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Paul A. Verrell - One of the best experts on this subject based on the ideXlab platform.
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The courtship behaviour of the spotted dusky salamander, Desmognathus fuscus conanti (Amphibia: Caudata: Plethodontidae)
Journal of Zoology, 1995Co-Authors: Paul A. VerrellAbstract:The courtship behaviour of the North American southern dusky salamander, Desmognathus fuscus conanti (Plethodontidae), is described for the first time. The male is the most active participant, as is typical for caudate amphibians, and much of his behaviour can be understood in terms of orientation to and stimulation (or persuasion) of the female. The latter is largely accomplished by the transfer of courtship pheromones from the male's mental (chin) gland. The orientation and persuasion phases of courtship appear necessary if sperm transfer by means of a spermatophore deposited upon the substratum is to be successful. The courtship of D. fuscus conanti is qualitatively identical to that of D. santeetlah, with which it is sexually compatible in the laboratory and with which it may hybridize in nature. However, a broader comparison of species in the genus Desmognathus reveals that the greatest interspecific differences occur during the orientation and persuasion phases of courtship. A complete understanding of the evolution of courtship behaviour in desmognathine salamanders awaits availability of ethograms for all other taxa and a robust, independent phytogeny for the entire subfamily.
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Courtship behaviour of the salamander Desmognathus imitator (Amphibia: Caudata: Plethodontidae)
Amphibia-Reptilia, 1994Co-Authors: Paul A. VerrellAbstract:Courtship in the imitator salamander, Desmognathus imitator, follows a predictable course that appears characteristic for the genus. Three more-or-less consecutive phases are recognized: orientation of the male to the female, persuasion of the female by the male (involving both tactile and chemical stimuli) and indirect sperm transfer by means of a spermatophore. The individual behaviour patterns that comprise courtship in D. imitator are similar to those observed for congeneric species of similar body size, except for "bite-and-seize", which has previously been described only in two dwarf species. Understanding the evolution of courtship in the genus Desmognathus will be greatly facilitated when behavioural characters in all taxa can be optimized onto an independent phylogenetic tree.
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Divergence of mate recognition systems among conspecific populations of the plethodontid salamander Desmognathus santeetlah (Amphibia: Plethodontidae)
Biological Journal of the Linnean Society, 1993Co-Authors: Esther Maksymovitch, Paul A. VerrellAbstract:The disjunct geographic distribution of plethodontid salamanders of the genus Desmognathus provides excellent opportunities to test whether populations diverge in mate recognition systems so as to result in sexual incompatibility. Previous work has shown that sexual incompatibility may exist both among conspecific populations and between different species in this genus. Populations of the Santeetlah dusky salamander, Desmognathus santeetlah, are found at higher elevations in three mountain ranges in the southern Appalachian Mountains of eastern North America, where they are sympatric with congeneric species of similar body size. We report that statistically significant levels of sexual incompatibility exist among populations of D. santeetlah collected from across the species' range. Contrary to popular belief, but in accord with a growing body of empirical literature, aspects of mate recognition systems can diverge among conspecific populations of salamanders, resulting in incidental sexual incompatibility.
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INSEMINATION TEMPORARILY INHIBITS SEXUAL RESPONSIVENESS IN FEMALE SALAMANDERS (Desmognathus OCHROPHAEUS)
Behaviour, 1991Co-Authors: Paul A. VerrellAbstract:After successful courtship and mating in the mountain dusky salamander (Desmognathus ochrophaeus), sperm masses remained externally visible in the cloacae of females for as long as 24 h (Experiment 1). When mated females were exposed to males for a second time, they appeared to be attractive and were subjected to courtship, but they seldom became inseminated (Experiment 2). Courtship and mating appear to result in a temporary inhibition of female sexual responsiveness. Females whose sperm masses were removed on the morning following successful insemination were more likely to become inseminated during a second encounter than were females whose masses were left in situ (Experiment 3). This suggests that it is the presence of a sperm mass, not simply exposure to stimulation produced by males during courtship, that inhibits female sexual responsiveness. In Experiment 4, a small styrofoam ball was placed into the cloacae of females with no recent courtship experience. When paired with males, females bearing "surrogate" sperm masses exhibited lowered courtship frequencies similar to those of recently-mated females, suggesting that physical stimulation of the female cloaca is sufficient to inhibit female sexual responsiveness. Subtle manipulation of female sexual responsiveness by males probably does not occur in Desmognathus ochrophaeus.
Stephen G. Tilley - One of the best experts on this subject based on the ideXlab platform.
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Failed species, innominate forms, and the vain search for species limits: cryptic diversity in dusky salamanders (Desmognathus) of eastern Tennessee
Ecology and Evolution, 2013Co-Authors: Stephen G. Tilley, Renée L. Eriksen, Laura A. Katz, Joseph Bernardo, Lizmarie López, J. Devon Roll, Justin D Kratovil, Noëlle K. J. Bittner, Keith A. CrandallAbstract:Cytochrome B sequences and allozymes reveal complex patterns of molecular variation in dusky salamander (Desmognathus) populations in eastern Tennessee. One group of allozymically distinctive populations, which we refer to as the Sinking Creek form (SCF), combines morphological attributes of Desmognathus fuscus with cytB sequences characteristic of Desmognathus carolinensis. This form is abruptly replaced by D. fuscus just north of Johnson City, TN with no evidence of either sympatry or gene exchange. To the south, allozymic markers indicate a broad zone of admixture with populations characterized by distinct cytB sequences and that may or may not be ultimately referable to Desmognathus conanti. A third distinctive group of populations, which we refer to as the Lemon Gap form (LGF), occurs in the foothills of the Great Smoky and southern Bald Mountains and exchanges genes with Desmognathus santeetlah along the escarpment of the Great Smokies, D. carolinensis in the southern Bald Mountains, and populations of a different haplotype clade in the Ridge and Valley. We treat all these as innominate forms that may represent “failed species,” recognizing that it may never be possible to reconcile species limits with patterns of phylogeny, morphology, and gene exchange in these salamanders.
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Systematics of dusky salamanders, Desmognathus (Caudata: Plethodontidae), in the mountain and Piedmont regions of Virginia and North Carolina, USA
Zoological Journal of the Linnean Society, 2008Co-Authors: Stephen G. Tilley, Renée L. Eriksen, Laura A. KatzAbstract:We analysed mitochondrial (cytochrome b) nucleotide sequences, nuclear allozyme markers, and morphometric characters to investigate species boundaries and phylogenetic relationships among dusky salamanders (Desmognathus) in the southern Blue Ridge and adjacent Piedmont Physiographic Provinces of Virginia and North Carolina. Our results revealed four distinct mitochondrial DNA clades that are also characterized by distinct allozyme markers. One clade consists of sequences derived from populations distributed from New England to south-western Virginia that are referable to Desmognathus fuscus Rafinesque, 1820, although there is considerable sequence and allozyme divergence within this clade. A second clade consists of sequences derived from populations referable to Desmognathus planiceps Newman, 1955, a form that we resurrect from its long synonymy under D. fuscus. Desmognathus planiceps and D. fuscus also differ in mandibular tooth shape. Two other cytochrome b sequences recovered from populations along the Blue Ridge escarpment in southern Virginia are quite divergent from those of the previous two clades, and these populations may represent yet another distinct species. Sequences from a population in the Brushy Mountains in the Piedmont of northern North Carolina are similar to those of Desmognathus carolinensis. Population groupings indicated by allozyme data generally correspond to the cytochrome b clades. Cryptic diversity in Appalachian desmognathan salamanders clearly requires further study. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 152, 115‐130. ADDITIONAL KEYWORDS: allozymes ‐ cytochrome b ‐ Desmognathus planiceps ‐ mitochondrial DNA ‐ morphometrics ‐ phylogeography ‐ taxonomy.
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SYSTEMATICS OF THE Desmognathus OCHROPHAEUS COMPLEX IN THE CUMBERLAND PLATEAU OF TENNESSEE
Herpetological Monographs, 2003Co-Authors: Jennifer A. Anderson, Stephen G. TilleyAbstract:Abstract We attempted to identify salamanders from the Cumberland Plateau of Tennessee that have been referred by previous investigators to Desmognathus ochrophaeus. We compared variation at 22 allozyme loci in 10 populations to allozymic variation in other desmognathines. Multidimensional scaling, cluster, and parsimony analyses indicate that populations from our southernmost localities in the plateau are referable to D. ocoee, whereas the northernmost populations are D. ochrophaeus. In contrast, animals sampled from the middle of the plateau are genetically very distinct from all members of the complex and represent a new species described herein as Desmognathus abditus. D. abditus exhibits very limited gene exchange with D. ocoee and D. ochrophaeus where it contacts those forms. A population from the Eastern Highland Rim that has previously been referred to D. ochrophaeus may represent yet another undescribed species. The southern Cumberland Plateau clearly represents an area of substantial desmognathi...
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The Systematics of Desmognathus Imitator
The Biology of Plethodontid Salamanders, 2000Co-Authors: Stephen G. TilleyAbstract:Desmognathus imitator was originally described, as Desmognathus fuscus imitator, by Dunn (1927). Dunn correctly perceived that two correlated color pattern characters, chromatic cheek patches and wavy dorsolateral stripes, distinguish D. imitator from other sympatric desmognathines. The species was subsequently placed in synonymy under Desmognathus fuscus carolinensis by Pope (1928), who believed that red-cheeked Desmognathus from the Great Smokies and elsewhere in the southern Appalachians represented color morphs of that form. Desmognathus imitator owes its rescue from synonymy to Richard Highton, whose decision to include a series of Desmognathus from Siler’s Bald in the Great Smoky Mountains on his Plethodon blood protein gels revealed that two reproductively isolated forms of the Desmognathus ochrophaeus complex inhabit that locality. Subsequent electrophoretic analyses (Tilley et al., 1978) revealed that one of these distinct species was clearly the form described by Dunn (1927), and that D. imitator is endemic to the Great Smoky and adjacent parts of the Great Balsam Mountains. The other member of the Desmognathus ochrophaeus complex with which D. imitator is sympatric is now referred to Desmognathus ocoee Nicholls (Tilley and Mahoney, 1996).
Richard C. Bruce - One of the best experts on this subject based on the ideXlab platform.
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Community Assembly in the Salamander Genus Desmognathus
Herpetological Monographs, 2011Co-Authors: Richard C. BruceAbstract:Abstract In this paper, I present a model of community assembly in the salamander genus Desmognathus based on a survey of assemblage composition throughout the range of the genus. The 21 species of Desmognathus can be sorted into three life-history categories, namely, stream, streamside, and forest, based on duration of the larval phase and a suite of other life-history and morphological traits that are correlated with habitat use of the several life-history stages. In most assemblages having all three life-history categories, stream species are larger than streamside species, and the latter species are larger than forest species. An evaluation of the literature on interspecific competition and predation (i.e., intraguild predation) in Desmognathus indicates that these processes are important in structuring assemblages of these salamanders. Thus, niche assembly, as opposed to dispersal assembly (i.e., neutral model), seems to be a valid model of community assembly in Desmognathus. Only streamside species ...
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Life-History Contributions to Miniaturization in the Salamander Genus Desmognathus (Urodela: Plethodontidae)
Copeia, 2009Co-Authors: Richard C. BruceAbstract:Abstract I investigated the contributions of several life-history traits to small body size in the two smallest species of the genus Desmognathus, D. aeneus and D. wrighti. The research was conducted in the southern Nantahala Mountains of western North Carolina, where the two species co-occur and are similar in body size and life history. Desmognathus ocoee, the next-smallest species in the local Desmognathus assemblage of six species, served as a reference species. All three species have similar juvenile growth rates. Desmognathus aeneus and D. wrighti have smaller propagule sizes (i.e., egg and hatching sizes) and higher developmental rates to sexual maturation than D. ocoee. These two factors, especially the latter, appear to explain much of the difference in adult size between D. ocoee and both D. aeneus and D. wrighti. Thus, miniaturization in D. aeneus and D. wrighti may be mainly a product of acceleration in developmental rate. I suggest that body size itself, rather than other, correlated life-his...
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Out of the frying pan into the fire: an ecological perspective on evolutionary reversal in life history in plethodontid salamanders (Amphibia: Plethodontidae)
Evolutionary Ecology, 2007Co-Authors: Richard C. BruceAbstract:I review and analyze interaction webs involving competition and predation in ensembles of plethodontid salamanders in the southern Appalachian Mountains, USA. The objective is to evaluate hypotheses on interaction webs and population regulation in these ensembles in the context of traditional and recent models of phylogeny and life-history evolution of plethodontids. Two ecological hypotheses evaluated are (1) Hairston’s conjecture on differences in the kinds of interactions prevalent among biphasic species with an aquatic larval stage, versus terrestrial species with direct development; and (2) Grover’s hypothesis on differences in the factors that limit the distribution of species along the moisture gradient from stream to forest. An evolutionary question concerns the supposition derived from recent phylogenetic reconstructions that the history of one major clade, the supergenus Desmognathus , involved an early transition or reversal from a simple life cycle (direct development) to a biphasic life cycle (larval development, metamorphosis), and that this transition promoted the subsequent adaptive radiation of the taxon. Chippindale et al. proposed that selection for life-history reversal in the genus Desmognathus was promoted by competition between direct-developing ancestral desmognathans and other terrestrial plethodontids. Experimental studies of interaction webs in extant ensembles of plethodontids in the southern Appalachians, in concert with data from descriptive studies of feeding and habitat use, demonstrate variation in the relative importance of competition and predation in population regulation of species in the several codistributed lineages of these salamanders. Whereas the existing ecological data do not refute the Chippindale et al. hypothesis, many unresolved questions require additional investigation.
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Population Structure and Life History Attributes of Syntopic Populations of the Salamanders Desmognathus aeneus and Desmognathus wrighti (Amphibia: Plethodontidae)
Southeastern Naturalist, 2005Co-Authors: Kevin J. Hining, Richard C. BruceAbstract:Abstract We investigated population structure and life history traits in syntopic populations of Desmognathus aeneus and Desmognathus wrighti in the southern Nantahala Mountains, NC. The two species occupy similar microhabitats in the spring months, occurring in clumps of moss and damp leaf litter and under stones and logs in deciduous forests bordering streams and seepages. We examined the reproductive organs in living individuals taken in large samples in early spring. The goal was to determine sex and reproductive status. We confirmed these assessments by dissections of small numbers of preserved individuals collected in the same months of later years. The sample of D. wrighti included first-year juveniles (8 mo), second-year juveniles and adult males (20 mo), and third-year and older adults (≥ 32 mo). Similarly, the sample of D. aeneus contained first-year (11 mo), second-year (23 mo), and third-year and older (≥ 35 mo) individuals, in the same reproductive categories as identified in D. wrighti. The ...
David A. Beamer - One of the best experts on this subject based on the ideXlab platform.
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Towards rectifying limitations on species delineation in dusky salamanders (Desmognathus: Plethodontidae): An ecoregion-drainage sampling grid reveals additional cryptic clades.
Zootaxa, 2020Co-Authors: David A. Beamer, Trip LambAbstract:Dusky salamanders (Desmognathus) constitute a large, species-rich group within the family Plethodontidae, and though their systematic relationships have been addressed extensively, most studies have centered on particular species complexes and therefore offer only piecemeal phylogenetic perspective on the genus. Recent work has revealed Desmognathus to be far more clade rich-35 reciprocally monophyletic clades versus 22 recognized species-than previously imagined, results that, in turn, provide impetus for additional survey effort within clades and across geographic areas thus far sparsely sampled. We conceived and implemented a sampling regime combining level IV ecoregions and independent river drainages to yield a geographic grid for comprehensive recovery of all genealogically exclusive clades. We sampled over 550 populations throughout the distribution of Desmognathus in the eastern United States of America and generated mitochondrial DNA sequence data (mtDNA; 1,991 bp) for 536 specimens. A Bayesian phylogenetic reconstruction of the resulting haplotypes revealed forty-five reciprocally monophyletic clades, eleven of which have never been included in a comprehensive phylogenetic reconstruction, and an additional three not represented in any molecular systematic survey. Although general limitations associated with mtDNA data preclude new species delineation, we profile each of the 45 clades and assign names to 10 new clades (following a protocol for previous clade nomenclature). We also redefine several species complexes and erect new informal species complexes. Our dataset, which contains topotypic samples for nearly every currently recognized species and most synonymies, will offer a robust framework for future efforts to delimit species within Desmognathus.
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Phylogenomic data reveal reticulation and incongruence among mitochondrial candidate species in Dusky Salamanders (Desmognathus)
Molecular phylogenetics and evolution, 2020Co-Authors: R. Alexander Pyron, Kyle A. O'connell, Emily Moriarty Lemmon, Alan R. Lemmon, David A. BeamerAbstract:Abstract Gene flow between evolutionarily distinct lineages is increasingly recognized as a common occurrence. Such processes distort our ability to diagnose and delimit species, as well as confound attempts to estimate phylogenetic relationships. A conspicuous example is Dusky Salamanders (Desmognathus), a common model-system for ecology, evolution, and behavior. Only 22 species are described, 7 in the last 40 years. However, mitochondrial datasets indicate the presence of up to 45 “candidate species” and multiple paraphyletic taxa presenting a complex history of reticulation. Some authors have even suggested that the search for species boundaries in the group may be in vain. Here, we analyze nuclear and mitochondrial data containing 161 individuals from at least 49 distinct evolutionary lineages that we treat as candidate species. Concatenated and species-tree methods do not estimate fully resolved relationships among these taxa. Comparing topologies and applying methods for estimating phylogenetic networks, we find strong support for numerous instances of hybridization throughout the history of the group. We suggest that these processes may be more common than previously thought across the phylogeography-phylogenetics continuum, and that while the search for species boundaries in Desmognathus may not be in vain, it will be complicated by factors such as crypsis, parallelism, and gene-flow.
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Dusky salamanders (Desmognathus, Plethodontidae) from the Coastal Plain: Multiple independent lineages and their bearing on the molecular phylogeny of the genus
Molecular phylogenetics and evolution, 2008Co-Authors: David A. Beamer, Trip LambAbstract:Recent phylogenetic reassessment of the lungless salamanders (Plethodontidae) confirmed a major life-history reversal—from direct development to an aquatic larval stage—in the dusky salamanders (Desmognathus) of eastern North America. This reversal initiated high rates of lineage accumulation, reputedly generating the species richness and ecological breath that now characterize Desmognathus. Certain important aspects of the radiation, e.g., ecomorphological evolution, have been identified through intense sampling effort of Appalachian Highland lineages. However, the research preoccupation on montane species has left overlooked a significant component of dusky salamander distribution—the Coastal Plain. We present the first molecular phylogeny for Desmognathus to incorporate extensive coverage from the Atlantic and Gulf coastal plains. We examined 38 Coastal Plain populations in conjunction with 45 additional populations, representing 16 of the 19 nominal species. Bayesian analysis of 88 mitochondrial cox1 haplotypes diagnosed eight independent population lineages within the Coastal Plain, a number at odds with the region’s three currently recognized species. Desmognathus has apparently experienced a complex biogeographic history in this physiographic region, one involving multiple invasions and several ecological transitions from lotic to lentic habitats. 2008 Elsevier Inc. All rights reserved.
Laura A. Katz - One of the best experts on this subject based on the ideXlab platform.
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Failed species, innominate forms, and the vain search for species limits: cryptic diversity in dusky salamanders (Desmognathus) of eastern Tennessee
Ecology and Evolution, 2013Co-Authors: Stephen G. Tilley, Renée L. Eriksen, Laura A. Katz, Joseph Bernardo, Lizmarie López, J. Devon Roll, Justin D Kratovil, Noëlle K. J. Bittner, Keith A. CrandallAbstract:Cytochrome B sequences and allozymes reveal complex patterns of molecular variation in dusky salamander (Desmognathus) populations in eastern Tennessee. One group of allozymically distinctive populations, which we refer to as the Sinking Creek form (SCF), combines morphological attributes of Desmognathus fuscus with cytB sequences characteristic of Desmognathus carolinensis. This form is abruptly replaced by D. fuscus just north of Johnson City, TN with no evidence of either sympatry or gene exchange. To the south, allozymic markers indicate a broad zone of admixture with populations characterized by distinct cytB sequences and that may or may not be ultimately referable to Desmognathus conanti. A third distinctive group of populations, which we refer to as the Lemon Gap form (LGF), occurs in the foothills of the Great Smoky and southern Bald Mountains and exchanges genes with Desmognathus santeetlah along the escarpment of the Great Smokies, D. carolinensis in the southern Bald Mountains, and populations of a different haplotype clade in the Ridge and Valley. We treat all these as innominate forms that may represent “failed species,” recognizing that it may never be possible to reconcile species limits with patterns of phylogeny, morphology, and gene exchange in these salamanders.
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Systematics of dusky salamanders, Desmognathus (Caudata: Plethodontidae), in the mountain and Piedmont regions of Virginia and North Carolina, USA
Zoological Journal of the Linnean Society, 2008Co-Authors: Stephen G. Tilley, Renée L. Eriksen, Laura A. KatzAbstract:We analysed mitochondrial (cytochrome b) nucleotide sequences, nuclear allozyme markers, and morphometric characters to investigate species boundaries and phylogenetic relationships among dusky salamanders (Desmognathus) in the southern Blue Ridge and adjacent Piedmont Physiographic Provinces of Virginia and North Carolina. Our results revealed four distinct mitochondrial DNA clades that are also characterized by distinct allozyme markers. One clade consists of sequences derived from populations distributed from New England to south-western Virginia that are referable to Desmognathus fuscus Rafinesque, 1820, although there is considerable sequence and allozyme divergence within this clade. A second clade consists of sequences derived from populations referable to Desmognathus planiceps Newman, 1955, a form that we resurrect from its long synonymy under D. fuscus. Desmognathus planiceps and D. fuscus also differ in mandibular tooth shape. Two other cytochrome b sequences recovered from populations along the Blue Ridge escarpment in southern Virginia are quite divergent from those of the previous two clades, and these populations may represent yet another distinct species. Sequences from a population in the Brushy Mountains in the Piedmont of northern North Carolina are similar to those of Desmognathus carolinensis. Population groupings indicated by allozyme data generally correspond to the cytochrome b clades. Cryptic diversity in Appalachian desmognathan salamanders clearly requires further study. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 152, 115‐130. ADDITIONAL KEYWORDS: allozymes ‐ cytochrome b ‐ Desmognathus planiceps ‐ mitochondrial DNA ‐ morphometrics ‐ phylogeography ‐ taxonomy.