Charlie Holguin
Virginia Polytechnic Institute and State University
November 2024
Background
As a result of anthropogenic influences, climate change has led to changes in species ranges and ecological conditions (Velo-Antón et al. 2013). Currently, 41% of amphibians are considered Threatened and approximately 57% of salamanders are listed by the IUCN as Vulnerable, Endangered, or Critically Endangered (IUCN 2022). Salamanders are experiencing increasing temperatures, leading to range shifts, disease outbreaks, reduction of water in breeding sites, and an increased threat of desiccation, which ultimately results in population declines (Wake 1991). This is particularly concerning for salamanders in Southern Appalachia, which is a hotspot for salamander global biodiversity. In this area, the family Plethodontidae represents the highest number species and abundances of salamanders. Due to their lungless physiology, these salamanders are especially vulnerable to climate change and environmental changes. We need to understand life history traits and species demographics to properly manage these species. By investigating salamander dynamics over a 65-year period, I aim to further understand how climate and environmental conditions influence salamander body size and occupancy.
My project has two main goals. First, I will determine if salamander body sizes within 13 species of plethodontid salamanders in southwest Virginia have changed over a 65-year period.
Second, I will analyze historical and contemporary samples of salamander communities along elevation gradients on three mountains in southwestern Viriginia. This project includes historic data housed in the natural history collection at Virginia Tech and The University of Michigan. The data describing salamander species count, body measurements, and environmental data was collected by Dr. Jim Organ (1958–1960) (Organ 1961a, 1961c) and Dr. Kevin Hamed (2008–2013; Unpublished).
Species of Interest
Northern Pygmy Salamander (Desmognathus organi)
Northern Dusky Salamander (Desmognathus fuscus)
Shovel-nosed Salamander (Desmognathus marmoratus)
Seal Salamander (Desmognathus monticola)
Blue Ridge Dusky Salamander (Desmognathus orestes)
Black-bellied Salamander (Desmognathus quadramaculatus)
Blue Ridge Two-lined Salamander (Eurycea wilderae)
Eastern Red-backed Salamander (Plethodon cinereus)
White-spotted Slimy Salamander (Plethodon cylindraceus)
Northern Gray-cheeked Salamander (Plethodon montanus)
Methods
In June 2024, I began resampling three of the ten sites at the Mount Rogers National Recreation Area in Virginia (Whitetop Creek, Dells Branch, Beech Mountain), previously sampled by Drs. James Organ and Kevin Hamed. While sampling each site, we conducted daytime visual encounter surveys to determine salamander presence and detection probability. I also collected species counts, body measurements (snout-vent length and total length), reproductive condition, and environmental data.
Preliminary Findings
The preliminary results suggest that the distribution of some species may be experiencing subtle changes. By comparing data from the 1950s with contemporary data, we are beginning to observe slight changes in distributions. For example, on the southern aspect of Whitetop Mountain, P. welleri was not observed until the final site of the survey (White-Top Creek with an elevation of 5,200 feet), while on the northern aspect, it was found at earlier sites (Dell’s Branch with an elevation of 4,300 feet).
This project is ongoing. Currently, I am in the process of digitizing the historical data. Once the data is digitized, I can start analyzing it to investigate body size trends over the 65-year period. I would also like to continue to sample the remaining sites, adding another 20 years’ worth of data to investigate possible competition and habitat changes. Additionally, if possible, we would like to resample the three sites from this summer to assess any possible changes in the salamander communities due to the damage caused by Hurricane Helen in the Mount Rogers National Recreation Area.
Additional Work
As part of this project, Morgan Crum, a Multicultural Academic Opportunities Program Summer Intern at Virginia Tech, investigated possible mimicry between Desmognathus orestes and Plethodon welleri. She discusses the work below.
This summer, I conducted a research project examining the relationship between the Blue Ridge Dusky (Desmognathus orestes) and Weller’s salamanders (Plethodon welleri), for which Batesian mimicry has been suggested. As a member of the genus Plethodon, P. welleri secretes a noxious substance from its tail as a predator defense. While D. orestes does not share this characteristic, we observed similar dorsal coloration between the two. I collected dorsal color data and images from each species within three sites in the Mount Rogers National Recreation Area. Surveying every 100 feet in elevation gain, ranging from 3000–5200 feet, we sampled more than 600 individuals. Upon analysis, we found statistically significant association of D. orestes with “Weller’s colors” where the two species co-occur at high elevations. I am furthering my analysis through image comparison and creating a reproducible protocol for this comparison to be applicable to other disciplines within the natural sciences.
Literature Cited
IUCN. 2022. The IUCN Red List of Threatened Species. Version 2022-2.
Organ, J. A. 1961b. Studies of the Local Distribution, Life History, and Population Dynamics of the Salamander Genus Desmognathus in Virginia. Ecological Monographs 31:189–220.
Organ, J. A. 1961c. Life History of the Pigmy Salamander, Desmognathus wrighti, in Virginia. The American Midland Naturalist 66:384–390.
McCarthy, T., P. Masson, A. Thieme, P. Leimgruber, and B. Gratwicke. 2017. The relationship between climate and adult body size in redback salamanders (Plethodon cinereus). Geo: Geography and Environment 4:e00031.
Velo-Antón, G., J. L. Parra, G. Parra-Olea, and K. R. Zamudio. 2013. Tracking climate change in a dispersal-limited species: reduced spatial and genetic connectivity in a montane salamander. Molecular Ecology 22:3261–3278.
Wake, D. B. 1991. Declining amphibian populations. Science 253:860.