Clones on the run - the genomics of a recently expanded facultative asexual species

Abstract

Why, in facultative asexual species, marginal populations are often richer in clones than are core populations, remains unclear. Cloning freezes genotypes but hampers recombination and local adaptation. During expansion, clones are favoured over non-selfing sexuals by uniparental reproduction. To better understand the dynamics of clones and sexual lineage, we used genome-wide sequencing to analyse a recently expanded seaweed. We found large clones and sexual populations mixed close to range margins. Clones had evolved repeatedly from sexual populations but were unexpectedly low in genetic variation. Modelling suggested clones form from sexual populations after repeated bottlenecks at the expansion front. A clonal wave of depauperate genotypes thereafter spread ahead of the sexual population. As we observed, these early formed clones may survive side-by-side sexual individuals, which suggests they lost their sexual capacity. Our study illustrates how range expansion can result in complex and dynamic patterns of genetic variation in facultative asexual species.TeaserWe use genome data and modelling to find out why large clones are only found at range margins in a recently expanded seaweed

Mixed origin of juvenile Atlantic cod (Gadus morhua) along the Swedish west coast

“…Trimming, filtering, and genotype calling was done following Pereyra et al (2022). Trimmed and quality-filtered sequences were mapped to the cod genome assembly gadMor3.0 (NCBI Bioproject accession no.…”

“…Technical replicates rendered 15 320 SNPs that were used as "true" SNP dataset for recalibration of variants. A total of 55 449 SNPs were called, and a set of 23 364 SNP loci and 235 individuals was obtained after filtering following Pereyra et al (2022). Subsequent removal of loci with a minor allele frequency < 5 % resulted in 9956 SNP loci for downstream analyses.…”