Phylogeography and Spatial Genetic Structure of the Southern Torrent Salamander: Implications for Conservation and Management

Abstract

The Southern torrent salamander (Rhyacotriton variegatus) was recently found not warranted for listing under the US Endangered Species Act due to lack of information regarding population fragmentation and gene flow. Found in small-order streams associated with late-successional coniferous forests of the US Pacific Northwest, threats to their persistence include disturbance related to timber harvest activities. We conducted a study of genetic diversity throughout this species' range to 1) identify major phylogenetic lineages and phylogeographic barriers and 2) elucidate regional patterns of population genetic and spatial phylogeographic structure. Cytochrome b sequence variation was examined for 189 individuals from 72 localities. We identified 3 major lineages corresponding to nonoverlapping geographic regions: a northern California clade, a central Oregon clade, and a northern Oregon clade. The Yaquina River may be a phylogeographic barrier between the northern Oregon and central Oregon clades, whereas the Smith River in northern California appears to correspond to the discontinuity between the central Oregon and northern California clades. Spatial analyses of genetic variation within regions encompassing major clades indicated that the extent of genetic structure is comparable among regions. We discuss our results in the context of conservation efforts for Southern torrent salamanders.

Sources of uncertainty in stream-associated amphibian ecology and responses to forest management in the Pacific Northwest, USA: A review

“…How far can SAA disperse and over what time period? These and other questions are of critical importance, and would complement completed work on genetic structure of SAA populations (Curtis and Taylor, 2004;Miller et al, 2006;Wagner et al, 2006).…”

Range-wide phylogeographic analysis of the spotted frog complex (Rana luteiventris and Rana pretiosa) in northwestern North America

“…The timing of this split appears to be linked to Cascade orogeny (Carstens et al, 2004. Coastal and Cascade species also show north-south breaks that have been attributed to isolation in Pleistocene refugia (Brunsfeld et al, 2001;Steele and Storfer, 2006) and by rivers (Miller et al, 2006b;Monsen and Blouin, 2003). Further to the east, a phylogeographic break has been found between the Great Basin (in southeastern Oregon, southern Idaho, Nevada, and northern Utah) and northern Rockies (to the north of the Great Basin; Swenson and Howard, 2005).…”

Red- and yellow-footed tortoises, Chelonoidis carbonaria and C. denticulata (Reptilia: Testudines: Testudinidae), in South American savannahs and forests: do their phylogeographies reflect distinct habitats?

“…Phylogeographic investigations can provide valuable insights about historical and geographic factors shaping genetic diversification across a species' range and improve our understanding of shifting environments over time (Avise 2000;Haig et al 2004;Miller et al 2006;Ripplinger and Wagner 2004). For Amazonian forest species, genetic evaluations and dating of their divergence have been used for inferring the biogeographic history of the Amazonian rainforest (Moritz et al 2000), while non-forest species have been relatively neglected (Pennington et al 2000(Pennington et al , 2004.…”