Demography and space-use of Eastern Red-backed Salamanders (Plethodon cinereus) between mature and successional forests

Abstract

Space-use and demographic processes are critical to the persistence of populations across space and time. Despite their importance, estimates of these processes are often derived from a limited number of populations spanning broad habitat or environmental gradients. With increasing appreciation of the role fine-scale environmental variation in microgeographic adaptation, there is a need and value to assessing within-site variation in space-use and demographic patterns. In this study, we analyze 3 years of spatial capture-recapture data on the Eastern Red-backed Salamander collected from a mixed-use deciduous forest site in central Ohio, USA. Study plots were situated in both a mature forest stand and successional forest stand separated by <100-m distance. Our results showed that salamander density was reduced on successional plots, which corresponded with greater distance between nearest neighbors, less overlap in core use areas, greater space-use, and greater shifts in activity centers when compared to salamanders occupying the mature habitat. By contrast, individual growth rates of salamanders occupying the successional forest were significantly greater than salamanders in the mature forest. These estimates result in successional plot salamanders reaching maturity more than 1 year earlier than salamanders on the mature forest plots and increasing their estimated lifetime fecundity by as much as 43%. The patterns we observed in space-use and individual growth are likely the result of density-dependent processes, potentially reflecting differences in resource availability or quality. Our study highlights how fine-scale, within-site variation can shape population demographics. As research into the demographic and population consequences of climate change and habitat loss and alteration continue, future research should take care to acknowledge the role that fine-scale variation may play, especially for abiotically sensitive organisms with limited vagility.

Keywords: demography; fecundity; fine‐scale; forest; salamander; succession.

FIGURE 1

Map of the study site in Delaware County, Ohio, showing the location of the paired plots in successional (triangles) and mature (circles) forest. Inset images show associated coverboard arrays for each site.

FIGURE 2

Density plot showing the posterior distributions for asymptotic size for male and female Eastern Red‐backed Salamanders, Plethodon cinereus (a) and posterior distributions for the growth coefficient for males and females occupying mature and successional forest plots (b). With greater than 99% probability, all contrasts indicate that males are smaller than females, males grow faster than females, and males and females on the successional forest plots grow faster than males and females on the mature forest plots.

FIGURE 3

Time to maturity plot, indicating the expected time it would take female (a) and male (b) Eastern Red‐backed Salamanders, Plethodon cinereus, to reach sexual maturity (34 mm SVL), given their development in either mature or successional habitats. Starting from a hatching SVL of 13 mm, 50% of juvenile female salamanders occupying successional habitat are expected to reach the minimum size of sexual maturity after 3.30 years compared to 4.30 years for females occupying the mature forest plots (a). By contrast, 50% of males are expected to reach maturity in 2.25 years and 2.75 years in successional and mature forest habitat, respectively (b).

FIGURE 4

Density plot showing the average number of individual Plethodon cinereus that had overlapping core (50% UD) home ranges with each salamander (a) and the average distance between salamander activity centers (b) in mature and successional forest plots. Salamanders occupying mature habitat tended to have more individuals potentially occurring within their core home range than salamanders occupying successional forest habitat, which coincided with less distance between salamanders occupying mature forest plots.