Phenotypic differences between historic and refuge populations of Pahrump Poolfish.

Authors: Shawn C.* Goodchild, Craig A. Stockwell

Year: 2015 (xlvii)

Abstract

The establishment of refuge populations as a hedge against extinction has been a common management technique for desert fishes. Such managed relocation has been debated for narrowly endemic aquatic species, and unintended rapid phenotypic divergence of the translocated population has been demonstrated in ex situ populations. Such divergence begs the question of whether these populations are suitable as potential source stock for reintroduction to the original habitat. One species that has undergone a complex history of translocations is the Pahrump Poolfish (Empetrichthys latos latos). Dr. James Deacon, along with a coalition of State, Federal, and other entities, removed Poolfish from Manse Spring prior to its desiccation, effectively saving the genus Empetrichthys from extinction. From its initial holding at the University of Nevada, Las Vegas, several refuges have been established in drastically different habitats. We investigated size and life history characteristics of two of the populations, the high latitude and elevation Shoshone Stock Pond and the low latitude and elevation Lake Harriet, to determine potential differences. We then compared these results with reported characteristics from the historic Manse Spring population. There were substantial differences among the three sites in life history, as well as in size and phenology. This phenotypic divergence has occurred within several decades and may reflect relict, plastic or evolutionary responses to environmental factors such as temperature and/or fish density. As such, more attention is needed to assess if phenotypic divergence of refuge populations may result in a phenotypic mismatch to prospective additional refuge habitats and/or reintroduction to their native habitat. Alternatively, these refuges could function as a novel ecosystem, and may be beneficial to provide resilient stock in light of large-scale habitat change, such as predicted from climate change or utilization in different refuge environments.