Long-term occupancy dynamics of the threatened Cheat Mountain salamander and its competitors in relation to linear habitat fragmentation

Abstract

Amphibians are declining globally and while many factors are contributing to this decline, habitat loss and degradation caused by climate and land use changes are among the most critical. Habitat degradation and increased interspecific competition are both concerns for long-term viability of the federally-threatened Cheat Mountain salamander (Plethodon nettingi) which is endemic to high elevations in West Virginia. In this study, we quantified the impacts of linear habitat fragmentation (i.e., a linear forest clearing for creation of a ski slope) on local colonization and extinction probabilities in adjacent forested habitat for the Cheat Mountain salamander and two co-occurring competitor species, eastern red-backed salamander (Plethodon cinereus) and Wehrle’s salamander (Plethodon wehrlei). We also quantified long-term changes in total occupancy of the species within the high elevation study area. We surveyed the salamander community annually from 1988 to 2021 using diurnal natural cover object searches at 43 plots, with 1988 representing three years following linear habitat fragmentation. For each species, we used dynamic occupancy models to identify and model influential covariates for initial occupancy, colonization, extinction, and detection probability. We found that distance to fragmentation was positively correlated with colonization probability for Cheat Mountain salamanders, indicating negative edge effects of the linear forest clearing. Distance to fragmentation was negatively correlated with colonization probability for eastern red-backed salamanders, potentially indicating this species benefited from increased solar radiation or reduced competition from Cheat Mountain salamanders. Predicted occupancy of eastern red-backed salamanders and Wehrle’s salamanders increased over the 34 year monitoring period, indicating potential for increased competitive interactions. Our study suggests that extensive linear habitat fragmentation could result in degraded habitat for Cheat Mountain salamanders in the adjacent forest, and that potential for interactions with competitor species is increasing in high elevation forest stands.