Using species-diagnostic SNPs to detail the distribution and dynamics of hybridized black bass populations in southern Africa

Abstract

The widespread introduction of Largemouth Bass (Micropterus salmoides) and Florida Bass (M. floridanus) to establish sport fisheries represents a significant conservation concern given their role as apex predators and their ability to alter community diversity and species abundance. In regions like southern Africa, which has both high levels of aquatic endemism and imperilment, limiting the spread of invasive predators is a primary goal of current alien species legislation. Here, we applied two panels of species-diagnostic SNPs for a total of 60 markers to map the distribution of Largemouth Bass, Florida Bass, and their hybrids in 13 southern African water bodies. Using Bayesian clustering algorithms we documented the introgression of Florida Bass alleles across a broad geographic range, from the Cape Floristic region of South Africa to Mozambique. Several populations previously considered pure Largemouth Bass based on mitochondrial DNA sequences were found to consist exclusively of hybrids. Samples collected from Lake Chicamba, which was initially established with pure Largemouth Bass, are now almost exclusively comprised of Florida Bass alleles (89.3 % Florida Bass). The estimated hybrid class of sampled fish (e.g., F1 hybrid, pure Largemouth Bass, pure Florida Bass) showed that with few exceptions, populations were dominated by a single hybrid class. The present work provides enhanced resolution of the distribution and dynamics of Florida Bass, Largemouth Bass, and their hybrids in southern Africa.