Population structure and genetic management of Rio Grande cutthroat trout (Oncorhynchus clarkii virginalis)

Abstract

The Rio Grande cutthroat trout, Oncorhynchus clarkii virginalis, has declined precipitously over the past century, and currently exhibits a highly fragmented distribution within the Canadian, Pecos and Rio Grande river systems of the western United States. The relationships between populations in the three river drainages, and between O. c. virginalis and the closely related taxa O. c. pleuriticus and O. c. stomias, are not well understood. In order to guide management decisions for the subspecies, we investigated the distribution of variation at 12 microsatellite loci and two regions of the mitochondrial genome. We observed a high level of genetic differentiation between O. c. virginalis populations occupying different headwater streams (global F st = 0.41). However, we found evidence for previous gene flow within the Rio Grande drainage, indicating that inter-population differentiation may have been exacerbated by the recent effects of population fragmentation. Despite large-scale anthropogenic movement of individuals from the Rio Grande into the Canadian and Pecos, the genetic signature of long-term evolutionary independence between the three drainages has been retained.

Predicting Persistence of Rio Grande Cutthroat Trout Populations in an Uncertain Future

“…Maintaining these peripheral populations is important (Haak and Williams ), not only for the genetic (Pritchard et al. , ) and morphological (Bestgen et al. ) diversity they display but also for the potential ecological diversity that is yet unmeasured (e.g., thermal tolerance).…”

“…Most remaining populations are isolated in high‐elevation headwater streams, resulting in decreased genetic diversity within populations and increased genetic differentiation among them (Pritchard et al. , ). Continued threats to the subspecies have resulted in multiple petitions to list RGCT for protection under the Endangered Species Act, with recent findings focused on the consequences of a warming climate (USFWS , ).…”

Conservation of Native Pacific Trout Diversity in Western North America

“…Advances in molecular genetic techniques and associated analyses over the last several decades have given rise to new hypotheses regarding taxonomic relationships and revealed increased species diversity (Allendorf and Leary 1988;Crespi and Fulton 2004;Crête-Lafrenière et al 2012). However, the taxonomy of Pacific trout in western North American is subject to ongoing debate (Metcalf et al 2007;Pritchard et al 2008;Loxterman and Keeley 2012). For example, recent studies used century-old museum collections to define the native range and diversity of lineages in the southern Rocky Mountains for Greenback, Colorado River, and Yellowfin Cutthroat trouts (Metcalf et al 2012;Bestgen et al 2013), and this information is being used to identify extant native populations and to guide the search for remaining pockets of diversity.…”

Full Issue PDF, Volume 41, Issue 6

“…Advances in molecular genetic techniques and associated analyses over the last several decades have given rise to new hypotheses regarding taxonomic relationships and revealed increased species diversity Crespi and Fulton 2004;Crête-Lafrenière et al 2012). However, the taxonomy of Pacific trout in western North American is subject to ongoing debate (Metcalf et al 2007;Pritchard et al 2008;Loxterman and Keeley 2012). For example, recent studies used century-old museum collections to define the native range and diversity of lineages in the southern Rocky Mountains for Greenback, Colorado River, and Yellowfin Cutthroat trouts (Metcalf et al 2012;Bestgen et al 2013), and this information is being used to identify extant native populations and to guide the search for remaining pockets of diversity.…”