Conservation Genomics of Spikedace (Meda fulgida)

Authors: Alex Cameron, Megan Osborne, Thomas Turner

Year: 2022

Abstract

Spikedace (Meda fulgida) is a small-bodied minnow endemic to the Gila River Basin (Arizona and New Mexico). Spikedace experienced geographic range contraction and declines in abundance in response to alterations of river flow and habitat, and coincident introduction of non-native species. To evaluate levels of genetic diversity, effective population size (Ne), and population structure we performed RAD-sequencing on 196 individuals from remaining wild populations and introduced populations. Genomic data consisted of 11,074 biallelic SNPs distributed across 25 chromosomes. Distinct lineages of Spikedace are present in Aravaipa Creek and the Upper Gila River. Aravaipa Creek retains the most genomic variation, suggesting long-term demographic stability compared with other wild populations. We found little evidence for natural selection contributing to the observed population structure. We recovered large effective population size estimates (Ne > 500) for wild populations in each lineage of Spikedace. However, there was considerable variability in Ne estimates among introduced populations, where two populations had low effective sizes (Ne ≤ 100), but a third exhibited Ne > 500. Overall, these data highlight how demographic stochasticity contributes to genetic population structure among desert fishes.