Assessing the Range-wide Genetic Diversity of Relict Dace (Relictus solitarius), a Desert Endemic Minnow Influenced by Pluvial Drainage Patterns, Holocene Desiccation, and Anthropogenic Activities

Authors: Derek D. Houston, R. Paul Evans, Dennis K. Shiozawa

Year: 2016 (xlviii)

Abstract

Desert fishes often represent unique evolutionary lineages confined to fragmented habitats. The relict dace (Relictus solitarius) is a desert endemic minnow with a native range that is restricted to isolated spring systems in eastern Nevada. The spring systems in which relict dace now reside are the remnants of pluvial lakes that existed during the Pleistocene Epoch, and are contained within four valleys (Butte, Goshute, Ruby, and Steptoe). Relict dace are the only native fish in the area, but largemouth bass and speckled dace have been introduced to water bodies in Ruby Valley. We used DNA sequence data to evaluate rangewide genetic diversity o f relict dace, and to determine whether introgressive hybridization has occurred in areas where speckled dace have been introduced. Our results show that limited introgressive hybridization has taken place in one population, but other relict dace populations in Ruby Valley remain genetically distinct from speckled dace. Rangewide, relict dace populations exhibit pronounced genetic diversity. Initial diversification coincided with pluvial drainage systems, but isolation of populations occurred as pluvial drainages were disrupted and springs became isolated with the onset of Holocene desiccation. Relict dace populations are all genetically distinct, and meet criteria for consideration as evolutionary significant units. These populations should be managed in a way that maximizes the preservation of species-wide genetic diversity, particularly given the increasing demands and influences of anthropogenic activities on aquatic resources in western North American deserts.