COS 128-2 - Exploring the Ecological and Evolutionary Impacts of Sustained Invasive Species Suppression

Abstract: Although rapid evolution following heavy harvest has been shown to occur in experimental settings, evidence from nature is less straightforward. Here, we explore the ecological and evolutionary mechanisms through which smallmouth bass (Micropterus dolomieu) populations have persisted in two Adirondack lakes despite extensive removal efforts conducted biannually for the last two decades. Previous work in the system showed that ecological overcompensation was possible due to high young-of-year survival of nest-guarding smallmouth, as well as reduced cannibalism when large individuals were fished out. Here we analyze demographic and life history outcomes of this invader suppression effort and use low-coverage whole-genome sequencing to search for signatures of density-dependent or harvest-induced selection. While there are strong ecological effects of the removal, such as reduced age-at-maturity, altered nest success, and increased somatic growth rates, it remains unclear whether rapid evolutionary changes have facilitated smallmouth persistence. After assembling the first reference genome for the species, our genomic data indicate high levels of genetic drift, consistent with a population maintained by a small number of successful spawners. Furthermore, we also identified regions of elevated allele frequency change and reduced Tajima’s D on several chromosomes, potentially driven by selection. Taken together, our findings indicate that rapid trait shifts have facilitated the persistence of this invasive predator despite sustained removal efforts.