Plethodon stormi

Plethodon stormi has been regarded as a subspecies of P. elongatus by some authors (Stebbins 2003). Recent genetic studies (DeGross 2004, Mahoney 2004) support the view that P. elongatus and P. stormi are distinct species. The two taxa are somewhat similar in morphology, but P. stormi mostly have 17 costal grooves compared to 18 in P. elongatus.

Mead et al. (2005) examined morphological and mtDNA variation in Plethodon populations near the California-Oregon border and concluded that P. stormi and P. elongatus are distinct species and that nearby populations in the vicinity of the Scott River in Siskiyou County, California, represent a distinct species, which was described as Plethodon asupak.

Limited to an area of about 1655 sq km in southern Oregon and northern California; threatened by deforestation, increased frequency and intensity of fire, and climate change.

Restricted to the Siskiyou Mountains in southern Oregon (mostly upper Applegate River drainage, Jospehine and Jackson counties) and northern California (Siskiyou County: near Hutton Guard Station, the Cook and Green Guard Stations, along Joe and Dutch creeks in upper Applegate River drainage and along Seiad and Horse creeks in Klamath River drainage) (California Department of Fish and Game 1990). In Oregon, found at elevations from 490-1,463 m (Leonard et al. 1993).

Surveys conducted by the US Forest Service, US Fish and Wildlife Service, and the California Department of Fish and Wildlife (CDFW) suggest that there are 300 known occurrences. 70 are located in Oregon and 230 in California.

Key Threats: Habitat loss, degradation, and additional fragmentation of discrete populations are all potential threats to this species. Activities that may pose threats are those that disturb the surface microhabitats and/or microclimate conditions. Typically these involve actions that remove canopy and/or disturb the substrate. Removal of canopy over-story may cause desiccation of the rocky substrates and loss of the moss ground cover, a microhabitat feature of P. stormi sites (Olson 2007). Such removal has the potential to occur from timber harvest operations. Fire, fire suppression activities, construction of roads, disease, and climate change are also key threats to P. stormi.

Timber Harvest
Since timber harvesting disturbs more ground than any other land use in the known range of P. stormi, it is perceived to be the primary threat to P. stormi (Nussbaum 1974; California Department of Fish and Game 1987, Blaustein et al. 1994; Bury and Pearl 1999; USDA, USDI Species Review Panel 2001; Greenwald 2004). Timber operations may impact P. stormi directly when P. stormi are on the surface and active during the spring and fall by killing animals during operations or indirectly by reducing habitat suitability and connectivity. Heavy equipment operations can directly disturb talus substrates reducing habitat suitability.

Harvesting removes tree and shrub canopy, which modifies the microhabitat at and potentially below the ground surface (Chen et al. 1999). Approximately 24% (10% private and 14% Federal matrix) of the lands within the currently documented range could be modified by timber harvesting. The majority of the land within the species range is projected to have limited timber harvest under current Klamath National Forest management plans. Analysis of disturbance over the range of P. stormi in California shows that at least 37% of the landscape has been disturbed by fire or timber harvesting; however, they continue to be found in these areas and are reproducing (CDFW 2003).

Fire
Most prehistoric fires were probably low intensity, frequent, and occurred when the animals were not active near the surface, with little consequence for P. stormi. Recent fire suppression has made the landscape more prone to high intensity, stand-replacing fire events that could impact the species (USDA Forest Service 1994b; Taylor and Skinner 1998). Another potential threat to the species is prescribed fire when conducted during the times of the year when they may be active and near the surface.

USFS forest inventory data for the Klamath National Forest (USDA Forest Service 1994b) suggest a historical average high intensity, stand-replacing fire frequency of 110 to 180 years in all forest types. Wildfires occur more frequently during warm dry conditions when P. stormi are unlikely to be at the surface, and so direct mortality is not likely. The loss of tree canopy and organic debris on the soil surface by burning may modify the talus microclimate and interrupt the supply of organic material serving as an energy source for prey organisms. Several decades of fire suppression have likely augmented fuel loading that increase the intensity of fire when it occurs. In this landscape where high intensity stand-replacing fires occurred on a frequency of 110 to 180 years, P. stormi have successfully inhabited the area for a very long time, conservatively three to four million years. No data is available documenting exactly how long P. stormi have occupied any specific location within their range.

Roads
Available information suggests that P. stormi are found in areas with various levels of disturbance. P. stormi are known to occur within disturbed sites, such as rock quarries, log landings, and road and skid road cutbanks and fill-slopes. Due to ease of capture, many animals have been collected from talus banks of road cuts. P. stormi may colonize road cuts soon after road construction, moving in from talus above and below the road. P. stormi move into the road cut only during the wet season or, more likely, were already on site (Nussbaum 1974). Road construction is a likely cause that “take” (Fish & G. Code, § 86) may occur. Emergency operations conducting fire suppression activities may require road construction in areas that may contain suitable P. stormi habitat.

Disease
Chytridiomycosis is a potentially fatal epidermal infection caused by a chytrid fungus, Batrachochytrium dendrobatidis (Bd), which has been found to affect several amphibian populations worldwide. In the United States massive amphibian deaths have been recorded in Arizona, California, and Colorado (Daszak et al. 1999). Although the disease has been responsible for mass mortality, population declines, and species extinction not all infected populations and species are negatively affected (Weldon 2002; Mazzoni et al. 2003) and light infections have also been found on amphibians in the wild which show no clinical signs of the infection (Retallick et al. 2004).

Bd is a member of the phylum Chytridiomycota. Some chytrids are found in water and soil, and contribute significantly to the initial degradation of organic matter such as chitin and keratin while other are parasites of algae, plants, nematodes or insects (Barr 1990). Chytrid fungus infection was reported on a wild-caught, strictly terrestrial salamander. A single adult, gravid female, Jemez Mountains salamander (Plethodon neomexicanus), a species endemic to the Jemez Mountains in New Mexico, was collected in a meadow containing a few aspen trees (Populus tremuloides) (Cummer et al. 2005). Infected tiger salamanders (Ambystoma tigrinum) and boreal chorus frogs (Pseudacris maculate) were found in the area and the article suggests the possibility that the fungus may have been transmitted to the terrestrial salamander through direct or indirect contact with an infected aquatic amphibian. Muletz et al. (2014) found no Bd on preserved Plethodon spp. from the Appalachian Mountains and an extremely low incidence in wild specimens and concluded that these exceptionally low levels of Bd, in a region known to harbor Bd, may indicate that Plethodon specific traits limit Bd infection. Amphibian species known to acquire the disease inhabit areas within P. stormi range creating a potential mode of transport.

A new emerging chytrid fungus, B. salamandrivorans (Bsal), has resulted in large-scale declines of some wild populations of salamanders in Europe. Martel et al. (2014) assessed 24 species of salamanders from 5 families and found that species from the families Salamandridae and Plethodontidae, particularly newts (family Salamandridae), were found to be the most susceptible to the disease. Only one species in genus Plethodon was included in the susceptibility tests, P. glutinosus, which incurred transient lesions but was considered “resistant” to the disease. Because this species was infected temporarily, it is considered at least a short-term carrier, and as a result, the USFWS included all Plethodon spp. in its salamander importation ban. To date, there are no documented cases of Bsal in the United States.

CDFW has determined chytridiomycosis is not likely a threat to P. stormi. As water is the primary mode of transmittal for the disease, the terrestrial nature of P. stormi greatly reduces its risk of infection and, if an infection were to occur, the outcome is currently unknown. However, potential introduction of the disease may also occur through fire suppression activities where water harboring Bd is used.

Climate Change
The petition proposing Federal listing of P. stormi identified climate change, specifically an increase in temperature, as a concern and partial justification for protection under the Federal ESA. The petition hypothesized that climate change may lead to less opportunity for P. stormi to forage and reproduce. Further, since P. stormi exhibits low movement/dispersal, the species is unlikely to simply relocate to more suitable habitat as the climate warms.

The U.S. Environmental Protection Agency (2004) cites the National Academy of Sciences in reporting that “[T]he Earth’s surface temperature has risen by about 1 degree Fahrenheit in the past century, with accelerated warming during the past two decades.” The consequences of this trend could include an increase in the average global surface temperature of 1-4.5°F in the next 50 years. Predicted environmental consequences of this include changes in the geographic range of forests, increases in the frequency of fire and insect outbreaks, changes in the carbon storage function of forests, increased precipitation, and changes in weather patterns (Intergovernmental Panel on Climate Change 2001).

The subterranean microenvironment in which P. stormi spend most of their time is less sensitive to temperature changes than aboveground environments. Changes in vegetation types above ground, rainfall and fire frequency likely pose risks to P. stormi by altering elements of the current habitat conditions. Potential effect mechanisms include canopy modification that changes temperature at the soil surface, changes in the rates of organic input to the talus habitat, and changes in the associated animal community that depends upon these organic inputs.