Integrating molecular and archival approaches to uncover native diversity in cutthroat trout

Authors: Jessica L. Metcalf, Sierra Love Stowell, Chris M. Kennedy, Kevin B. Rogers, Andrew P. Martin

Year: 2012 (xliv)

Abstract

Effective conservation efforts require knowledge of species’ historical diversity and distribution. For some species, many populations were extirpated or individuals moved beyond their native range before native diversity and distribution were documented, resulting in a lack of accurate information for establishing conservation goals. Moreover, traditional taxonomic assessments often failed to accurately capture phylogenetic diversity. We illustrate a general approach for estimating regional native diversity and distribution for cutthroat trout, Oncorhynchus clarkii, in the Southern Rocky Mountains. We assembled a large archive of historical records documenting human-mediated change in the distribution of cutthroat trout. We combined these stocking data with phylogenetic analysis of both 19th-century samples collected prior to trout stocking activities and contemporary DNA samples. Our study uncovered six divergent lineages of cutthroat trout in the Southern Rocky Mountains, two of which are extinct. A third lineage, previously declared extinct, was discovered surviving in a single stream outside of its native range. Comparison of the historical and modern distributions with stocking records revealed that the current distribution of trout largely reflects intensive stocking early in the late 19th and early 20th century from two phylogenetically and geographically distinct sources. Our documentation of recent extinctions, undescribed lineages, errors in taxonomy and dramatic range changes induced by human movement of fish underscores the importance of the historical record when developing and implementing conservation plans for threatened and endangered species.