Truly enigmatic declines in terrestrial salamander populations in Great Smoky Mountains National Park

Abstract

Aim Woodland salamanders (genus: Plethodon) declined synchronously across many protected areas in Eastern North America by the mid‐1980s, but no cause was attributed to these declines. We hypothesized that the rapid, synchronous loss of several populations of many species was consistent with the invasive pathogen Batrachochytrium dendrobatidis ( Bd), and we resurveyed historic sites to search for Bd in current populations. Location Great Smoky Mountains National Park. Methods We surveyed 35 sites 2–4 times between March and November 2009, quantified community composition and abundance of 72 populations of six species and three hybrids of Plethodon salamanders, and collected 665 skin swabs to detect Bd. Results At 22 of the 35 sites, we were unable to find one or more species that were historically present. Plethodon glutinosus and P. teyahalee and their hybrids were less abundant than historically found, P. jordani x metcalfi and P. ventralis were more abundant and the remaining three species fluctuated but showed no net change. Yet, only one of the 665 salamanders was positive for Bd. Main conclusions Declines were not associated with particular localities, but occurred in particular species. We conclude that over collecting, logging, and acid rain are unlikely to have caused these population declines, but we were unable to rule out disease or climate change as contributing factors. Population declines of Plethodon salamanders in the Park are substantial and have persisted for 30 years. Determining the cause and the extent of these declines is important for managing this area of global salamander biodiversity.

Overview of chytrid emergence and impacts on amphibians

“…Declines in populations in terrestrial forest salamanders (Family Plethodontidae: Plethodon) occurred throughout the eastern US in the late 1970s to early 1980s [90], although die-offs were not noted and no definitive cause has been identified. Caruso & Lips [91] resurveyed many of Highton's historic collecting sites and found that occupancy and detection were lower for many species of Plethodon in the Great Smoky Mountain National Park. They resurveyed more species at Highton's historic sites and found that many populations of multiple genera have declined in both occupancy and detection (Caruso et al 2012, unpublished data).…”

Batrachochytrium salamandrivorans sp. nov. causes lethal chytridiomycosis in amphibians

“…Chytridiomycosis is currently considered to be caused by a single species of fungus, Batrachochytrium dendrobatidis, which is the only chytridiomycete taxon known to parasitize vertebrate hosts. However, B. dendrobatidis and other factors known to cause amphibian decline fail to explain several recent amphibian population losses (4,5).…”

Potential change in the distribution of an abundant and wide-ranging forest salamander in a context of climate change

“…Given their physiological requirements, they are generally very sensitive to habitat disturbance (deMaynadier and Hunter 1995). Recently, some studies have reported declining abundance of some plethodontid species in North America (Milanovich et al 2010, Caruso and Lips 2013, Kroschel et al 2014, pointing to climate change as a contributing factor for the observed decline. Other studies have predicted negative effects of climate change on the survival of many salamander species in the northeastern United States (Milanovich et al 2010, Sutton et al 2015 as well as on other amphibian species (Parmesan and Yohe 2003).…”