Impacts of habitat loss on genetic diversity of ETHEOSTOMA LEMNISCATUM, the Tuxedo Darter

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Austin Peay State University
Habitat loss and alteration is often detrimental to the genetic diversity of species within the impacted area, especially those species considered imperiled due to other factors, such as a naturally small native range. For imperiled fish species in the southeastern United States, damming of rivers is a leading form of habitat alteration that poses a major conservation issue for many riverine adapted species. Dams homogenize habitat and alter natural riverine flow regimes. The Tuxedo Darter, ETHEOSTOMA LEMNISCATUM, is a federally endangered fish species that inhabits the mainstem of the Big South Fork Cumberland River in Kentucky and Tennessee. The species is considered a habitat-specialist, adapted to survive and reproduce in shallow pools with clean, cobble substrate. It is threatened by damming of the Cumberland River to create Lake Cumberland, which during summer pool, inundates the lower 8 rkm of the species’ range. To determine the impact of inundation on E. LEMNISCATUM, we compared occurrence, abundance, and genetic diversity metrics estimated from pre- (2015) and post-inundation (2019/2020; four years after inundation) samples from eleven sites spanning the species’ range. We expected to see a reduction in occurrence, abundance and genetic diversity and increased inbreeding as a response to inundation. Declines in occurrence and abundance were detected within the impacted reach. Standard and temporal comparisons of genetic diversity metrics stemming from our genotypic data from 20 microsatellite loci for the 92 individuals collected in 2019 and 2020 and data from the 107 individuals collected in 2015 (provided by Washburn et al. 2020) revealed low genetic diversity for the species. No significant changes in genetic diversity between years was detected. However, in addition to observations of local extirpation and declines in abundance in the impacted reach, early warning signs of genetic diversity degradation, such as lowered allelic richness and an increase in the proportion of private alleles, were also observed in the impacted reach. These early warning signs indicate a likelihood of impacts to genetic diversity in future generations. Our results warrant further monitoring of the species to determine any time delayed responses to inundation that were not detected in this study.
Darters (Fishes) -- Effect of habitat modification on, Cumberland River, Big South Fork (Tenn. and Ky.)