Fine-Scale Habitat Associations of a Terrestrial Salamander: The Role of Environmental Gradients and Implications for Population Dynamics

Abstract

Environmental gradients are instrumental in shaping the distribution and local abundance of species because at the most fundamental level, an organism’s performance is constrained by the environment it inhabits. In topographically complex landscapes, slope, aspect, and vegetative cover interact to affect solar exposure, creating temperature-moisture gradients and unique microclimates. The significance of the interaction of abiotic gradients and biotic factors such as competition, movement, or physiology has long been recognized, but the scale at which these factors vary on the landscape has generally precluded their inclusion in spatial abundance models. We used fine-scale spatial data relating to surface-soil moisture, temperature, and canopy cover to describe the spatial distribution of abundance of a terrestrial salamander, Plethodon albagula, across the landscape. Abundance was greatest in dense-canopy ravine habitats with high moisture and low solar exposure, resulting in a patchy distribution of abundance. We hypothesize that these patterns reflect the physiological constraints of Plethodontid salamanders. Furthermore, demographic cohorts were not uniformly distributed among occupied plots on the landscape. The probability of gravid female occurrence was nearly uniform among occupied plots, but juveniles were much more likely to occur on plots with lower surface temperatures. The disconnect between reproductive effort and recruitment suggests that survival differs across the landscape and that local population dynamics vary spatially. Our study demonstrates a connection between abundance, fine-scale environmental gradients, and population dynamics, providing a foundation for future research concerning movement, population connectivity, and physiology.

Effective Use of Trails for Assessing Terrestrial Salamander Abundance and Detection: A Case Study at Great Smoky Mountains National Park

“…For example, Crawford and Semlitsch (2008) found that abundance of plethodontid salamanders was significantly lower in timber stands that had lower leaf litter depths and that diurnal area-constrained surveys for plethodontid salamanders resulted in significantly lower counts when compared to nighttime surveys. Peterman and Semlitsch (2013) found that detection of salamanders during daytime surveys was significantly affected by the amount of searchable cover. Our results suggest transect-level differences in microclimate and habitat altered detection and abundance of terrestrial salamanders at GSMNP (Table 1); however, if microclimate or habitat differences existed across trail or non-trail transects, they did not manifest to measurable differences in detection or abundance of terrestrial salamanders (Table 1).…”

“…Surface activity in plethodontid salamanders is highly variable (Bailey et al 2004c) and may vary in relation to fine-scale habitat features (e.g., Peterman and Semlitsch 2013) or weather at the time of sampling (Connette and Semlitsch 2013;Peterman and Semlitsch 2013). Failure to account for imperfect detection can result in erroneous inference, where observation error occludes accurate estimate of the ecological process of interest (MacKenzie et al 2006;Royle and Dorazio 2008).…”

“…For example, Hyde and Simons (2001) used four different sampling techniques in Great Smoky Mountains National Park (GSMNP) to quantify plethodontid diversity and relative abundance, and found significant variability in salamander counts depending upon the sampling method used and habitat type being surveyed. Further, numerous studies have demonstrated that both individual and population-level detection probability of plethodontid salamanders is almost always less than one (Bailey et al 2004a(Bailey et al , 2004b(Bailey et al , 2004dConnette and Semlitsch 2013;Peterman and Semlitsch 2013). To calculate unbiased abundance estimates and to correctly infer how landscape covariates affect abundance, it is critical to use survey and statistical methods to account for imperfect detection (Royle 2004).…”

Environmental and Anthropogenic Factors Influencing Salamanders in Riparian Forests: A Review

“…For instance, plethodontid salamanders are lungless and rely on cutaneous respiration; to sustain efficient gas exchange, their skin must be kept moist. Therefore, plethodontid salamanders are limited to moist environments and their activity is restricted to periods of high soil moisture [63,77,[104][105][106]. Moisture may furthermore be a factor in the magnitude and timing of annual breeding migrations [69,107].…”

Movement patterns of the cave salamander (Eurycea lucifuga) in Sauerkraut Cave, Kentucky.

“…Cave communities are unique and may be dependent on species like E. lucifuga for nutrient circulation (Petranka 1998). Kentucky and Tennessee contain almost 20% of all the known and accessible karst systems in North America (Barr 1968), and as such increased study and comprehension of the connections between abiotic and biotic factors and cave salamander behavior in local populations could be crucial in understanding the complexities of cave ecosystems across the temperate United States (Davic 2004, Peterman andSemlitsch 2013).…”