Lack of gene flow: Narrow and dispersed differentiation islands in a triplet of Leptidea butterfly species. Issue 16 (8th August 2019)

• Record Type: Journal Article
• Authors: Talla, Venkat; Johansson, Anna; Dincă, Vlad; Vila, Roger; Friberg, Magne; Wiklund, Christer; Backström, Niclas
• Is Part Of: Molecular ecology. Volume 28:Issue 16(2019)
• Page Start: 3756
• Page End: 3770
• Publication Date: 2019-08-08
• Subjects: cryptic species -- genome scan -- Lepidoptera -- Leptidea -- speciation -- wood white butterflies; Molecular ecology -- Periodicals; Molecular population biology -- Periodicals; 576
• DOI: 10.1111/mec.15188
• Languages: English
• ISSNs: 0962-1083

Abstract

Abstract: Genome scans in recently separated species can inform on molecular mechanisms and evolutionary processes driving divergence. Large‐scale polymorphism data from multiple species pairs are also key to investigate the repeatability of divergence—whether radiations tend to show parallel responses to similar selection pressures and/or underlying molecular forces. Here, we used whole‐genome resequencing data from six wood white ( Leptidea sp.) butterfly populations, representing three closely related species with karyomorph variation, to infer the species' demographic history and characterize patterns of genomic diversity and differentiation. The analyses supported previously established species relationships, and there was no evidence for postdivergence gene flow. We identified significant intraspecific genetic structure, in particular between karyomorph extremes in the wood white ( L. sinapis )—a species with a remarkable chromosome number cline across the distribution range. The genomic landscapes of differentiation were erratic, and outlier regions were narrow and dispersed. Highly differentiated ( F ST ) regions generally had low genetic diversity ( θπ ), but increased absolute divergence ( DXY ) and excess of rare frequency variants (low Tajima's D ). A minority of differentiation peaks were shared across species and population comparisons. However, highly differentiated regions contained genes with overrepresented functions related to metabolism, response to stimulus and cellular processes, indicating recurrent directional selection on a specific set of traits in all comparisons. In contrast to the majority of genome scans in recently diverged lineages, our data suggest that divergence landscapes in Leptidea have been shaped by directional selection and genetic drift rather than stable recombination landscapes and/or introgression.