Genetic analysis and uncertain taxonomic status of threatened Foskett Spring speckled dace

Abstract

Foskett Spring is a small isolated desert spring in the Warner Basin of Oregon containing an undescribed subspecies of speckled dace protected under the US Endangered Species Act. Uncertainty regarding the taxonomic status of Foskett dace has raised questions about their evolutionary relationship to other more abundant populations in the Warner Basin. To address these questions, we sequenced 1,982 base pairs (bp) of the ND2 and cyt-b genes of mitochondrial DNA (mtDNA) for 85 fish from Foskett Spring, the surrounding Warner Basin, and the adjacent Goose Lake Basin. We observed 58 unique mtDNA haplotypes defined by 96 bp substitutions in both genes. MtDNA sequences were highly divergent and reciprocally monophyletic between dace from the Warner and Goose Lake Basins, with sequence divergences (5 and 3% at ND2 and cyt-b, respectively) in the range usually observed between fish species. In contrast, mean sequence divergence between Foskett dace and other Warner Basin populations was less than 1%, with no evidence of reciprocal monophyly among mtDNA lineages. These results indicate that Foskett dace and other populations in the Warner Basin are approximately equally diverged from one another evolutionarily, suggesting similar times of divergence since the late Pleistocene. We believe further studies are needed to determine if rapid evolution of novel traits have occurred in dace inhabiting the unique ecological setting of Foskett Spring during the past 10,000 years.

Population Structure in the Roundtail Chub (Gila robusta Complex) of the Gila River Basin as Determined by Microsatellites: Evolutionary and Conservation Implications

“…In their study of mtDNA variation in Richardsonius , Houston et al [ 56 ] found most variation distributed among, but not within, major regions, indicating high levels of gene exchange within but not among regions. This contrasts with studies of other minnows (e.g., Rhinichthys osculus –[ 57 , 58 ] and Lepidomeda –[ 59 ]), where there was considerable divergence among localities within drainages as well as among drainages. Johnson [ 60 ] also identified considerable divergence within and among drainage groups in the cyprinid Gila atraria but also noted additional divergence associated with evolved life history differences within this species.…”

Going, going, gone? Loss of genetic diversity in two critically endangered Australian freshwater fishes, Scaturiginichthys vermeilipinnis and Chlamydogobius squamigenus, from Great Artesian Basin springs at Edgbaston, Queensland, Australia

“…These levels of genetic diversity may not be unusual in spring biota, as they exist in very isolated and small habitat patches and undergo strong selection pressure to adapt to local conditions. Further examples include a study of speckled dace from Foskett Springs, USA that also detected three cytb haplotypes (Arden et al , ), and haplotype diversity per spring group was also found to be relatively low in the Trochidrobia spring snails (Murphy et al , ), and the Bitter Lake National Wildlife Refuge endemic spring snails (Morningstar et al , ). Even though low levels of cytb diversity may be the natural evolutionary state for spring biota, further population genetic monitoring of Edgbaston goby is advised as recent surveys have suggested it is also in decline across the spring system (Kerezsy, ).…”

Population genomic analysis of the Speckled Dace species complex identifies three distinct lineages in California

“…More narrowly, Ardren et al (2010) applied mtDNA analysis to dace from throughout the Warner Basin and concluded that the lineages could collectively qualify as a species. Hoekzema and Sidlauskas (2014) also examined SDC fish from the Warner Basin along with dace from five other isolated Great Basin populations in Oregon.…”