Islands in the desert: assessing fine scale population genomic variation of a group of imperiled desert fishes

The genus Crenichthys (Teleostei: Goodeidae) is an imperiled group of desert spring specialist fishes currently containing two species and five subspecies, found within only a few of the relictual springs distributed throughout the Great Basin of North America. Threatened by multiple forms of human disturbance, including habitat destruction, invasive species, and pollution, the need to better understand their population structure is immediate. This is further emphasized by previous research that demonstrated that the current taxonomy of Crenichthys needs re-evaluation and that genetic substructure may be present. The genus also represents a perfect opportunity to better understand desert spring habitats. These unique ecosystems often contain a suite of endemics, trapped within individual isolated springs distributed throughout a desert. The assumption is often that each spring will contain genetically distinct populations, however, this is not always true. We used single nucleotide polymorphisms (SNPs) to describe the genetic diversity and structure among populations of the genus Crenichthys with the intent to better understand the patterns of diversity within desert endemic fishes. Our results corroborated previous research suggesting genetic divergence between two groups within both C. baileyi and C. nevadae . It further demonstrated that many of the populations are genetically similar, likely due to a combination of short divergence time and possible past admixture.