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Climate change is expected to systematically alter the distribution and population dynamics of species around the world. The effects are expected to be particularly strong at high latitudes and elevations, and for ectothermic species with small ranges and limited movement potential, such as salamanders in the southern Appalachian Mountains. In this study, we sought to establish baseline abundance estimates for plethodontid salamanders (family: Plethodontidae) over an elevational gradient in Great Smoky Mountains National Park. In addition to generating these baseline data for multiple species, we describe methods for surveying salamanders that allow for meaningful comparisons over time by separating observation and ecological processes generating the data. We found that Plethodon jordani had a mid‐elevation peak (1,500 m) in abundance and Desmognathus wrighti increased in abundance with elevation up to the highest areas of the park (2025 m), whereas Eurycea wilderae increased in abundance up to 1,600 m and then plateaued with increasing uncertainty. Litter depth, herbaceous ground cover, and proximity to stream were also important predictors of abundance (dependent upon species), whereas daily temperature, precipitation, ground cover, and humidity influenced detection rates. Our data provide some of the first minimally biased information for future studies to assess changes in the abundance and distribution of salamanders in this region. Understanding abundance patterns along with detailed baseline distributions will be critical for comparisons with future surveys to understand the population and community‐level effects of climate change on montane salamanders., Map of elevation and site locations for study.

Wildlife are faced with numerous threats to survival, none more pressing than that of climate change. Understanding how species will respond behaviorally, physiologically, and demographically to a changing climate is a cornerstone of many contemporary ecological studies, especially for organisms, such as amphibians, whose persistence is closely tied to abiotic conditions. Activity is a useful parameter for understanding the effects of climate change because activity is directly linked to fitness as it dictates foraging times, energy budgets, and mating opportunities. However, activity can be challenging to measure directly, especially for secretive organisms like plethodontid salamanders, which only become surface active when conditions are cool and moist because of their anatomical and physiological restrictions. We estimated abiotic predictors of surface activity for the seven species of the Plethodon jordani complex. Five independent data sets collected from 2004 to 2017 were used to determine the parameters driving salamander surface activity in the present day, which were then used to predict potential activity changes over the next 80 yrs. Average active seasonal temperature and vapor pressure deficit were the strongest predictors of salamander surface activity and, without physiological or behavioral modifications, salamanders were predicted to exhibit a higher probability of surface activity during peak active season under future climate conditions. Temperatures during the active season likely do not exceed salamander thermal maxima to cause activity suppression and, until physiological limits are reached, future conditions may continue to increase activity. Our model is the first comprehensive field-based study to assess current and future surface activity probability. Our study provides insights into how a key behavior driving fitness may be affected by climate change.

The size of an organism is perhaps its most overt physical characteristic, and variation in body size has long been of interest to biologists. Bergmann's rule has been actively studied and debated for more than 150 years. Despite this long history, the generality and applicability of Bergmann's rule to ectothermic organisms generally, and to plethodontid salamanders specifically, has resulted in an extensive and conflicting literature. Regardless of mechanism, clinal variation in body size has been widely observed in plethodontid salamanders and other ectothermic vertebrates. In this study, we assessed the change in adult body size of four plethodontid salamanders (Desmognathus imitator, D. ocoee, D. wrighti, and Plethodon jordani) across a 1,350 m elevational gradient in Great Smoky Mountains National Park. Using 1,293 observations of salamanders at 25 sites, we found clear and significant patterns of increasing adult body size with elevation in all four species. Average rates of increase ranged from 1.0...

Aim Approximately 32.5% of all amphibian species are globally threatened, and amphibian extinctions have been recorded worldwide. Individual studies rarely give full consideration to multiple potential drivers of observed biological change, instead tending to attribute changes to a single driver. Here, I tested for impacts of land use and climate change on range changes in a community of plethodontid salamanders living from 518 to 2036 m elevation in a global hotspot for amphibian diversity. Location The southern Appalachian Mountains. Methods I resurveyed 18 elevational transects that had originally been surveyed by Nelson Hairston in 1940, 1947 and 1949. I recorded range changes for nine species that Hairston studied and determined the extent to which the recorded expansions or contractions could be attributed to changes in forest stand, climate and competition, singly or in combination. Results ‘Montane’ species, which occur only on mountaintops, had expanded their lower elevational limits downwards. ‘Foothill’ species, which occur at lower elevations than montane species, had expanded their upper elevational limits upwards. Main conclusions For montane species these downward expansions appear to be the result of two processes: local cooling of the climate and maturation of forests after the cessation of large-scale logging operations c. 80 years ago. In contrast, changes in upper elevational range limits of foothill species are probably the result of a suite of complex and interacting drivers, including, but not limited to, maturation of forests, changes in climate, and interactions with other species.

Many animal and plant taxa reach their highest endemism and species richness in montane regions. The study of elevational range limits is central to understanding this widespread pattern and to predicting the responses of montane species to climate change. Yet, because large-scale manipulations of the distributions of most species are difficult, the causes of species’ elevational range limits (e.g. competitive interactions, physiological specialization) are poorly understood. Here, we harness the power of new mechanistic approaches to dissect the factors that underlie the elevational replacement of two salamander species in the Appalachian Highlands. Our results challenge the long-held idea that competitive interactions drive the lower elevational range limits of montane species and that physiological stress prevents low-elevation species from expanding to high elevations. We show that physiological constraints drive the lower elevational range limit of the montane-endemic species, Plethodon jordani. Conversely, we find that competition with P. jordani prevents the low-elevation species, P. teyahalee, from expanding its range to include higher-elevation habitats. These results are broadly consistent with the biogeography and behavior of other montane species, suggesting that similar mechanisms underlie patterns of elevational zonation across a variety of taxa and montane regions. To the extent that our findings are taxonomically and geographically widespread, these results challenge the idea that competitive release at species’ lower elevational range limits is driving the downslope range shifts exhibit by some montane taxa. Instead, our results raise the sobering possibility that even small changes in climate might cause erosion of the ranges of many high-elevation species.

Hybrid zones have yielded considerable insight into many evolutionary processes, including speciation and the maintenance of species boundaries. Presented here are analyses from a hybrid zone that occurs among three salamanders -Plethodon jordani, Plethodon metcalfi and Plethodon teyahalee- from the southern Appalachian Mountains. Using a novel statistical approach for analysis of non-clinal, multispecies hybrid zones, we examined spatial patterns of variation at four markers: single-nucleotide polymorphisms (SNPs) located in the mtDNA ND2 gene and the nuclear DNA ILF3 gene, and the morphological markers of red cheek pigmentation and white flecks. Concordance of the ILF3 marker and both morphological markers across four transects is observed. In three of the four transects, however, the pattern of mtDNA is discordant from all other markers, with a higher representation of P. metcalfi mtDNA in the northern and lower elevation localities than is expected given the ILF3 marker and morphology. To explore whether climate plays a role in the position of the hybrid zone, we created ecological niche models for P. jordani and P. metcalfi. Modelling results suggest that hybrid zone position is not determined by steep gradients in climatic suitability for either species. Instead, the hybrid zone lies in a climatically homogenous region that is broadly suitable for both P. jordani and P. metcalfi. We discuss various selective (natural selection associated with climate) and behavioural processes (sex-biased dispersal, asymmetric reproductive isolation) that might explain the discordance in the extent to which mtDNA and nuclear DNA and colour-pattern traits have moved across this hybrid zone.

Courtship behavior and ♂ - ♂ interactions in the salamanders Ambystoma maculatum, Ambystoma tigrinum and Plethodon jordani were investigated with the aim of determining their adaptive significance. The courtship behavior of approximately 30 pairs of A. maculatum, 10 pairs of A. tigrinum and 50 pairs of P. jordani was observed. Behaviors were recorded by verbal transcription, motion picture and still photography. A. maculatum ♂ ♂ court rapidly, deposit many spermatophores, have simple behavior and low success with each spermatophore. P. jordani ♂ ♂ court slowly, usually deposit a single spermatophore, have complex behavior and high success with each spermatophore. A. tigrinum is intermediate in these respects. ♂ ♂ of the two Ambystoma species actively cover the spermatophores of rival ♂ ♂. Male A. tigrinum and P. jordani dupe rival ♂ ♂ into unprofitable spermatophore depositions by mimicking female behavior. Male A. tigrinum actively transport the ♀ away from rivals. Male P. jordani chase rivals away from the ♀. A hypothesis is proposed which relates the evolution of courtship speed, spermatophore number and sexual defenses to the length of the courtship season, the probability of intrusion by rival ♂ ♂ and the sexual receptivity of the ♀. Zusammenfassung Drei Arten von Salamandern unterscheiden sich deutlich in der Lange der Zeit, die das ♂ vor einem ♀ balzt, ehe es die Spermatophore absetzt, und in der Zahl der Spermatophoren, die es pro Balz absetzt. Daraus lassen sich die folgenden Hypothesen zur Evolution der Salamanderbalz ableiten. Die Balzdauer pro Spermatophore scheint ein Kompromis zwischen dem Erfolg bei einem bestimmten ♀ und der Ausschaltung von Rivalen zu sein. Je langer die Balz ist, desto wahrscheinlicher findet das ♀ die Spermatophore. Also sollte das ♂ viel Zeit in jede Spermatophore investieren (z. B. Plethodon). Wenn aber Rivalen hinzukommen, konnten sie in dieser Zeit die Besamung stehlen. Deshalb balzen die polyandrische Ansammlungen bildenden Arten (z. B. Ambystoma maculatum) schnell und investieren wenig Zeit in jede Spermatophore. Die Zahl von Spermatophoren pro Balz scheint ein Kompromis zwischen dem Erfolg bei einem bestimmten ♀ und der Dauer der Balzzeit. Die ♂ ♂ haben nur einen beschrankten Vorrat von Spermatophoren. ♂ ♂, die in der Balz Spermatophoren sparen, konnten mehr ♀♀ begatten als ♂ ♂, die nicht sparsam sind. Das kann sogar den Nachteil eines geringeren Erfolgs pro ♀ wettmachen, wenn die Fortpflanzungszeit lang ist (z. B. Plethodon). Mannliche Salamander drangen sich in die Balz anderer ♂ ♂ hinein. Solche Storungen konnen einen Selektionsdruck auf Verteidigung des ♀, schnelle Balz, und auf Vergroserung der Zahl von Spermatophoren je Balz ausuben.

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.

Summary 1. Over the last 30 years there has been a great deal of interest in investigating patterns of species co-occurrence across a number of locations, which has led to the development of numerous methods to determine whether there is evidence that a particular pattern may not have occurred by random chance. 2. A key aspect that seems to have been largely overlooked is the possibility that species may not always be detected at a location when present, which leads to ‘false absences’ in a species presence/absence matrix that may cause incorrect inferences to be made about co-occurrence patterns. Furthermore, many of the published methods for investigating patterns of species co-occurrence do not account for potential differences in the site characteristics that may partially (at least) explain non-random patterns (e.g. due to species having similar/different habitat preferences). 3. Here we present a statistical method for modelling co-occurrence patterns between species while accounting for imperfect detection and site characteristics. This method requires that multiple presence/absence surveys for the species be conducted over a reasonably short period of time at most sites. The method yields unbiased estimates of probabilities of occurrence, and is practical when the number of species is small ( < 4). 4. To illustrate the method we consider data collected on two terrestrial salamander species, Plethodon jordani and members of the Plethodon glutinosus complex, collected in the Great Smoky Mountains National Park, USA. We find no evidence that the species do not occur independently at sites once site elevation has been allowed for, although we find some evidence of a statistical interaction between species in terms of detectability that we suggest may be due to changes in relative abundances.

All animals and plants have intimate associations with microbes. Opinion has shifted from viewing microbes primarily as pathogens to the idea that healthy animals and plants carry specialized communities of coevolving microorganisms. However, the generality of this proposition is unknown because surveys rarely compare host-associated microbes with samples from relevant microhabitats. Symbiotic communities might be assembled from local environments with little evolutionary specialization. We evaluated the specificity of bacteria associated with salamander skin in comparison with surfaces in their immediate environments using 16S rRNA sequences. Host-associated and free-living samples were significantly different. However, relative abundances were strongly correlated; the most abundant taxa on salamander skin were also most abundant on moist debris on the forest floor. Thus, although bacterial assemblages on salamander skin are statistically differentiated from those on inanimate surfaces, they are not entirely ‘distinct’. Candidate salamander specialists were few in number and occurred at low relative abundances. Within some OTUs, differences in allele frequency suggested genetic specialization at finer levels. Although host-associated and free-living assemblages were similar, a range of more or less specialized symbiotes was evident and bacteria on salamander skin were often specific genotypes of OTUs commonly found on other moist surfaces in the environment.

Behavioral interactions with native species may influence the invasiveness of introduced species. The salamanders Plethodon glutinosus and P. jordani in the eastern United States share many life history traits and demonstrate complex interspecific interactions that range geographically from competitive exclusion to sympatry. P. jordani was introduced to Mountain Lake Biological Station, Virginia, USA, between the years 1935 and 1945. We tested whether competition for space may influence the invasion of P. jordani into native P. glutinosus habitat by utilizing data from natural distributions, a field experiment, and controlled laboratory experiments. No environmental variables differed where P. glutinosus and P. jordani were collected in the field at the site of P. jordani introduction. In the field experiment, P. glutinosus was more fully exposed during foraging bouts in cages shared with heterospecifics as opposed to ones shared with conspecific salamanders. Condition (mass relative to body length) of salamanders at the end of the 3 months did not differ between conspecific and heterospecific treatments. In the laboratory, P. glutinosus most often attained the single burrow in the arena, but residency status had no effect. Species cohabited the burrow 50% of the time. Pair-wise encounters in the laboratory indicated that both species spend less than 20% of the time in aggressive behaviors as juveniles. Adults showed no behavior interpreted by us as aggression during pair-wise encounters.

We examined intraand interspecific chemical variation in salamander courtship pheromones. The extent to which plethodontid receptivity factor (PRF) and other glandular components vary among populations of Plethodon jordani was analyzed by reverse-phase HPLC. Gland extracts from individuals revealed that males within a population differ in the relative amounts of the glandular components as well as in the presence and absence of components, including PRF. Comparisons between populations showed that each population had a unique elution profile and differed significantly in the relative amounts of PRF and the other extract components. Knowledge about the nature of geographic variation in the courtship pheromone, combined with behavioral tests of female response, will contribute towards understanding how the pheromone evolved.

As part of the Wine Spring Creek ecosystem management project on the Nantahala National forest, North Carolina, we assessed effects of a community restoration fire on small mammals and herpetofauna in the upper slope pitch pine (Pinus rigida) stands, neighboring midslope oak (Quercus spp.) stands and rhododendron (Rhododendron maximum) dominated riparian areas during 1995 and 1996. Using drift-fence arrays with pitfalls and snap-trapping, we collected these small mammals: masked shrew (Sorex cinereus), smoky shrew (S. fumeus), water shrew (S. palustris), pygmy shrew (S. hoyi), northern short-tailed shrew (Blarina brevicauda), deer mouse (Peromyscus maniculatus), white-footed mouse (P. leucopus), golden mouse (Ochrotomys nuttalli), southern red-backed vole (Clethrionomys gapperi), pine vole (Microtus pinetorum) and woodland jumping mouse (Napaeozapus insignis). Herpetofauna collected from drift-fence arrays and time-constrained searches included: eastern newt (Notophtalmus viridescens), seepage salamander (Desmognathus aeneus), mountain dusky salamander (D. ochrophaeus), Blue Ridge two-lined salamander (Eurycea wilderae), spring salamander (Gyrinophilus porphyriticus), Jordan’s salamander (Plethodon jordani), wood frog (Rana sylvatica), five-lined skink (Eumeces fasciatus), eastern garter snake (Thamnophis sirtalis), and northern ringneck snake (Diadophis punctatus). Prior to the prescribed community restoration fire in the spring of 1995, there were no significant differences in small mammal or herpetofauna collections between burned and control areas. Post-treatment in 1995 and 1996, showed no significant differences among collections of most species between burned and control areas. Slope position accounted for more variation among the species of greatest abundance than did burning. Concern for the effects of prescribed fire as a management tool on small mammals and herpetofauna in the southern Appalachians seems unwarranted. # 1999 Elsevier Science B.V. All rights reserved.

1. Neither cold acclimation (2–3°C) nor laboratory captivity affected the amount of hsp 70 in the lungless salamander Plethodon cinereus. 2. Plethodon jordani had substantial amounts of heat shock protein (hsp) 70 present in its tissues when acclimated to 15°C (LD 12:12). 3. The increase in hsp 70 in P. jordani (13.2%) after heat shock at 2°C below its critical thermal maximum (CTMax) (34.1°C) was not statistically significantly higher than the control value. 4. An immunoblot with monoclonal antibody after 2-D SDS PAGE gel indicated that constitutive hsp 70 was the major form of hsp 70 in P. jordani.

The disappearance and return of plethodontid salamanders on clearcuts has been monitored since 1979 in the southern Blue Ridge Mountains at three sites near Highlands, North Carolina. Salamander abundance on 225 m2 plots located on clearcuts and in nearby forest was determined by nightly non-destructive searches. Abundances on clearcut and forest plots at a given site were compared for each year in which sampling occurred. Numbers of salamanders on clearcut plots decreased to 30–50% of forested plots in the first year after logging and were almost zero by the second year. Decreases in standing crop and moisture content of leaf litter seem responsible for salamander disappearance. Salamanders returned to clearcuts 4–6 years after cutting, and their numbers increased rapidly. Linear regressions estimate that salamander numbers on clearcut plots will equal or exceed numbers on forested plots by 20–24 years after cutting. The pattern of salamander return to clearcuts appears closely correlated with the timing of litter layer reformation. All sex and age classes of the most common species, Plethodon jordani, disappear from clearcuts at equal rates, whereas the earliest colonizers are predominantly large adults. Plethodon oconaluftee, a desiccation-resistant species, exists on regenerating clearcuts in disproportionately large numbers. Large adults of all species, including Plethodon oconaluftee, may be better able to withstand the drier, sparse litter cover of young, regenerating stands. Adults might move to clearcuts to avoid competition from smaller and immature salamanders restricted to mature forests with abundant, moist litter. La desaparicion y retorno de salamandras pletodontidas en areas de tala extrema han sido monitoreadas desde 1979 en las montanas Blue Ridge del Sur, en tres sitios de los alrededores de Highlands, Carolina del Norte. La abundancia de las salamandras en areas de 225 m2 localizados en zonas taladas y en bosques cercanos se determino mediante busquedas nocturnas no destructivas. La abundancia en las areas de zonas taladas y bosques en un sitio determinado fueron comparadas para cada ano muestreado. El numero de salamandras en areas taladas disminuyo en un 30–50% con respecto a las areas boscosas en el primer ano posterior a la tala y fue de casi cero el segundo ano. Disminuciones en la cosecha sostenida y contenido de humedad en detritus de hojas parecen ser los responsables de la desaparicion. Las salamandras retornaron a las areas taladas 4–5 anos despues de la tala y sus numeros incrementaron rapidamente. Regresiones lineales estiman que el numero de salamandras en areas taladas igualara o excedera el numero en las areas boscosas en 20–24 anos despues de la tala. El patron de retorno parece estar fuertemente correlacionado con el tiempo de reconstruccion de la capa de detritus. Todas las clases de edades y sexos de la especie mas comun, Plethodon jordani, desaparecieron de las areas taladas a tasas iguales, mientras que los primeros colonizadores son predominantemente adultos. Plethodon oconaluftee una especie resistente a la desecacion, existe en areas de regeneracion en numeros desproporcionadamente grandes. Adultos grandes de todas las especies, incluyendo Plethodon oconaluftee, pueden ser mas aptos para soportar la cobertura de detritus seco y disperso de zonas en regeneracion. Los adultos podrian haberse movido para evitar la competencia con salamandras mas pequenas e inmaduras restringidas a bosques maduros con abundante detritus humedo.

The distribution of 5-HT-like-immunoreactive cell bodies and fibres was studied in the brains of the salamanders Hydromantes italicus, H. genei, Plethodon jordani, Desmognathus ochrophaeus (family Plethodontidae), and Pleurodeles waltl (family Salamandridae). In addition, double-labelling experiments with biocytin were carried out to identify the relationship between serotonergic fibres and neurons involved in the processing of sensory and sensorimotor information. In all species, 5-HT-immunopositive somata are found in the ventral thalamus close to the ventricle forming the paraventricular organ. In the hypothalamus, cells are labelled in the ependymal layer around the infundibular recess and at the lateral edge of the periventricular grey. In the pretectum, a few immunoreactive cells are situated dorsolaterally in the grey matter. In the tegmentum and medulla oblongata, cells of the raphe nuclei are regularly distributed along the midline; labelled perikarya are occasionally found in the cervical spinal cord. 5-HT-like-immunoreactive fibres are widely distributed throughout the nervous system. Densely arborizing fibres are found in the olfactory bulb, striatum and amygdala. Distinct fibre projections extend in the ventral thalamus and tectum. Biocytin tracing of striatal and tectal projection neurons and ascending reticular neurons combined with the demonstration of 5-HT suggest that the striatum, the tectum and the ascending activating system are strongly influenced by 5-HT.

In the summer of 1991 (late May to early September), I measured seasonal levels of plasma androgens in two species of plethodontid salamanders to assess the temporal relationship of elevated plasma androgen levels with spermatogenic events and with sexual behavior. In both species, spermatogenesis occurs in the spring and summer. In one species, Plethodon jordani , mating occurs in the fall. In the other species, Desmognathus ochrophaeus , the mating season is prolonged, occurring both in the fall and in the spring. In P. jordani , plasma testosterone (T) levels were lowest in June and highest in late August, such that elevated plasma T levels coincided with the development of secondary sexual characteristics and the time when mating behavior occurs. Plasma dihydrotestosterone (DHT) levels for P. jordani were lowest in June and rose significantly in mid July when spermiation began. In D. ochrophaeus , plasma T and DHT levels were lowest during June and July and highest in late August. Elevated T and DHT levels coincided with spermiation and with the period when mating behavior occurs. Data for these two salamander species indicate that maximally elevated plasma androgens were temporally dissociated from the peak of spermatogenesis; maximal and androgen levels were more closely associated with spermiation and the development of secondary sexual characteristics.

A 22-kilodalton protein was isolated from the submandibular (mental) gland of the male terrestrial salamander, Plethodon jordani (family: Plethodontidae). This proteinaceous pheromone, termed plethodontid receptivity factor (PRF), was experimentally delivered to the female during courtship and shown to increase female receptivity. In most plethodontid salamanders, ovulation occurs weeks or months after insemination, so the pheromone-induced change in receptivity is the only known function of PRF. The messenger RNAs corresponding to isoforms of PRF were transcribed into complementary DNA, cloned, sequenced, and shown to have homology with cytokines of the interleukin-6 family. Pheromone activity would represent a previously unrecognized function for cytokines.

In salamanders of the species Salamandra salamandra, Pleurodeles waltl , and Plethodon jordani , tectal efferent neurons projecting to the bulbar reticular formation show a stereotyped distribution as revealed by the horseradish peroxidase (HRP) method. The density of these cells increases toward caudal tectal levels reaching its maximum at the isthmic region. Neurons with ipsilaterally descending axons constitute 60–87% and are concentrated in the dorsomedial and ventrolateral sector of the tectal hemisphere, with only few neurons in the intermediate part. The contralaterally descending neurons are concentrated in the lateral sector. This pattern is assumed to reflect a motor map in the coordinates of the salamander neck muscle system.

In the frog Discoglossus pictus and the salamander Plethodon jordani, the morphology and axonal projection pattern of neurons in the medial and dorsal pallium were determined by intracellular biocytin labeling. A total of 77 pallial neurons were labeled in the frog and 58 pallial neurons in the salamander. Within the medial pallium (MP) of the frog, four types of neurons were identified on the basis of differences in their axonal projection pattern. Type I neurons have bilateral projections into telencephalic and diencephalic areas; type II neurons have bilateral projections to telencephalic areas and ipsilaterally descending projections to diencephalic regions; type III neurons have only intratelencephalic connections, and a single type IV neuron has ipsilaterally descending projections. The somata of the four types occupy four nonoverlapping zones. Neurons of the dorsal pallium (DP) project exclusively to the ipsilateral MP and to the dorsal edge of the lateral pallium. In the ventral MP of the salamander, neurons have mostly intratelencephalic projections. Neurons in the dorsal MP project bilaterally to diencephalic and telencephalic regions. Neurons in the medial DP project ipsilaterally to the MP, lateral septum, nucleus accumbens, medial amygdala, and the internal granule layer of the olfactory bulb. In five cases, fibers were found in the commissura hippocampi, but in only two cases could these fibers be followed toward the contralateral MP and septum. Neurons in the lateral DP had no contralateral projections; they projected to the ipsilateral MP and in eight cases to the ipsilateral septum as well. Based on similarities of cytoarchitecture and projection pattern in neurons of the MP and DP, it is proposed that both frogs and salamanders have an MP subdivided into a ventral and dorsal portion, and a DP subdivided into a medial and a lateral portion.

SUMMARY The effects of the visual features of prey-like objects on the orienting behaviour of the salamander Plethodon jordani were studied. Two stimuli (cricket dummies, rectangles), moving in opposite directions, were presented simultaneously on a computer screen. They differed in size, contrast, velocity and movement pattern of the entire body or the body appendages. Size and velocity appeared to be the dominant features; shape was of lesser importance. Contrast and movement pattern were of intermediate importance and local motion of little importance. This rank order was the same when the probability of a response to the different stimuli was estimated by means of the maximum-likelihood method. Cluster analysis revealed that in all animals stimuli could be grouped into five clusters. Among individuals, the rank order of stimuli was similar for high- and low-ranking stimuli and varied for those of intermediate rank; stimuli could be grouped into 3–5 clusters. Our findings favour the view that, in amphibians, prey recognition is guided by a number of visual features acting either alone or in combination and depending on internal motivational or attentional states and individual experience. Movie available on-line: http://www.biologists.com/JEB/movies/jeb3864.html.

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.

Four species of salamander of the family Plethodontidae were examined using electromyographic (EMG) recording during prey-capture behavior to test the hypotheses that the tongue retractor, tongue protractor and jaw depressor muscles are activated simultaneously and in a stereotyped pattern, as was found in other salamanders, and to determine whether species with different tongue morphologies and tongue protraction abilities exhibit different motor control strategies. The results show that sequential activation was observed far more frequently than simultaneous activation; the jaw depressor muscle was activated first, followed by the tongue protractor and then the tongue retractor. Species with short, attached tongues (Desmognathus quadramaculatus and Plethodon jordani) showed simultaneous activation more often than species with long, free tongues (Pseudotriton ruber and Hydromantes supramontis), which showed strongly non-simultaneous activation. Most EMG variables showed no effect of prey-capture success, suggesting that sensory feedback is not involved in modulating the motor pattern during the prey-capture strike. Hydromantes supramontis was examined for modulation of its motor pattern in response to prey distance, and several EMG variables were found to be positively correlated with tongue protraction distance. The motor pattern of strongly non-simultaneous activation of antagonistic tongue muscles has evolved along with the evolution of long, free tongues in plethodontids. The variable motor patterns observed provide further evidence that amphibian feeding in general is not as highly stereotyped as has been previously thought.

We analyzed extracts from specialized male glands that are hypertrophied only during the courtship season in the terrestrial salamander Plethodon jordani (Plethodontidae). Protein analysis and gel electrophoresis revealed approximately 20 bands of protein components (as separated by molecular weight), many of which were glycoproteins. Analyses by high performance liquid chromatography and amino acid sequencing reveal that approximately 85% of the pheromone protein extract was accounted for by two components (and their isoforms). These components were termed Pj-22 and Pj-10 to reflect their respective molecular weights of approximately 22 kDa and 10 kDa. The chemical nature of Pj-22 fits the profile for odorants (known from other vertebrates) that stimulate the vomeronasal organ and can ultimately affect reproductive behavior. Our data are considered in the context of separate behavioral experiments with P. jordani that indicated: (a) delivery of pooled gland extracts resulted in increased female receptivity, and (b) an enriched solution of Pj-22 also was effective at increasing female receptivity.

Two zones of intergradation between populations of Plethodon have been studied for 18 and 20 years, respectively. The data consist of systematic scores of colors, made at least twice annually. Near Heintooga Overlook in the Balsam Mountains (Great Smoky Mountains National Park), the salamanders' cheeks are gray. Proceeding north toward the Smokies, there is increasing frequency and intensity of red color at two, four, and six miles. There has been no change in the scores at any location. The width of the zone and our failure to detect any change can be explained by assuming neutrality of the character and random diffusion during the probable time since contact between the two intergrading forms, which most likely took place after the Hypsithermal Interval, 8,000-5,000 BP. At Coweeta Hydrologic Laboratory in the Nantahala Mountains, Plethodon jordani and P. glutinosus hybridize at intermediate elevations. The lateral white spots of glutinosus decrease and the red on the legs of jordani increases with elevation from 685 m to 1,052 m. At the higher elevation, the proportion of animals scored as "pure" jordani declined significantly from 1974 to 1990, an indication that the hybrid zone is spreading upward. The rate of spread is too great to be explained by random diffusion, so selection for glutinosus characters is the best explanation. The rate of spread of the hybrid zone indicates that hybridization began 60-65 years ago, at the end of the time of intense timbering. Such human disturbances have caused hybridization in other organisms.

Intraspecific spatial relationships of two species of terrestrial salamanders, Plethodon teyahalee and P. jordani were studied in the southern Appalachian Mountains. The movements of 24 P. teyahalee and 40 P. jordani individuals, uniquely marked with fluorescent dust, were monitored from May-Sept. 1983. Distances moved between recaptures were recorded, and the minimum convex polygon method was used to estimate home range areas. Both species occupied fixed home ranges, and all age classes of both species shared on average less than 10% of home range area with a conspecific of the same age or sex. Home ranges of P. teyahalee, the larger species, were smaller, more exclusive, and more likely to contain a retreat hole than home ranges of P. jordani. All 3 yr old or older P. teyahalee had at least one retreat hole in their home range, which they used nearly every night. It appears that retreat holes may be defended by P. teyahalee, but there was no evidence that retreat holes were in limited supply. Home ranges of P. jordani were not associated with cover objects or with retreat holes, which suggests that neither of these resources are defended. The only resource that appears to be used by both species is space (i.e., the forest floor itself, which contains the multi-purpose home range area that both species use for foraging and courtship). This study supports two predictions of the hypothesis that these salamanders are intraspecifically territorial: 1) individuals occupy fixed home ranges; and 2) these areas are exclusive with respect to rivals.

In an attempt to determine whether salamanders (Plethodon jordani) can discriminate between the odors of conspecifics based on proximity of residence, a two-choice system was used to measure the preference of salamanders for the odors of conspecifics of the same sex that occupied adjacent or more distant home ranges. Before the breeding season, the odors of the neighboring conspecifics were preferred to those of non-neighbors. During the breeding season, neither sex showed a significant odor preference, although the females showed a significant change in preference toward the odor of the non-neighboring conspecific. These results indicate the ability of salamanders to discriminate between the odors of conspecifics of the same sex, and suggest the discrimination of odors based on kinship relationships.

Experimental removal of the terrestrial salamander Plethodon jordani from marked plots in the Great Smoky Mountains and the Balsam Mountains of North Carolina, USA resulted in statistically significant increases in the abundance of P. glutinosus in both areas. The increase ap- peared earlier in the Smokies, where the two species overlap by only 70-120 m. Removal of P. glutinosus, the less abundant species, did not result in a statistically significant increase in P. jordani, but did increase the proportion of young in that species. Again, the effect was more pronounced in the Smokies than in the Balsams, where the altitudinal overlap is 1220 m (4000 ft). Stronger compe- tition in the narrow zone of overlap had been predicted on the basis of field distributions, but a measurable level of competition in the wide zone of overlap was surprising. The experiments permitted the direct calculation of coefficients of competition and carrying capacities for both species in both areas. Competition coefficients were higher in the Smokies, but carrying capacities were very similar in the two areas. The experimental approach eliminated the assumptions required for calculating competition coefficients by resource partitioning, and since the experimental design was published before the experiments were begun, the circularity implicit in retrospective analyses was avoided.

Salamanders of the Plethodon glutinosus-P. jordani complex were tested for the ability to distinguish conspecific, sex-specific, and heterospecific chemical cues. Male and female P. glutinosus preferred substrates previously occupied by conspecifics over their own, but randomly chose between substrates marked by male or female conspecifics. This suggests that while these salamanders are able to distinguish between their own and conspecific substrate odours, they are unable to identify sex by means of substrate odours. Experiments using an olfactometer showed that male P. jordani, male and female P. glutinosus, and an electrophoretically distinct and non-hybridizing sympatric phenotype in the P. glutinosus complex (here called species A), all preferred female airborne odours over male airborne odours. This demonstrates that these salamanders can identify sex by means of airborne odours. Male P. glutinosus and species A both preferred conspecific female odours over heterospecific female odours in olfactometer experiments. These results suggest an important role for olfaction in the sexual and social behaviour of these salamanders, particularly as a pre-mating isolating mechanism.

This research analyses variation in the interspecific aggressive behaviour of two salamander species, Plethodon jordani and P. glutinosus , from three localities which differ in extent of sympatry, the intensity of interspecific competition and frequency of hybridization. If interspecific aggression evolved by misidentification of species, it should either (1) vary concordantly with the frequency of hybridization, or (2) be similar in all of the localities. If selection for interspecific interference has occurred, interspecific aggression should vary concordantly with interspecific competition. Misidentification can account for variation in the interspecific aggressive behaviour of P. glutinosus, P. glutinosus from all localities did not distinguish behaviourally between heterospecifics and conspecifics. In contrast, for P. jordani , results suggest that alpha-selection has occurred under conditions of strong interspecific competition. P. jordani from the locality where interspecific competition is weak were less aggressive to heterospecifics than to conspecifics, while P. jordani from two localities where interspecific competition is strong were equally aggressive to heterospecifics and conspecifics.

The effects of competition on the evolution of interspecific interference mechanisms were studied by comparing the aggressive behavior of two terrestrial salamander species from two localities that differ in the intensity of interspecific competition. Plethodon jordani and P. glutinosus are closely related, ecologically similar species that are sympatric at intermediate elevations in the southern Appalachian Mountains. Previous removal and transplant experiments showed that interspecific competition is more intense in the northeastern Great Smoky Mountains, where the species are narrowly sympatric, than in the nearby Balsam Mountains, where sympatry is broader. In laboratory encounters, P. glutinosus from the Great Smoky Mountains were more aggressive to heterospecific and conspecific intruders than were P. glutinosus from the Balsam Mountains. For P. jordani, however, the variation in interspecific and intraspecific aggressive behavior among individuals within populations was as great as the variation between populations. Alpha-selection (i.e., improved competitive ability by the acquisition of interspecific interference mechanisms) has occurred in populations of P. glutinosus under conditions of intense interspecific competition. The evolution of aggressive behavior appears to have been influenced by the intensity of intraspecific competition as well.

Much ecological theory rests on the assumption that interspecific competition is exploitative, interference playing a small role. It is argued that interference mechanisms should evolve in many situations, and an example is described of an experimentally demonstrated result of the origin of interference competition. Large numbers of individuals of Plethodon jordani from an area of intense competition with P. glutinosus were substituted for conspecifics in an area where competition was less severe. The population of P. glutinosus showed a statistically significant decrease relative to controls. Although the two species had been shown to compete with each other in the locality of this experiment, other experiments showed that they had virtually no effect on congeners in the area of intense competition. The combination of results demonstrates that α-selection (sensu Gill 1974) had taken place. Since α-selection certainly involves interference mechanisms, it is important to observe that a majority of the expe...

1. 1. In preliminary experiments, salamanders of three species ( Desmognathus ochrophaeus, Plethodon cinereus and Plethodon jordani ) required 5–11 days to complete metabolic acclimation to a constant warm temperature; the rate of oxygen consumption ( V O 2 ) decreased 16–28% during acclimation. 2. 2. Unfed animals of each species underwent cyclic exposure to 5 and 21°C at three different cycle periods (12 hr, 4–5 days, 51 days), or constant exposure to 14°C for 102 days. 3. 3. The experimental treatments significantly affected the ( V O 2 ) measured at 5, 14, 17.5 and 21°C. 4. 4. The direction and magnitude of the acclimatory effects upon ( V O 2 ) were inconsistent among species and among experimental temperatures, and resulted in little energy saving. 5. 5. The ( V O 2 ) during exposure to cyclic temperatures averaged only 83% of that during preliminary experiments, perhaps as a response to starvation.

1. We staged predatory encounters between snakes and salamanders in the laboratory. 2. Both snakes and salamanders accumulated significant quantities of lactic acid (0.3–2.3 mg/g) during predatory encounters. In a typical 14.4 min encounter, lactate concentration reached 260% of resting levels in snake predators and 880% of resting levels in salamander prey. This is one of the first demonstrations of anaerobiosis during natural ‘burst’ activity in both predator and prey. 3. Salamander responses to snake attack were surprisingly variable, and included writhing, thrashing, tail wrapping, tail autotomy, and biting. Antipredator responses were effective in nearly one third of trials. Lactate concentration was significantly correlated with duration of predatory encounters (r=0.57), snake mass, and salamander mass (Table 3). 4. Our calculations suggest that attack and ingestion of prey may cost snakes less than 1% of energy assimilated from prey.

Topographies of ipsilateral and contralateral retinal inputs to the optic tectum were studied by means of electrophysiological multi-unit recordings from the superficial layers. It was found that the nasotemporal coordinate of the visual field is represented along a rostrocaudal axis on the contralateral tectal map and along a caudorostral axis on the ipsilateral map. Electrical stimulation of one tectal hemisphere and recording of the response in the other hemisphere revealed that the ipsilateral map is most probably established by an intertectal pathway. In one tectal hemisphere, inputs from the ipsilateral eye match those from the contralateral eye if stimuli are located at a certain distance at arbitrary horizontal angles within the binocular field. This distance varied from 11.8 to 29.5 mm between the 5 individuals examined.

Homing studies were conducted with Plethodon jordani in conjunction with home range investigations in 1964 and 1965 in the mountains of North Carolina. The studies were conducted at night when the salamanders could be captured on the forest litter without disturbing the habitat. Each salamander was measured and marked by toe-clipping; only the adults were sexed. The location of each capture within the study areas was determined and recorded. Non-displacement studies revealed that adult males were usually recaptured within 20 ft (6 m), and females and juveniles within 10 ft (3 m), of their initial points of capture. Displacement studies in 1964 suggested that this species was able to home from various distances up to 500 ft (150m). Animals with prior homing experience returned more frequently from new displacement distances than did salamanders without prior homing experience. In 1965, displacements of 50 and 100 ft (15 and 30 m) showed that changes in elevation or direction accompanying displacement did not affect the animals' homing response. The per cent of the recaptured animals that homed from these displacements varied insignificantly from 60 to 90 per cent. Salamanders displaced 1000 ft (300 m) showed some capacity to home from these distances (9 per cent). The homing ability appeared to increase with the growth and maturation of the salamander, since the adults homed in significantly greater frequencies than did the juveniles. Males seemed better able to home from long distance displacements than did females. In all cases salamanders without their eyes homed in similar percentages to normal displacement animals. Eyeless males of both non-displacement and displacement groups had smaller home ranges than the males of the normal non-displacement and displacement groups. This apparent difference was not observed in the females and juveniles. Experiments concerned with bisecting the olfactory nerves were preliminary and uncontrolled. However, they gave some indication that the sense of smell is necessary in the homing response.

Competition lies at the foundation of evolution by natural selection; it is assumed to be of universal occurrence within species, and almost as frequent between distinct species. The subject of interspecies competition has recently received an excellent review by Crombie (1947), and no attempt has been made here to give a complete bibliography. The complexity of the situation in nature makes even the description of natural cases of interspecies competition difficult and therefore rare, and analysis of such cases is even more hazardous. Notable successful examples are Beauchamp and Ullyott (1932) for freshwater triclads, and Lack (1945) for birds. The laboratory experiments of Gause (1934), Crombie (1945), Park (1948), and others have yielded valuable information on the problem, but even in such oversimplified cases, little has been discovered concerning the mechanisms by which successful species achieve the demise of their competitors. There are certain obvious differences between interspecies and intraspecies competition. The former has frequently been demonstrated to lead to the elimination of one competitor when two species are confined within a limited space, all parts of which are accessible to each, and given a source of food which each can utilize. A deviation from strict adherence to these conditions may permit the two species to co-exist (cf. Crombie 1945), and the natural environment usu

1. We examined the time courses of thermal acclimation for critical thermal minima (CTMin) in the salamanders Desmognathus quadramaculatus, D. monticola, D. ochrophaeus, and Plethodon jordani. 2. D. quadramaculatus showed no annual differences in their time courses, but we noted seasonal differences in the CTMin with these salamanders having lower CTMin in the spring. 3. Gain in CTMin (25 degrees C to 5 degrees C transfer) was faster than its corresponding loss (5 degrees C to 25 degrees C transfer) in D. quadramaculatus. 4. Comparison of all three Desmognathus species revealed no differences in the CTMin for the 5 degrees C to 25 degrees C time courses, but P. jordani had lower CTMin than corresponding D. quadramaculatus. 5. Our results indicate that the pattern of CTMin acclimation correlates with the constraints acting on salamanders in their natural environment.

Using radioactive tags, we recorded movements of salamanders (Plethodon jordani) in their home areas and during homing. Males occupied home areas about three times larger than those of females and made occasional excursions into outlying regions. Homing after 22-to 60-meter displacements was direct and rapid, once initiated. Course headings at 1 meter from release were random; those at 2 meters and more were home-oriented. Males initiated homing movements sooner than females, although both sexes traveled at similar rates. Increased incidence of climbing on vegetation after displacement suggests olfactory mechanisms of orientation. These observations give direct evidence of homing orientation in caudate amphibians.

Using museum collection records and variables computed by digital terrain modeling in a geographic information system, we examined the relationship of elevation, aspect, and “cove” patch size to the presence or absence of 7 common woodland salamanders in mature cove hardwood and northern hardwood forests in the southern Appalachians of Georgia, North Carolina, and South Carolina. Overall, elevation, aspect and patch size were poor discriminators among salamander species presence or absence at collection sites. Increased elevation was an important variable explaining the presence of Ocoee salamanders (Desmognathus ocoee) and Jordan's salamanders (Plethodon jordani). In contrast, decreased elevation was an important variable explaining the presence of slimy salamanders (Plethodon glutinosus). Our study contrasts with recent research indicating that suitable habitat patch size is an important determinant of woodland salamander species richness and abundance at recently disturbed sites. In these matu...