Equal probability plot for high quality (HQ) microhabitat use when salamanders (<i>Plethodon cinereus</i>) were alone or paired with pheretimoid earthworms.

<p>The diagonal line indicates no difference in a salamander’s HQ zone use when they were alone vs. paired with an earthworm. Points above the line represent salamanders that used the HQ zone more often when alone, while points below the line represent salamanders that used the HQ zone more often when paired with an earthworm.</p

Invasive Asian Earthworms Negatively Impact Keystone Terrestrial Salamanders

<div><p>Asian pheretimoid earthworms (e.g. <i>Amyntha</i>s and <i>Metaphire</i> spp.) are invading North American forests and consuming the vital detrital layer that forest floor biota [including the keystone species <i>Plethodon cinereus</i> (Eastern Red-backed Salamander)], rely on for protection, food, and habitat. <i>Plethodon cinereus</i> population declines have been associated with leaf litter loss following the invasion of several exotic earthworm species, but there have been few studies on the specific interactions between pheretimoid earthworms and <i>P</i>. <i>cinereus</i>. Since some species of large and active pheretimoids spatially overlap with salamanders beneath natural cover objects and in detritus, they may distinctively compound the negative consequences of earthworm-mediated resource degradation by physically disturbing important salamander activities (foraging, mating, and egg brooding). We predicted that earthworms would exclude salamanders from high quality microhabitat, reduce foraging efficiency, and negatively affect salamander fitness. In laboratory trials, salamanders used lower quality microhabitat and consumed fewer flies in the presence of earthworms. In a natural field experiment, conducted on salamander populations from “non-invaded” and “pheretimoid invaded” sites in Ohio, salamanders and earthworms shared cover objects ~60% less than expected. Earthworm abundance was negatively associated with juvenile and male salamander abundance, but had no relationship with female salamander abundance. There was no effect of pheretimoid invasion on salamander body condition. Juvenile and non-resident male salamanders do not hold stable territories centered beneath cover objects such as rocks or logs, which results in reduced access to prey, greater risk of desiccation, and dispersal pressure. Habitat degradation and physical exclusion of salamanders from cover objects may hinder juvenile and male salamander performance, ultimately reducing recruitment and salamander abundance following Asian earthworm invasion.</p></div

A comparison of large pheretimoid earthworm population characteristics [33, 34] at the soil surface and <i>Plethodon cinereus</i> microhabitat occupancy [35] throughout the year in Ohio, USA.

<p>A comparison of large pheretimoid earthworm population characteristics [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151591#pone.0151591.ref033" target="_blank">33</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151591#pone.0151591.ref034" target="_blank">34</a>] at the soil surface and <i>Plethodon cinereus</i> microhabitat occupancy [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151591#pone.0151591.ref035" target="_blank">35</a>] throughout the year in Ohio, USA.</p

The relationship between pheretimoid earthworm and <i>P</i>. <i>cinereus</i> as measured by earthworm abundance and LL score.

<p>Juveniles were significantly associated with earthworm abundance (A) and LL score (D). There was a negative relationship between earthworm and male salamander abundance (B) but no relationship between male salamanders and LL score (E). Female salamanders were neither associated with worm abundance (C) or LL score (F). Asterisks indicate statistically significant results.</p

Ziemba et al. 2016 Lab and Field Data

Laboratory and field data for experiments examining the interactions between invasive Asian earthworms and terrestrial salamanders in northeastern Ohio, USA