Rhyacotriton variegatus

The genus Rhyacotriton previously contained a single species R. olympicus. Based on genetic differentiation, Good and Wake (1992) split olympicus into 4 species.: R. olympicus, R. variegatus, R. kezeri, and R. cascadae. Highton (2000) interpreted their data as showing that R. cascadae likely encompasses two species.

Good and Wake (1992) removed Rhyacotriton from the family Dicamptodontidae and established it as the sole member of the family Rhyacotritonidae.

This species has a small range in western Oregon and northern California. It still occurs throughout its historical range and is common in places, but logging and associated sedimentation and increased water temperatures have led to some localized extirpations and reductions in abundance. Threats from logging are likely decreasing, but the species faces new threats from climate change and marijuana cultivation. Furthermore, it has narrow habitat requirements and with low reproductive rates and dispersal abilities it is slow to colonize new areas. Information on population size and trends is limited.

The southern torrent salamander occurs from southern Mendocino County, California, USA, near Port Arena, through the Coast Ranges to the Little Nestucca River and the Grande Ronde Valley in Polk, Tillamook, and Yamhill counties, Oregon, where the range abuts that of R. kezeri (Emel et al. 2019, Halstead et al. 2020, iNaturalist 2022, ORBIC 2022). It also occurs along the West Slope of the Cascades as far north as the Middle Fork of the Willamette River east of Eugene (Wagner 2001, ORBIC 2022). It is known from Mendocino, Siskiyou, Humboldt and Del Norte Counties in California, and Benton, Coos, Curry, Douglas, Josephine, Lane, Lincoln, Polk, Tillamook, and Yamhill Counties in Oregon. It is patchily distributed in headwaters and low order tributaries (Welsh and Lind 1996).

The species was present at 80.3% of randomly selected headwater streams in one study in coastal northern California (Diller and Wallace 1996). Although Oregon does not currently track element occurrences for this species, there are over 200 known observation records in the state that would distill to approximately 80 element occurrences. Approximately 25% of these observations are post-2000 (ORBIC 2022).

The southern torrent salamander is extremely sensitive to temperature increases and increased siltation that can be caused by timber harvest, road construction and maintenance (Welsh and Oliver 1998, Ashton et al. 2006, Bury 2008, Welsh and Hodgson 2008, Bury 2015, Welsh et al. 2019). Timber harvest is associated with increased sedimentation, habitat fragmentation, and water temperature, and leads to reduced relative abundance of this species (Ashton et al. 2006, Bury 2008, Emel et al. 2019, Welsh et al. 2019). Clear cutting can lead to water temperatures that are above the lethal limits for this species (Bury 2008). Forest fertilizers can be lethal to this species (Marco et al. 2001). Roads, including those associated with timber harvest, increase siltation and present an impassable barrier, limiting dispersal, fragmenting populations and increasing genetic isolation (Wagner 2001, Emel et al. 2019). They can also negatively impact the species by increasing sedimentation. However, the species can persist in some areas after timber harvest, and management for the Northern Spotted Owl (Strix occidentalis caurina) and Marbled Murrelet (Brachyramphus marmoratus) likely benefits this species (Diller and Wallace 1996, USFWS 2000).

Because of limited dispersal abilities and long generation times, populations are vulnerable to fragmentation and genetic isolation; roads and non-forest habitat are impassable (Diller and Wallace 1996, Emel et al. 2019). Drought, flow modification, and water diversion associated with climate change or marijuana cultivation can render sites unsuitable (Bauer et al. 2015, Bury 2015). Water diversion for marijuana cultivation reduces habitat, alters headwater stream flow, and exacerbates effects of climate change (Bauer et al. 2015). Increased temperatures associated with climate change are likely to result in a decrease in the amount of suitable habitat and a reduced range for this species (Bury 2015).