Exploring the phylogeography of a hexaploid freshwater fish by RAD sequencing

The KwaZulu-Natal yellowfish (Labeobarbus natalensis) is an abundant cyprinid, endemic to KwaZulu-Natal Province, South Africa. In this study we developed a Single Nucleotide Polymorphism (SNP) dataset from double-digest Restriction-site Associated DNA (ddRAD) sequencing of samples across the distribution. We addressed several hidden challenges, primarily focussing on proper filtering of RAD data and selecting optimal parameters for data processing in polyploid lineages. We used the resulting high-quality SNP dataset to investigate the population genetic structure of L. natalensis. A small number of mitochondrial markers present in these data had disproportionate influence on the recovered genetic structure. The presence of singleton SNPs also confounded genetic structure. We found a well-supported division into northern and southern lineages, with further subdivision into five populations, one of which reflects north-south admixture. Approximate Bayesian Computation scenario testing su...