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The sensitivity of amphibian species to shifts in environmental conditions has been exhibited through long-term population studies and the projection of ecological niche models under expected conditions. Species in biodiversity hotspots have been the focus of ample predictive modeling studies, while, despite their significant ecological value, wide-ranging and common taxa have received less attention. We focused on predicting range restriction of the spotted salamander (Ambystoma maculatum), blue-spotted salamander (A. laterale), four-toed salamander (Hemidactylium scutatum), and redbacked salamander (Plethodon cinereus) under future climate scenarios. Using bias-corrected future climate data and biodiversity database records, we developed maximum entropy (MaxEnt) models under current conditions and for climate change projections in 2050 and 2070. We calculated positivity rates of species localities to represent proportions of habitat expected to remain climatically suitable with continued climate change. Models projected under future conditions predicted average positivity rates of 91% (89–93%) for the blue-spotted salamander, 23% (2–41%) for the spotted salamander, 4% (0.7–9%) for the four-toed salamander, and 61% (42–76%) for the red-backed salamander. Range restriction increased with time and greenhouse gas concentration for the spotted salamander, four-toed salamander, and red-backed salamander. Common, widespread taxa that often receive less conservation resources than other species are at risk of experiencing significant losses to their climatic ranges as climate change continues. Efforts to maintain populations of species should be focused on regions expected to experience fewer climatic shifts such as the interior and northern zones of species' distributions.

Non-native earthworms found in Eastern Canada substantially affect soil properties and plant diversity, but less is known about their impacts on higher faunal species. We investigated the effects of non-native earthworms on populations of Plethodon cinereus , a common woodland salamander. We hypothesized that earthworms could adversely affect P. cinereus by consuming the forest floor, thereby decreasing soil moisture and the abundance of native preys. Conversely, earthworms could positively affect P. cinereus by providing refuge in their abandoned burrows and by being a novel prey. We installed 25 coverboards in 38 mature sugar maple ( Acer saccharum ) forests, 24 of which were earthworm-free. Over the next two years, we monitored earthworm and salamander populations using hot mustard extractions and visible implant elastomers, respectively. At a subset of four sites, two with and two without earthworms, we determined salamander diets in the spring (May–June), summer (July–August) and fall (September–October) seasons, using gastric lavage techniques. Forest floor depth decreased, whereas population density, body size and total prey volume of P. cinereus increased, with earthworm abundance. Earthworms, which are soft-bodied and nutritious prey, composed most of the salamander diet at sites with earthworms, volumetrically accounting for > 50% of total prey volume. Despite this, we found fewer prey items in the stomach of salamanders at earthworm-invaded sites, indicating that salamanders are getting a higher caloric intake per feeding while expending less energy. We conclude that non-native earthworms have a net beneficial effect on P. cinereus populations in Eastern Canada, mainly by improving diet quality.

When evolutionarily divergent lineages adjoin their geographic ranges after a period of isolation, myriad outcomes can occur, from population anastomosis to the evolution of reproductive isolation by way of reinforcement. Hybrid zones represent natural experiments that may indicate whether lineages will maintain their evolutionary independence. Here, we report on a hybrid zone in the Eastern Red-Backed Salamander, Plethodon cinereus, a highly abundant and wide-ranging terrestrial salamander found in the northeastern United States and in southeastern Canada. An earlier study identified six distinct mitochondrial clades across the range of P. cinereus. Populations of two of these clades were as close as 9.6 km apart in Lorain County, Ohio, USA. To investigate the nature of this contact zone, we sampled 316 individuals from 16 sites along a 53-km transect, and analyzed 10 microsatellite loci and one mitochondrial locus. We found a clinal transition for mtDNA haplotypes. In contrast, most studies of terrestrial plethodontid salamanders commonly exhibit sharp boundaries between mtDNA clades. Microsatellite markers, however, revealed little differentiation and weak population structure, suggesting the nuclear cline, if it exists, lies outside of our sampling region. Explanations for the discordance between the mitochondrial DNA and our microsatellite data include lineage sorting, male-biased dispersal, or historical introgression of mtDNA, among other possibilities. We compare our results with other studies of introgression in terrestrial salamanders, and discuss the causes of mitonuclear discordance.

Members of the Iridoviridae family, genus Ranavirus, represent a group of globally emerging pathogens of ecological and economic importance. In 2017, an amphibian die-off of wood frogs (Rana sylvatica) and boreal chorus frogs (Pseudacris maculata) was reported in Wood Buffalo National Park, Canada. Isolation and complete genomic sequencing of the tissues of a wood frog revealed the presence of a frog virus 3 (FV3)-like isolate, Rana sylvatica ranavirus (RSR), with a genome size of 105,895 base pairs, 97 predicted open reading frames (ORFs) bearing sequence similarity to FV3 (99.98%) and a FV3-like isolate from a spotted salamander in Maine (SSME; 99.64%). Despite high sequence similarity, RSR had a unique genomic composition containing ORFs specific to either FV3 or SSME. In addition, RSR had a unique 13 amino acid insertion in ORF 49/50L. No differences were found in the in vitro growth kinetics of FV3, SSME, and RSR; however, genomic differences between these isolates were in non-core genes, implicated in nucleic acid metabolism and immune evasion. This study highlights the importance of viral isolation and complete genomic analysis as these not only provide information on ranavirus spatial distribution but may elucidate genomic factors contributing to host tropism and pathogenicity.

Climatic and geological changes in eastern North America have shaped population history and genetic diversity in many taxa. A common finding of phylogeographic investigations is that southern populations exhibit relatively high levels of phylogeographic structure, whereas northern populations, especially those that have invaded postglacial landscapes, exhibit relatively little genetic differentiation. Here, we describe the results of a phylogeographic investigation of Eastern Red-backed Salamander (Plethodon cinereus), a species that is widely distributed throughout the northeastern United States and southeastern Canada, with roughly three quarters of its range north of the southernmost glacial extent during the last glacial maximum. To investigate patterns of genetic variation, we collected genetic samples from 202 individuals from 107 populations from across the range of P. cinereus, with denser sampling in the southern portion of the range. In total, 4486 base pairs (bp) of DNA were sequenced, including three mitochondrial DNA (mtDNA; 2239 bp) loci and three nuclear (2247 bp) loci. A mix of phylogenetic, population genetic, and clustering approaches were used to explore and summarize patterns of genetic variation. Bayesian phylogenetic analysis of mtDNA recovered six well-supported, geographically cohesive clades that increase in geographic range size from south to north, with a most recent common ancestor estimated at 1.49 million years (95% highest posterior density = 1.09–1.95). The northernmost clade possessed a horseshoe-shaped distribution, including the eastern seaboard, all or part of southeastern Canada, and Michigan, Indiana, and Ohio; thus, this clade was recovered south of the last glacial boundary in both the east and the west. Using simple population genetic tests, we showed evidence of range expansion and isolation by distance in most clades. Using the dispersal-extinction-cladogenesis biogeographic model in RevBayes, we inferred the ancestor of P. cinereus to occupy either the Blue Ridge or the Ridge and Valley physiographic province. In contrast to mtDNA, nuclear loci revealed little phylogeographic structure, and cluster analyses using the nuclear data were not well resolved. Finally, we compare our results with published and unpublished allozyme studies, and we identify several distributional and biogeographic questions that emerge from our findings.

Aim: Plethodon dunni and P. vehiculum are sister species with widely overlapping ranges, yet the distribution of P. vehiculum extends almost 400 km farther north than its sister species. We explore Pleistocene réfugiai structure, competition, physiological tolerances and dispersal ability as contributing factors to the range difference between these two species. Location: The Pacific Northwest of North America, including Oregon, Washington and British Columbia – the full range of both species. Methods: We used genetic, environmental and morphological data to test hypotheses that explain this range difference. Genetic data were used to explore range expansion dynamics and population structure. Species distributional models were used to compare current niches to mid-Holocene and Pleistocene distributions. Morphological data were used to assess phenotypic differences between the species and test for evidence of spatial sorting. Results: Both species underwent rapid range expansions since the Pleistocene and share similar population structure. Species distributional models are different in distribution at all times periods between species. The species are significantly different in all morphological measurements taken. Only P. vehiculum shows evidence of spatial sorting. Main conclusions: Physiological tolerance and dispersal ability best explain the distributional difference between these species. Spatial sorting most likely plays a key role in the range expansion of P. vehiculum.

The geology of the Pleistocene, and particularly the Last Glacial Maximum approximately 26.5 ka, is a critical driver of species present-day distributions and levels of genetic diversity in northern regions. Using mitochondrial DNA sequence data, we tested several predictions relating to the postglacial recolonization of the northern United States and southern Canada by Mudpuppies (Necturus maculosus). Our analyses revealed a significant split between western and eastern lineages, with the divide corresponding to the location of the Mississippi River. Our data support the presence of one or more Mississippian glacial refugia, with subsequent expansion and diversification of a western cluster into the upper Midwest and an eastern cluster into the eastern Great Lakes and New England. As predicted in cases of postglacial colonization, each of these clusters contains a single widespread and common haplotype along with numerous low-frequency, closely related haplotypes. Given recent conservation concerns about amphibians in general, and Mudpuppies specifically, we discuss our results in light of species conservation. Knowledge of a species' genetic diversity allows for informed management and facilitates decisions that preserve local adaptation and evolutionary potential.

Mudpuppies (Necturus maculosus) are secretive, fully aquatic salamanders with a range that spans much of the eastern United States and Canada including the Great Lakes region. Although this species was once abundant, there have been widespread declines due to habitat loss and modification, pollution, lampricide use, and overcollection. We compared environmental DNA (eDNA) and trapping surveys conducted from 2014 to 2016 to determine Mudpuppy occupancy along the St. Clair-Detroit River System, where this indicator species could be a gauge for success of ongoing restoration. Mudpuppy eDNA was detected at all sites with positive trapping records, as well as one site where individuals have not been trapped previously. Sites with shoreline restoration had the highest occupancy estimates, whereas deep-water restoration did not affect Mudpuppy occupancy. Additionally, eDNA surveys resulted in higher detection probability than setline and minnow trap survey methods, illustrating the benefit of using eDNA to detect secretive species. This study demonstrates the success of restoration efforts in increasing the occupancy of an indicator species and can be used as a template for other restoration initiatives.

Some 300 species of amphibians inhabit North America. The past two decades have seen an enormous growth in interest about amphibians and an increased intensity of scientific research into their fascinating biology and continent-wide distribution. This atlas presents the spectacular diversity of North American amphibians in a geographic context. It covers all formally recognized amphibian species found in the United States and Canada, many of which are endangered or threatened with extinction. Illustrated with maps and photos, the species accounts provide current information about distribution, habitat, and conservation. Researchers, professional herpetologists, and anyone intrigued by amphibians will value North American Amphibians as a guide and reference.