on the geographic location of the pair of heterospecific populations considered, using mound-building red wood ants.…”

De novogenome assembly of the land snailCandidula unifasciata(Mollusca: Gastropoda)

“…Although, there are many taxonomical, phylogeographical, and evolutionary studies concerning Geomitridae species ( Pfenninger and Magnin 2001 ; Sauer and Hausdorf 2010 ; Brozzo et al 2020 ), the lack of reference genomes makes it difficult to investigate deeper biological and evolutionary questions about geomitrids and other land snails species. Here, we present the annotated draft genome of C. unifasciata that will be a valuable resource for future genomic research of this important taxonomic group ( Chueca et al 2021 ).…”

Pearls of wisdom—a Theo Murphy issue on molluscan genomics

“…Genome resequencing is now routine in other taxa, but large genome size and lack of reference assemblies have limited the ability to apply resequencing to molluscs. The study by Chueca et al [14] is thus an illustration of what will soon be commonplace: the wider application of resequencing methods in molluscs. Indeed, we anticipate the execution of studies that are as ambitious as those that have used Littorina as a model to understand speciation over many years [15], but requiring considerably less resources.…”