The endangered White Sands pupfish (Cyprinodon tularosa) genome reveals low diversity and heterogenous patterns of differentiation

The White Sands pupfish (Cyprinodon tularosa), endemic to New Mexico in Southwestern North America, is of conservation concern due in part to invasive species, chemical pollution, and groundwater withdrawal. Herein, we developed a draft reference genome and use it to provide biological insights into the evolution and conservation of C. tularosa. We used our assembly to localize microsatellite markers previously used to demarcate evolutionary significant units (ESU), quantified genomic divergence and transposable element profiles between species, and compared C. tularosa genomic diversity related species. Our de novo assembly of PacBio Sequel II error-corrected reads resulted in a 1.08 Gb draft genome with a contig N50 of 1.4 Mb and 25,260 annotated protein coding genes, including 95% of the expected Actinopterygii conserved complete single-copy orthologues. Many of the C. tularosa microsatellite markers used for conservation assessments fell within, or near, genes and exhibited a pattern of increased heterozygosity near genic areas compared to those in intergenic regions. Nuclear alignments between these two species revealed 193 genes contained in rapidly diverging tracts; transposable element profiles were largely concordant and suggest a shared, rapid expansion of LINE and Gypsy elements. Genome-wide heterozygosity was markedly lower in C. tularosa compared to estimates from other related species, probably because of smaller long-term effective population sizes constrained by their isolated and limited habitat. Overall, these inferences provide new insights into C. tularosa that should help inform future management efforts.

Automated summary

Researchers developed a draft reference genome of the White Sands pupfish to study its evolution and conservation. They compared genomic divergence and transposable element profiles between species, finding lower genome-wide heterozygosity in the White Sands pupfish compared to other related species, possibly due to its isolation and limited habitat.