Multiscale Genetic Structure of Yellowstone Cutthroat Trout in the Upper Snake River Basin

Abstract

Abstract.-Populations of Yellowstone cutthroat trout Oncorhynchus clarkii bouvierii have declined throughout their native range as a result of habitat fragmentation, overharvest, and introductions of nonnative trout that have hybridized with or displaced native populations. The degree to which these factors have impacted the current genetic population structure of Yellowstone cutthroat trout populations is of primary interest for their conservation. In this study, we examined the genetic diversity and genetic population structure of Yellowstone cutthroat trout in Idaho and Nevada with data from six polymorphic microsatellite loci. A total of 1,392 samples were analyzed from 45 sample locations throughout 11 major river drainages. We found that levels of genetic diversity and genetic differentiation varied extensively. The Salt River drainage, which is representative of the least impacted migration corridors in Idaho, had the highest levels of genetic diversity and low levels of genetic differentiation. High levels of genetic differentiation were observed at similar or smaller geographic scales in the Portneuf River, Raft River, and Teton River drainages, which are more altered by anthropogenic disturbances. Results suggested that Yellowstone cutthroat trout are naturally structured at the major river drainage level but that habitat fragmentation has altered this structuring. Connectivity should be restored via habitat restoration whenever possible to minimize losses in genetic diversity and to preserve historical processes of gene flow, life history variation, and metapopulation dynamics. However, alternative strategies for management and conservation should also be considered in areas where there is a strong likelihood of nonnative invasions or extensive habitat fragmentation that cannot be easily ameliorated.

Biology, Status, and Management of the Yellowstone Cutthroat Trout

“…Wofford et al (2005) reported that gene diversity and allelic richness of coastal cutthroat trout in a 2,200-ha watershed were lowest in small tributaries where immigration had been blocked by culverts. Similarly, genetic diversity and genetic population structure of Yellowstone cutthroat trout from 45 sites in streams of Idaho and Nevada appeared to be naturally structured at the major river drainage scale, but structure was altered by habitat fragmentation (Cegelski et al 2006). Furthermore, fragmentation can destroy critical dispersal pathways among populations, preventing repopulation after local extirpation (Guy et al 2008).…”

“…For example, the system with the least-altered migration corridors (among the 11 major river drainages in the study) exhibited the highest levels of genetic diversity and low levels of genetic differentiation. High levels of genetic differentiation were observed at similar or smaller geographic scales in stream networks that were more altered by anthropogenic activities (Cegelski et al 2006).…”

Comparative biogeography reveals differences in population genetic structure of five species of stream fishes

“…In contrast, intrinsic factors such as life‐history characteristics, demographic history, and response to habitat attributes are not expected to be reflected in all the species in a given area (Neville, Dunham & Peacock, ; Dionne et al ., ; Haponski et al ., ). Anthropogenic factors can both partition genetic variation through the construction of barriers to migration (Reid et al ., ; Beneteau, Mandrak & Heath, ) and eliminate population structure through human‐mediated dispersal (van Houdt et al ., ; Cegelski et al ., ; Clemento et al ., ). The interaction of these factors can make it difficult to interpret biogeographical patterns of a region.…”

Genetic population structure and evidence of genetic homogeneity in populations of the Argentinian silverside Odontesthes bonariensis (Teleostei: Atherinopsidae) inhabiting central and northwestern Argentina

“…suggested that this intervention may alter the genetic signals of species by increasing or decreasing population connectivity. For example, perturbations in __________________ Corresponding editor: Marcelo Vianna the landscape, such as dams, may limit species migration (Reid et al, 2008;Beneteau et al, 2009), while assisted dispersion due to intentional or accidental introductions may increase connectivity artificially in freshwater systems (Cegelski et al, 2006;Husemann et al, 2012;Crook et al, 2015). These changes alter the natural dispersion of the species and natural population structure (Walter et al, 2009;Husemann et al, 2012).…”