The conservation genetics of Ash Meadows pupfish populations. I. The Warm Springs pupfish Cyprinodon nevadensis pectoralis

The Warm Springs pupfish (Cyprinodon nevadensis pectoralis) inhabits several low flow (<0.15 cfs) springs in an otherwise dry Mojave Desert landscape. Increasing demands on groundwater coupled with predictions of decreased precipitation from global warming make this species a sentinel for biodiversity dependent on springs. Here we examine mitochondrial DNA haplotypes and nuclear microsatellite genotypes for individuals sampled in 1998 and 2007 as a means of inferring the historical demography of the subspecies. Estimates of genetic effective population size from comparison of allele frequencies over time underscores that all spring populations support small populations, typically <100 individuals. Such small population sizes suggest spring populations may have heightened probabilities of extirpation. Despite small population sizes, all springs harbor relatively high levels of genetic variation for both nuclear and mitochondrial DNA. Unexpectedly high levels of variation may be explained by recent declines in population size coupled with rare episodes of gene flow between springs suspected of occurring during flooding events. The inferences gained from the genetic data provide the basis for evaluating current and future restoration plans. The genetic data suggest there is a need to balance the predicted positive effects of restoring hydrological connectivity with the potential negative impacts of providing avenues for the spread of exotic species detrimental to pupfish populations.