COS 174-3 - CANCELLED - Combining a novel reference genome and population genomic data to describe variable genetic structure in Catostomus fish species

Background/Question/Methods

Species are cohesive evolutionary lineages, yet also consist of independently evolving populations. This tension between common identity of a species and independence of populations has long been a major focus of empirical evolutionary studies and of population genetic theory, and is also pertinent to conservation of threatened taxa in spatially structured populations. In this study, we assessed evolutionary cohesion within each of six geographically overlapping Catostomus fish species in rivers in the US mountain west, and compared the spatial distribution of intraspecific genetic variation across species. For this study, we constructed a new reference genome for flannelmouth sucker (C. latipinnis). We generated genotyping by sequencing data for approximately 1500 individual fish from >30 locations, including 6 different species, as well as low coverage whole genome data for 20 individuals. We then used analyses of common and rare genetic variants (SNPs) to quantify genetic differentiation and genetic diversity across populations throughout the Upper Colorado River basin and adjacent basins.

Results/Conclusions

Common genetic variants showed similarly low overall genomic differentiation within the Upper Colorado River basin for all species, although spatial organization of genetic differentiation varied across species. Higher overall within-species genetic differentiation was identified in species with geographic ranges that span multiple major river basins. For species sampled in both native and introduced ranges, introduced populations had slightly lower per-population genetic diversity, but had higher intra-basin genetic variation. We also used rare genetic variants to examine fine-scale, recent connectivity between river basins. Our results indicated different rates of rare allele sharing across populations, and therefore suggested different dispersal rates and population connectivity, for the two threatened native species (C. latipinnis and C. discobolus, flannelmouth and bluehead suckers). The complementary approaches used with our dataset allowed us to describe different scales of population genetic structure, corresponding to different timescales of genetic differentiation and encompassing both recent and more evolutionarily distant intraspecific genetic differentiation. These results can potentially contribute to ongoing conservation efforts to preserve native Catostomus sucker diversity in the face of threats from introduced species and ecological disturbances.