The Experts below are selected from a list of 1869 Experts worldwide ranked by ideXlab platform
Richard Highton - One of the best experts on this subject based on the ideXlab platform.
-
GEOGRAPHIC PROTEIN VARIATION AND DIVERGENCE IN THE SALAMANDERS OF THE Plethodon WELLERI GROUP (AMPHIBIA, PlethodonTIDAE)
2016Co-Authors: Allan Larson, Richard HightonAbstract:in 26 loci coding for the production of protein products is analyzed in three populations of Plethodon welleri and in 26 populations of Plethodon dorsalis. Protein variation patterns are not consistent with the variation of morphological characters upon which the taxonomic status of these populations has been evaluated. The taxonomic division of P. welleri into subspecies is inconsistent with the electrophoretic data. P. dorsalis includes two groups of populations whose electrophoretic divergence is greater than that observed in any species previously studied. They do not correspond with previously recognized subspecies. Measures of genetic identity (Nei's /) and of population subdivision (Wright's FST) indicate that P. dorsalis is divided into a number of genetically isolated units. The FST values reported for this species are greater than any such values reported previously. It is suggested that the taxonomic recognition of species denotes the presence of a highly canalized phenotype which has been maintained over genetically diverse populations, rather than the genetically homogeneous units of other vertebrate species. Morphological divergence appears to be unrelated to the amount of electrophoretically detected genetic differentiation occurring among populations of the P. welleri group. [Electrophoresis; geographic variation; Amphibia; Plethodontidae.
-
Concurrent speciation in the eastern woodland salamanders (Genus Plethodon): DNA sequences of the complete albumin nuclear and partial mitochondrial 12s genes.
Molecular phylogenetics and evolution, 2012Co-Authors: Richard Highton, Amy Picard Hastings, Catherine A. Palmer, Richard A. Watts, Carla Ann Hass, Melanie Culver, Stevan J ArnoldAbstract:Salamanders of the North American Plethodontid genus Plethodon are important model organisms in a variety of studies that depend on a phylogenetic framework (e.g., chemical communication, ecological competition, life histories, hybridization, and speciation), and consequently their systematics has been intensively investigated over several decades. Nevertheless, we lack a synthesis of relationships among the species. In the analyses reported here we use new DNA sequence data from the complete nuclear albumin gene (1818 bp) and the 12s mitochondrial gene (355 bp), as well as published data for four other genes (Wiens et al., 2006), up to a total of 6989 bp, to infer relationships. We relate these results to past systematic work based on morphology, allozymes, and DNA sequences. Although basal relationships show a strong consensus across studies, many terminal relationships remain in flux despite substantial sequencing and other molecular and morphological studies. This systematic instability appears to be a consequence of contemporaneous bursts of speciation in the late Miocene and Pliocene, yielding many closely related extant species in each of the four eastern species groups. Therefore we conclude that many relationships are likely to remain poorly resolved in the face of additional sequencing efforts. On the other hand, the current classification of the 45 eastern species into four species groups is supported. The Plethodon cinereus group (10 species) is the sister group to the clade comprising the other three groups, but these latter groups (Plethodon glutinosus [28 species], Plethodon welleri [5 species], and Plethodon wehrlei [2 species]) probably diverged from each other at approximately the same time.
-
phylogenetic relationships of the endangered shenandoah salamander Plethodon shenandoah and other salamanders of the Plethodon cinereus group caudata Plethodontidae
Journal of Herpetology, 2004Co-Authors: Jack W Sites, Richard Highton, Mariana Morando, Fred Huber, Robin E JungAbstract:The Shenandoah Salamander (Plethodon shenandoah), known from isolated talus slopes on three of the highest mountains in Shenandoah National Park, is listed as state-endangered in Virginia and federally endangered under the U.S. Endangered Species Act. A 1999 paper by G. R. Thurow described P. shenandoah-like salamanders from three localities further south in the Blue Ridge Physiographic Province, which, if confirmed, would represent a range extension for P. shenandoah of approximately 90 km from its nearest known locality. Samples collected from two of these three localities were included in a molecular phylogenetic study of the known populations of P. shenandoah, and all other recognized species in the Plethodon cinereus group, using a 792 bp region of the mitochondrial cytochrome-b gene. Phylogenetic estimates were based on Bayesian, maximum likelihood, and maximum parsimony methods and topologies examined for placement of the new P. shenandoah-like samples relative to all others. All topologies recovered all haplotypes of the P. shenandoah-like animals nested within P. cinereus, and a statistical comparison of the best likelihood tree topology with one with an enforced (Thurow 1 Shenandoah P. shenandoah) clade revealed that the unconstrained tree had a significantly lower -ln L score (P < 0.05, using the Shimodaira- Hasegawa test) than the constraint tree. This result and other anecdotal information give us no solid reason to consider the Thurow report valid. The current recovery program for P. shenandoah should remain focused on populations in Shenandoah National Park.
-
geographic protein variation and speciation in salamanders of the Plethodon jordani and Plethodon glutinosus complexes in the southern appalachian mountains with the description of four new species
2000Co-Authors: Richard Highton, Robert B PeabodyAbstract:The purpose of this paper is to analyze geographic protein variation in two closely related complexes of southern Appalachian woodland salamanders. The Plethodon jordani complex is restricted to the southern Appalachian Mountains, and the P glutinosus complex is widely distributed in the eastern and central United States. When we began our allozyme studies on eastern Plethodon, both complexes were regarded as monophyletic and each was made the subject of a separate study. Each complex previously had been recognized as a single variable species, Plethodon glutinosus (Green,1818), and Plethodon jordani Blatchley (1901) (Hairston,1950; Highton,1962, Highton,1970, Highton,1972). Highton and MacGregor(1983) and Highton (1984, 1989), showed that there are 16 genetically divergent groups within the P. glutinosus complex and all were recognized taxonomically as separate species. Seven of these occur in the southern Appalachians and three, P. aureolus (Highton 1984); P. glutinosus, and P. teyahalee Hairston (1950), are sympatric at a site in Polk County, Tennessee, without evidence of hybridation (Highton 1984). Both complexes are geographically variable in coloration and size but most individuals are easily identified. Members of the P. glutinosus complex are characterized by the possession of dorsal white or brassy spotting (except in P. chattahoochee) and lateral white or yellow spotting. Salamanders of the P. jordani complex are characterized by usually lacking dorsal spotting, and, except for two groups, most populations lack lateral spotting.
-
geographic protein variation and speciation in the Plethodon dorsalis complex
1997Co-Authors: Richard HightonAbstract:In an analysis of protein variation among geographic populations of the zig-zag sal- amander, Plethodon dorsalis, Larson and Highton found that the amount of genetic divergence is much greater than occurs within most other species of Plethodon. A re-examination of patterns of genetic variation in P. dorsalis indicates that the three most divergent groups should be recognized as different species. Plethodon dorsalis ranges from Illinois and Indiana south to northern and western Kentucky and western Tennessee. Plethodon ventralis sp. nov. ranges from south-central Kentucky, southwestern Virginia, and eastern Tennessee south to northwestern Georgia, northern Alabama, and northeastern Mississippi. Plethodon angusticlavius is found in the Ozark Mountains of Arkansas, Oklahoma, and Missouri. A transect through a contact zone between P dorsalis and P. ventralis in Lincoln County, Kentucky, indicates that there is a narrow hybrid zone <13 km in width between the two species. There is concordant variation in four diagnostic allozyme loci through the hybrid zone, and hybrid populations are genetically more variable than populations of P dorsalis and P ventralis on either side of the hybrid zone.
Allan Larson - One of the best experts on this subject based on the ideXlab platform.
-
GEOGRAPHIC PROTEIN VARIATION AND DIVERGENCE IN THE SALAMANDERS OF THE Plethodon WELLERI GROUP (AMPHIBIA, PlethodonTIDAE)
2016Co-Authors: Allan Larson, Richard HightonAbstract:in 26 loci coding for the production of protein products is analyzed in three populations of Plethodon welleri and in 26 populations of Plethodon dorsalis. Protein variation patterns are not consistent with the variation of morphological characters upon which the taxonomic status of these populations has been evaluated. The taxonomic division of P. welleri into subspecies is inconsistent with the electrophoretic data. P. dorsalis includes two groups of populations whose electrophoretic divergence is greater than that observed in any species previously studied. They do not correspond with previously recognized subspecies. Measures of genetic identity (Nei's /) and of population subdivision (Wright's FST) indicate that P. dorsalis is divided into a number of genetically isolated units. The FST values reported for this species are greater than any such values reported previously. It is suggested that the taxonomic recognition of species denotes the presence of a highly canalized phenotype which has been maintained over genetically diverse populations, rather than the genetically homogeneous units of other vertebrate species. Morphological divergence appears to be unrelated to the amount of electrophoretically detected genetic differentiation occurring among populations of the P. welleri group. [Electrophoresis; geographic variation; Amphibia; Plethodontidae.
-
testing hypotheses of speciation in the Plethodon jordani species complex with allozymes and mitochondrial dna sequences
Biological Journal of The Linnean Society, 2006Co-Authors: David W Weisrock, Allan LarsonAbstract:Trp , and tRNA Ala from 438 salamanders) from 100 populations representing six species of the P. jordani complex ( Plethodon amplus , Plethodon cheoah , Plethodon jordani , Plethodon meridianus , Plethodon metcalfi , and Plethodon montanus ) with comparative analyses of previously published allozymic data to reconstruct the evolutionary history of this group and to diagnose species lineages. Analyses of mitochondrial haplotypic data include nested-cladistic analysis of phylogeography, analysis of molecular variance, hierarchical analysis of nucleotide-diversity measures, and likelihood-based estimates of recent temporal changes in population size. New analyses of allozymic data include multidimensional scaling and principal component analyses, and both data sets are analysed and compared for congruent genetic structure using Mantel correlation tests. These analyses in combination identify the six named species as distinct evolutionary lineages despite sporadic genetic exchanges among them and some discordance between mitochondrial DNA and allozymic markers. Sexual isolation is not complete for any pair of these six species, but they replace each other geographically and appear to block the geographical spreading of their neighbours. The P. jordani complex is a strong study system for investigating the genetic and ecological processes responsible for vicariant speciation. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 25‐51. ADDITIONAL KEYWORDS: General Lineage Concept ‐ introgression ‐ nested-cladistic analysis ‐ phylogeography ‐ Plethodontidae ‐ salamander ‐ southern Appalachian Mountains.
-
phylogeographic analysis of mitochondrial gene flow and introgression in the salamander Plethodon shermani
Molecular Ecology, 2005Co-Authors: David W Weisrock, Kenneth H Kozak, Allan LarsonAbstract:Plethodon shermani comprises a series of geographically disjunct populations occupying high-elevation mountain isolates. These populations hybridize at their borders with salamanders of the Plethodon glutinosus species complex, and past range expansions inferred from Pleistocene climatic cycles may have increased the possible genetic interactions between P. shermani and species of the P. glutinosus complex. Because mitochondrial DNA haplotypes often show introgression across species borders, we survey mtDNA variation for evidence of past and ongoing genetic interactions between P. shermani, its close relative Plethodon cheoah, and species of the P. glutinosus complex. Ongoing hybridization with the P. glutinosus-complex species Plethodon teyahalee is accompanied by extensive mitochondrial introgression in some Unicoi populations of P. shermani, but it has little genetic impact on P. shermani populations outside hybrid zones at three other isolates (Tusquitee, Wayah Bald, Standing Indian). Some Unicoi populations of P. shermani exhibit mtDNA evidence of past hybridization with diverse lineages from P. aureolus and P. glutinosus. The Tusquitee isolate of P. shermani is also characterized by mtDNA haplotypes most closely related to Plethodon aureolus and P. glutinosus, presumably introduced by past genetic contact with these species or with introgressed populations of Unicoi P. shermani. The mtDNA variation in sampled populations of the Wayah Bald and Standing Indian isolates of P. shermani appears largely unaffected by ongoing hybridization. Principal components analyses of allozymic data indicate that P. shermani isolates collectively form a genetically homogeneous unit clearly demarcated from species with which they have had current or past genetic interactions. Rapid mtDNA introgression associated with transient contacts between P. shermani and other species permits a fine-level resolution of evolutionary lineages not evident from allozymic data.
Dean C. Adams - One of the best experts on this subject based on the ideXlab platform.
-
complex species interactions lead to unpredictable outcomes in Plethodon
Herpetologica, 2013Co-Authors: Jennifer Deitloff, Jessica D Petersen, Dean C. AdamsAbstract:Abstract: Evolutionary and ecological theory generates testable predictions concerning the effects of species interactions on ecological, behavioral, and morphological traits. Throughout Ohio, two closely related and ecologically similar salamander species, Plethodon cinereus and P. electromorphus, occur in similar habitats and in many localities are found in sympatry. Geographic and behavioral patterns previously described between these two species could be the result of interspecific competition, a hypothesis that also predicts distinct patterns of resource use, morphological variation, or both when the two species occur in sympatry. Here we tested these predictions by examining patterns of resource use and morphology in sympatry and compared them to patterns observed in allopatric populations of each species. We found that morphological differences in head shape between species were location-specific, with morphological divergence occurring at some sympatric locations and convergence occurring at other...
-
the evolution of large scale body size clines in Plethodon salamanders evidence of heat balance or species specific artifact
Ecography, 2011Co-Authors: Dean C. Adams, James O ChurchAbstract:A major goal in macroecology is to determine how body size varies geographically, and explain why such patterns exist. Recently, a grid-cell assemblage analysis found significant body size trends with latitude and temperature in Plethodon salamanders, and support for the heat-balance hypothesis as a possible explanation for these trends. Here we demonstrate that the heat-balance hypothesis is unlikely to have generated this pattern, and that there is no overall body size trend with temperature in Plethodon. Using data from 3155 local Plethodon assemblages, we find no support for body size clines with latitude, and no relationship between body size and temperature. We also found that body size did not covary with elevation, in contrast to what was predicted by heat-balance. We then examined the various scenarios under which body size clines across grid-cell assemblages could evolve via heat-balance, and found that none were tenable in light of the existing data. Instead, a single, widely distributed species was responsible for the pattern across grid-cell assemblages. Finally, we examined why phylogenetic eigenvector regression does not account for phylogenetic non-independence among taxa, and should not be used to account for shared evolutionary history in assembly-level analyses. Assemblagelevel patterns are a useful means of assessing biogeographic trends, and are an important complement to within-species and cross-species patterns. However, while the use of grid-cell assemblage approaches from digital databases is expedient, their results must be examined critically, and whenever possible, compared with data obtained from local species assemblages (particularly for ecological mechanisms that operate at the level of individuals). Finally, our results emphasize the importance of using corroborative data to evaluate alternative hypotheses, so that potential mechanisms that explain bioegeographic patterns are properly assigned.
-
Quantitative Genetics and Evolution of Head Shape in Plethodon Salamanders
Evolutionary Biology, 2011Co-Authors: Dean C. AdamsAbstract:The evolution of morphological diversity via selection requires that morphological traits display significant heritable genetic variation. In Plethodon salamanders, considerable evidence suggests that head shape evolves in response to selection from interspecific competition, yet the genetic underpinnings of head shape have not been quantitatively examined. Here I used geometric morphometrics and quantitative genetics to assess heritable patterns of head shape variation from hatchling salamanders in two Plethodon species ( P. cinereus and P. nettingi ). Head shape differed significantly between species and among clutches within species, suggesting that a sizeable proportion of head shape variation was the result of clutch effects. Further, using a full-sib animal model and restricted maximum likelihood (REML), I identified large values of maximal additive heritability for all study localities ( $$ h_{\max }^{2} > 0.65 $$ ), revealing that Plethodon exhibit considerable heritable genetic variation for head shape. Comparisons of the components of heritable shape variation showed that the magnitude of shape heritability ( $$ h_{\max }^{2} $$ ) did not differ among localities or species. Therefore, the potential microevolutionary shape change displayed by the two species would be similar if they were exposed to comparable selective forces. However, the direction of maximal shape heritability in morphospace differed between P. cinereus and P. nettingi, indicating that potential evolutionary shape change along these heritability trajectories would diverge between the two species. This finding implies that distinct head shapes could evolve in the two species, even if subjected to the same selection pressure. When combined with previous knowledge of patterns of head shape variation among species and ecological selection on head shape, these findings suggest that microevolutionary and macroevolutionary trends of morphological diversification in Plethodon may be explained as a result of the interaction between ecological selection and underlying patterns of genetic covariance for this multi-dimensional trait.
-
morphology is decoupled from interspecific competition in Plethodon salamanders in the shenandoah mountains usa
Herpetologica, 2008Co-Authors: Erin M Myers, Dean C. AdamsAbstract:Interspecific competition plays an important role in structuring ecological communities and generating patterns of phenotypic diversification. In the Shenandoah Mountains of Virginia, strong interspecific competition between P. cinereus and P. shenandoah shapes the geographic distributions of these species and relegates P. shenandoah to sub-optimal habitat. However, while many Plethodon salamander communities exhibit phenotypic shifts resulting from interspecific competition, the morphological consequences of competition in this system have not been investigated. We examined head shape variability of Plethodon cinereus and P. shenandoah to determine whether phenotypic patterns of variation were consistent with the hypothesis of interspecific competition. Across all three mountains where P. shenandoah is found, we identified significant species-specific differences in head shape. We also found significant phenotypic shifts between allopatric P. cinereus located at lower elevations and sympatric P. cinereus located at higher elevations. However, there was no evidence of accentuated phenotypic divergence in the sympatric contact zone between the two species. Thus, while there was evidence of a character shift in P. cinereus, patterns of character divergence between species associated with interspecific competition were not found. These observations suggest that morphological variation is decoupled from ecological interactions in this system, and aggressive interactions between the two species do not elicit a phenotypic response as seen in other Plethodon communities.
-
interspecific aggression in ohio Plethodon implications for competition
Herpetologica, 2008Co-Authors: Jennifer Deitloff, Dean C. Adams, Brian F M Olechnowski, Robert G JaegerAbstract:Interspecific competition between closely-related and ecologically similar species may limit geographic ranges and fine-scale sympatry, especially when one species is aggressive toward another species. Throughout Ohio, two closely-related salamander species, Plethodon cinereus and P. electromorphus, can be found in similar habitats. While the distributions of the two species generally overlap through much of this region, a finer-scale examination of their distributions indicates that many areas within the zone of sympatry contain only one or the other species. This geographic pattern suggests that the two species are interacting. In this study, we examined the behavioral responses of individuals from allopatric populations of both species to provide an initial understanding of their interactions. This study represents interactions between ‘novel’ biotic stimuli, as individuals from allopatry have not previously encountered members of the congeneric species. We found that allopatric populations of P. elect...
David W Weisrock - One of the best experts on this subject based on the ideXlab platform.
-
testing hypotheses of speciation in the Plethodon jordani species complex with allozymes and mitochondrial dna sequences
Biological Journal of The Linnean Society, 2006Co-Authors: David W Weisrock, Allan LarsonAbstract:Trp , and tRNA Ala from 438 salamanders) from 100 populations representing six species of the P. jordani complex ( Plethodon amplus , Plethodon cheoah , Plethodon jordani , Plethodon meridianus , Plethodon metcalfi , and Plethodon montanus ) with comparative analyses of previously published allozymic data to reconstruct the evolutionary history of this group and to diagnose species lineages. Analyses of mitochondrial haplotypic data include nested-cladistic analysis of phylogeography, analysis of molecular variance, hierarchical analysis of nucleotide-diversity measures, and likelihood-based estimates of recent temporal changes in population size. New analyses of allozymic data include multidimensional scaling and principal component analyses, and both data sets are analysed and compared for congruent genetic structure using Mantel correlation tests. These analyses in combination identify the six named species as distinct evolutionary lineages despite sporadic genetic exchanges among them and some discordance between mitochondrial DNA and allozymic markers. Sexual isolation is not complete for any pair of these six species, but they replace each other geographically and appear to block the geographical spreading of their neighbours. The P. jordani complex is a strong study system for investigating the genetic and ecological processes responsible for vicariant speciation. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 25‐51. ADDITIONAL KEYWORDS: General Lineage Concept ‐ introgression ‐ nested-cladistic analysis ‐ phylogeography ‐ Plethodontidae ‐ salamander ‐ southern Appalachian Mountains.
-
phylogeographic analysis of mitochondrial gene flow and introgression in the salamander Plethodon shermani
Molecular Ecology, 2005Co-Authors: David W Weisrock, Kenneth H Kozak, Allan LarsonAbstract:Plethodon shermani comprises a series of geographically disjunct populations occupying high-elevation mountain isolates. These populations hybridize at their borders with salamanders of the Plethodon glutinosus species complex, and past range expansions inferred from Pleistocene climatic cycles may have increased the possible genetic interactions between P. shermani and species of the P. glutinosus complex. Because mitochondrial DNA haplotypes often show introgression across species borders, we survey mtDNA variation for evidence of past and ongoing genetic interactions between P. shermani, its close relative Plethodon cheoah, and species of the P. glutinosus complex. Ongoing hybridization with the P. glutinosus-complex species Plethodon teyahalee is accompanied by extensive mitochondrial introgression in some Unicoi populations of P. shermani, but it has little genetic impact on P. shermani populations outside hybrid zones at three other isolates (Tusquitee, Wayah Bald, Standing Indian). Some Unicoi populations of P. shermani exhibit mtDNA evidence of past hybridization with diverse lineages from P. aureolus and P. glutinosus. The Tusquitee isolate of P. shermani is also characterized by mtDNA haplotypes most closely related to Plethodon aureolus and P. glutinosus, presumably introduced by past genetic contact with these species or with introgressed populations of Unicoi P. shermani. The mtDNA variation in sampled populations of the Wayah Bald and Standing Indian isolates of P. shermani appears largely unaffected by ongoing hybridization. Principal components analyses of allozymic data indicate that P. shermani isolates collectively form a genetically homogeneous unit clearly demarcated from species with which they have had current or past genetic interactions. Rapid mtDNA introgression associated with transient contacts between P. shermani and other species permits a fine-level resolution of evolutionary lineages not evident from allozymic data.
Carolyn Martin - One of the best experts on this subject based on the ideXlab platform.
-
salamanders Plethodon cinereus go for more rudiments of number in an amphibian
Animal Cognition, 2003Co-Authors: Claudia Uller, Robert G Jaeger, Gena Guidry, Carolyn MartinAbstract:Techniques traditionally used in developmental research with infants have been widely used with nonhuman primates in the investigation of comparative cognitive abilities. Recently, researchers have shown that human infants and monkeys select the larger of two numerosities in a spontaneous forced-choice discrimination task. Here we adopt the same method to assess in a series of experiments spontaneous choice of the larger of two numerosities in a species of amphibian, red-backed salamanders (Plethodon cinereus). The findings indicate that salamanders "go for more," just like human babies and monkeys. This rudimentary capacity is a type of numerical discrimination that is spontaneously present in this amphibian.