Unexpected spatial population ecology of a widespread terrestrial salamander near its southern range edge

Abstract

Under the current amphibian biodiversity crisis, common species provide an opportunity to measure population dynamics across a wide range of environmental conditions while examining the processes that determine abundance and structure geographical ranges. Studying species at their range limits also provides a window for understanding the dynamics expected in future environments under increasing climate change and human modification. We quantified patterns of seasonal activity, density and space use in the eastern red-backed salamander ( Plethodon cinereus ) near its southern range edge and compare the spatial ecology of this population to previous findings from the core of their range. This southern population shows the expected phenology of surface activity based on temperature limitations in warmer climates, yet maintains unexpectedly high densities and large home ranges during the active season. Our study suggests that ecological factors known to strongly affect amphibian populations (e.g. warm temperature and forest fragmentation) do not necessarily constrain this southern population. Our study highlights the utility of studying a common amphibian as a model system for investigating population processes in environments under strong selective pressure.

Demographic consequences of changing body size in a terrestrial salamander

“…This species of terrestrial salamander is particularly widespread and can be found as far north as Quebec and as far south as North Carolina (Petranka, 1998). Southern populations of red‐backed salamanders exhibit seasonal periods of surface activity separated by a long period of surface inactivity during the summer months where individuals retreat to underground refugia to decrease risk of desiccation (Hernández‐Pacheco et al., 2019; Nagel, 1977). This salamander is a dispersal‐limited species with narrow space use of <5 m and mean maximum movement distance ranging from 0.7 to 1.9 m (Hernández‐Pacheco et al., 2019; Muñoz et al., 2016; Sutherland et al., 2016).…”

“…Each array consisted of 50 pine cover boards (30.5 × 30.5 × 2.1 cm) spaced 1 m apart in a rectangular grid (Sutherland et al., 2016). Each cover board served as an “open trap” that was surveyed on multiple capture occasions in two field seasons defined by availability for capture on the surface (season 1: autumn 2016–spring 2017; season 2: autumn 2017–spring 2018; Hernández‐Pacheco et al., 2019). During field season 1, we surveyed Sites 1, 2, and 3 on 6 capture occasions.…”

“…We also estimated annual number of eggs per female for each field seasons. As individuals were captured in three different sites, we accounted for spatial heterogeneity by including a site effect on all parameters (Hernández‐Pacheco et al., 2019). However, we did not include movement among sites because this salamander is a dispersal‐limited species and plots are situated far apart to avoid migration (Hernández‐Pacheco et al., 2019).…”

“…We first estimated monthly average mortality hazard rate H (Ergon et al., 2018) to model the probability that individuals survive between each capture occasion. We used the likelihood of a Cormack–Jolly–Seber (CJS) model to analyze monthly apparent survival S m and recapture p probabilities based on previous analysis of this population (Hernández‐Pacheco et al., 2019). We used a log‐log link to model monthly apparent survival and a logit link to model recapture probability.…”

Genetic variation in Plethodon cinereus and Plethodon hubrichti from in and around a contact zone

“…Interestingly, clades of Plethodon typically include species that are very widespread and abundant, but also range‐restricted endemics with among the smallest ranges of any vertebrates in mainland North America (Highton, 1995). Plethodon cinereus , the Eastern Red‐backed Salamander, can reach densities of 2–3 individuals per m 2 across large areas of Eastern North America from North Carolina to central Quebec (Hernández‐Pacheco, Sutherland, Thompson, & Grayson, 2019; Mathis, 1991; Figure 1a). In contrast, narrowly distributed endemics within this group are often species of conservation concern.…”