Unexpected Rarity of the Pathogen <i>Batrachochytrium dendrobatidis</i> in Appalachian <i>Plethodon</i> Salamanders: 1957–2011

<div><p>Widespread population declines in terrestrial <i>Plethodon</i> salamanders occurred by the 1980s throughout the Appalachian Mountains, the center of global salamander diversity, with no evident recovery. We tested the hypothesis that the historic introduction and spread of the pathogenic fungus <i>Batrachochytrium dendrobatidis</i> (<i>Bd</i>) into the eastern US was followed by <i>Plethodon</i> population declines. We expected to detect elevated prevalence of <i>Bd</i> prior to population declines as observed for Central American plethodontids. We tested 1,498 <i>Plethodon</i> salamanders of 12 species (892 museum specimens, 606 wild individuals) for the presence of <i>Bd</i>, and tested 94 of those for <i>Batrachochytrium salamandrivorans (Bs)</i> and for ranavirus. Field samples were collected in 2011 from 48 field sites across a 767 km transect. Historic samples from museum specimens were collected at five sites with the greatest number and longest duration of collection (1957–987), four of which were sampled in the field in 2011. None of the museum specimens were positive for <i>Bd</i>, but four <i>P. cinereus</i> from field surveys were positive. The overall <i>Bd</i> prevalence from 1957–2011 for 12 <i>Plethodon</i> species sampled across a 757 km transect was 0.2% (95% CI 0.1–0.7%). All 94 samples were negative for <i>Bs</i> and ranavirus. We conclude that known amphibian pathogens are unlikely causes for declines in these <i>Plethodon</i> populations. Furthermore, these exceptionally low levels of <i>Bd</i>, in a region known to harbor <i>Bd</i>, may indicate that <i>Plethodon</i> specific traits limit <i>Bd</i> infection.</p></div

Results of <i>Bd</i> testing for six protected areas in the Appalachian Mountains.

<p>Results of <i>Bd</i> testing for six protected areas in the Appalachian Mountains.</p

We sampled historic specimens collected at five sites (×), and live salamanders from 48 sites (•).

<p>Sampling sites spanned a geographical range of 767–1,687 m in the Appalachian Mountains. An inset of the US is provided to show the geographic extent.</p