Richard Highton

University of Maryland, College Park | UMD, UMCP, University of Maryland College Park · Department of Biology

Aim: The river drainages of the Appalachian Mountains have experienced a dynamic history as glacial cycles, stream capture and other geological processes have led to the fragmentation and fusion of formerly isolated palaeodrainages. Some ancient rivers have gone extinct, including portions of the great Teays River. Here we investigate the contribut...

Species are a fundamental unit of biodiversity, yet can be challenging to delimit objectively. This is particularly true of species complexes characterized by high levels of population genetic structure, hybridization between genetic groups, isolation by distance, and limited phenotypic variation. Previous work on the Cumberland Plateau Salamander,...

Concatenated analyses using RAxML, including a phylogeny of the nuclear loci, and a phylogeny with both nuclear and mtDNA loci. Figures H-I. (PDF)

Detailed sampling information. Table A. (PDF)

Gene trees for nuclear loci. Figures C-G. (PDF)

Genealogical sorting index results. Table I. (PDF)

Brownie. Results, Tables C-H, Figures J-K. (PDF)

Multidivtime analyses. Methods, Table B, Figures A, B. (PDF)

A study of DNA sequence variation in the plethodontid salamander Batrachoseps attenuatus by Martínez-Solano et al. (2007) revealed more species than acknowledged by the authors. They sequenced 677 base pairs of the cytochrome-b mitochondrial gene in 178 individuals from 123 populations of the currently recognized species B. attenuatus from througho...

Quantitative biochemical comparisons of albumin differences within the snake family Colubridae were performed, using micro-complement fixation analysis. These tests support the recognition of the subfamilies Colubrinae and Natricinae, and corroborate their distinctness from snakes usually placed in the subfamilies Xenodontinae and Lycodontinae. Gen...

Functionally equivalent genes may evolve heterogeneously across closely related taxa as a consequence of lineage-specific selective pressures. Such disparate evolutionary modes are especially prevalent in genes that encode postcopulatory reproductive proteins, presumably as a result of sexual selection. We might therefore expect genes that mediate...

Recent declines and extinctions of amphibian populations have been reported in many areas of the world. A majority of the documented declines are in easily detectable anuran species, including flatwoods salamanders (Ambystoma cingulatum), southern dusky salamanders (Desmognathus auriculatus), and green salamanders (Aneides aeneus. However, other pu...

ABSTRACT.—A new species of Scinax is described from Venezuela. It is the only species known from the Venezuelan Andes, between 600 and 1700 m. It differs from other species in the genus by its yellow coloration in life, two dorsolateral stripes, and unpatterned posterior surfaces of thighs. A description of the call is provided. The new species is...

Studies on allozyme variation in eastern plethodontid salamanders of the woodland genus Plethodon have revealed a large number of cryptic species. Genetic variation within and among species reveals patterns of speciation. In the late Miocene and early Pliocene there appear to have been only five clades of eastern North American Plethodon that still...

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 furthe...

A reanalysis of our allozyme data (Dowling et al., 1996) for four slowly-evolving loci in 215 species of snakes by Buckley et al. (2000) concluded that because of ties in genetic distances our published UPGMA tree had "little resolution, indicating that these data are highly ambiguous regarding higher-level snake phylogeny." They also concluded tha...

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...

One of the important discoveries resulting from the application of molecular methods to systematics is the presence of far more species in many groups of organisms than have been identified by classical morphological studies. This finding has been especially significant in amphibian systematics because speciation in this group often has not been ac...

Allozyme data for 67 samples of Plethodon richmondi and P. electromorphus from the contact zone between the two species in northern Kentucky and surrounding areas indicate that nine populations show evidence of hybridization between the two species. Six of these populations are genetically more similar to P. electromorphus and three are more simila...

I analyzed geographic protein variation in 24 genetic loci of five previously unstudied species of the Plethodon cinereus group (P. hoffmani, P. hubrichti, P. nettingi, P. richmondi, and P. shenandoah) using the technique of electrophoresis, utilizing the same methods as reported previously for P cinereus and P. serratus. Plethodon hoffmani consist...

Reciprocal transplantation of the southern Appalachian salamander Plethodon jordani between the Great Smoky Mountains and the Balsam Mountains, in field competition experiments by Nelson G. Hairston, St. in 1974-1978, provided an opportunity for observing the genetic interactions between the two populations in their first generation of sympatry. Na...

Stebbins (1949) regarded the western North American plethodontid salamander Ensatina eschscholtzii as a polytypic species with seven subspecies distributed in a ring around the Great Valley of California. The terminal subspecies overlap in southern California. This complex has been considered a classical example of a circular overlap or 'ring speci...

We present an initial evaluation of relationships among a diverse sample of 215 species of snakes (8% of the world snake fauna) representing nine of the 16 commonly-recognized families. Allelic variation at four slow-evolving. protein-coding loci, detected by starch-gel electrophoresis, was found to be informative for estimating relationships among...

Geographic protein variation in 26 genetic loci from six samples of Pseudacris brimleyi was analyzed by standard and sequential starch-gel electrophoresis. A single population of P. feriarum was included as an outgroup. In these seven populations, standard methods detected 59 alleles while sequential analysis revealed 31 additional alleles at 14 lo...

An analysis of the relationship between the number of loci utilized in an electrophoretic study of genetic relationships and the statistical support for the topology of UPGMA trees is reported for two published data sets. These are Highton and Larson (Syst. Zool.28:579-599, 1979), an analysis of the relationships of 28 species of plethodonine salam...

Relationships among North American plethodontid salamanders have been the subject of numerous molecular studies. In particular, immunological investigations of albumin evolution using the quantitative technique of micro-complement fixation have provided insights into relationships between the genera Ensatina and Plethodon, as well as within Plethod...

The bootstrapping method of determining confidence in the topology of phylogenetic trees has been applied to electrophoretic protein data for two groups of amphibians: salamanders of two North American genera (Aneides and Plethodon) of the tribe Plethodontini and Holarctic hylid frogs. Some current methods of phylogenetic reconstruction for electro...

The initial essay by the first 2 authors reviews alternative concepts and operational approaches to biological species as they apply to herpetology, and argues for a concept of species that is consistent with recovered phylogenetic history. The authors also believe that an arbitrary level of genetic distance or morphological divergence as a "specie...

Immunological and electrophoretic protein comparisons are analyzed in conjunction with a cladistic analysis of morphological variation to evaluate the rates and modes of morphological evolution in the salamanders of the tribe Plethodontini. Phylogenetic inferences from different data sets are highly congruent. The protein comparisons indicate that...

Twenty-one protein loci of Aneides hardii from three isolated mountain ranges of New Mexico were analyzed electrophoretically. Genetic divergence is very small (D less than .03) and the three populations probably had a common ancestor during the latter portion of the Pleistocene Epoch.

Highton, Richard and Allan Larson (Department of Zoology, University of Maryland, College Park, Maryland, 20742) 1979. The genetic relationships of the salamanders of the genus Plethodon. Syst. Zool. 28:579–599 .—An electrophoretic comparison of proteins is used to evaluate the genetic relationships of the salamanders of the genus Plethodon . The g...

Comparative studies were made of albumin evolution in all species of the salamander genera Plethodon and Ensatina. The albumins of all species were compared by the quantitative micro-complement fixation technique. Ensatina was seen to be phyletically remote from all species of Plethodon. The eastern large and eastern small Plethodon were shown to b...

An electrophoretic study of 23 genetic loci in 20 samples of Plethodon ouachitae and P. caddoensis, species endemic to the Ouachita Mountains of Arkansas and Oklahoma, indicates that there is a third member of the group, as genetically different from the two named species as they are from each other. It is described as a new species, Plethodon four...

Variation 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 divi...

Genetic variation at 12 loci was investigated electrophoretically in southern Appalachian populations of salamanders of the Desmognathus ochrophaeus species complex. Levels of heterozygosity and allele frequencies varied markedly among the 31 populations sampled. The electrophoretic results indicate that two reproductively isolated forms are broadl...

Geographic variation at 24 polypeptide loci was studied in 24 populations of the red-backed salamander, Plethodon cinereus. At 6 loci, differentiation of the continuously distributed northern populations from the five southern isolates is complete or almost complete. The latter are recognized as a separate species, P. serratus. Differentiation with...

Female parent-offspring phenotypic data on color morph frequencies in the red-backed salamander, Plethodon cinereus, were obtained from two Virginia localities (164 broods from Greene County and 97 broods from Giles County). The color morph data indicate that the striped morph is genetically dominant in Giles County and recessive in Greene County....

Cover title. "31 December 1962." Includes bibliographical references (p. 359-367). Methods -- Pigmentation in the genus Plethodon -- Variation in the number of vomerine teeth -- Treatment of infraspecific variation -- Systematics: Plethodon -- Key to salamanders of the genus Plethodon -- The western Plethodons -- The eastern Plethodons -- The easte...

Cover title. "March, 1956." Includes bibliographical references (p. 95-96). Sexual dimorphism -- Geographic variation -- Taxonomy and nomenclature -- Key to the subspecies of "Stilosoma extenuatum" -- Origin of subspecific differentiation -- Ecological notes. A study of variation of the short-tailed snake has indicated that there are three well-def...

Geographic variation of color phase frequency and number of trunk vertebrae in the terrestrial salamander Plethodon cinereus on Long Island, New York is described and compared with that in adjacent mainland areas. The concordance in the geographic variation of the two characters is much higher on Long Island than is known anywhere else in the range...

Plethodon richmondi shenandoah, n. ssp., occurs with P. cinereus in the Blue Ridge physiographic province of Virginia. It has a modal number of 19 trunk vertebrae, color phase dimorphism, a narrow dorsal stripe in the striped phase, reduced brassy iridophore pigmentation in the unstriped phase, and a dark belly. It is apparently separated into thre...

The male and female reproductive cycles, growth and maturity of Plethodon glutinosus in western Maryland and southwestern Pennsylvania are compared with the life history in Florida. Data from Illinois, Louisiana, and Virginia provide additional information on geographic variation. In Maryland and Pennsylvania only about half of the mature females o...

Geographic and individual variation in the number of body vertebrae in the salamander Plethodon cinereus has been described. The number of trunk vertebrae in 488 offspring in 78 broods collected in the vicinity of Mountain Lake, Giles County, Virginia, was shown to be correlated with the number of body vertebrae in their female parents, showing tha...