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PubMed1996

Effects of dopamine and fluphenazine on field potential amplitude in the salamander olfactory bulb.

The effects of dopamine (DA) and fluphenazine (FLU), a phenothiazine DA receptor antagonist, were examined in the salamander olfactory bulb. Field potentials were recorded in the granule cell layer of superfused hemibrain preparations, and the amplitude of the large positive peak was compared following stimulation of the olfactory nerve (ON) and lateral olfactory tract (OT). In preparations superfused with normal amphibian Ringer's solution, the large peak occurred 14-21 ms after either ON or OT stimulation. It therefore appeared to reflect the activation of granule cell synapses with mitral cells, as in olfactory bulbs of other species. In three groups of preparations that were superfused with single concentrations of DA, significant decreases were observed in the amplitude of the large peak of ON- and OT-evoked potentials with increases in concentration from 5-200 microM. Moreover, with 5 microM DA and 50 microM DA, significant decreases were observed in the amplitude of the large peak of ON-evoked potentials with increases in superfusion time from 1-15 min. With each DA concentration tested, the mean percentage decrease in the ON-evoked potentials was significantly larger than the mean percentage decrease in the OT-evoked potentials. In five groups of preparations that were superfused with single concentrations of FLU, significant decreases were also observed in the amplitude of the large peak of ON- and OT-evoked potentials with increases in concentration from 0.5-150 microM. With 100 microM FLU and 150 microM FLU, significant decreases were observed in the amplitude of the large peak of both ON- and OT-evoked potentials with increases in superfusion time from 5-10 min. With each FLU concentration tested, the mean percentage change in the ON-evoked potentials was significantly larger than the mean percentage change in the OT-evoked potentials. The stronger effects of DA and FLU on the ON-evoked than OT-evoked potentials suggested that both drugs target receptors in the rostral (superficial) layers of the salamander olfactory bulb which have a higher density or affinity for DA and FLU than receptors in the more caudal (deep) layers of the bulb. When preparations were superfused with an equimolar mixture of DA and FLU at the ED50 concentrations (50 microM for both), FLU blocked approximately 50% of the decrease in the amplitude of the ON-evoked potentials relative to the decrease measured in preparations superfused with DA alone. Since FLU depressed the amplitude of ON-evoked potentials when it was tested alone, however, the rostral DA receptors could occur on both the olfactory receptor cell axons and their postsynaptic targets, or FLU could limit mitral/tufted cell excitation by affecting other types of receptors or voltage-sensitive Ca2+ channels. Results of this study which show that DA and FLU reduce the amplitude of evoked potentials in the salamander olfactory bulb provide evidence for the occurrence of DA receptors in the amphibian brain. More importantly, the stronger effects of DA and FLU on the ON-evoked than OT-evoked potentials suggest that the DA receptors could function to limit the excitation of cells at an early synaptic level in the salamander bulb. By modulating spatiotemporal patterns of synaptic activity in the glomerular layer, the receptors could profoundly influence the initial encoding of information about odors.

Ambystoma↗
PubMed2005

Energy flow and subsidies associated with the complex life cycle of ambystomatid salamanders in ponds and adjacent forest in southern Illinois.

Breeding adults and metamorphosing larval amphibians transfer energy between freshwater and terrestrial ecosystems during seasonal migrations and emergences, although rarely has this been quantified. We intensively sampled ambystomatid salamander assemblages (Ambystoma opacum,A. maculatum, and A. tigrinum) in five forested ponds in southern Illinois to quantify energy flow associated with egg deposition, larval production, and emergence of metamorphosed larvae. Oviposition by female salamanders added 7.0-761.4 g ash-free dry mass (AFDM) year(-1) to ponds (up to 5.5 g AFDM m(-2) year(-1)). Larval production ranged from 0.4 to 7.4 g AFDM m(-2) year(-1) among populations in three ponds that did not dry during larval development, with as much as 7.9 g AFDM m(-2) year(-1) produced by an entire assemblage. Mean larval biomass during cohort production intervals in these three ponds ranged from 0.1 to 2.3 g AFDM m(-2) and annual P/B (production/biomass) ranged from 4 to 21 for individual taxa. Emergent biomass averaged 10% (range = 2-35%) of larval production; larval mortality within ponds accounted for the difference. Hydroperiod and intraguild predation limited larval production in some ponds, but emerging metamorphs exported an average of 70.0+/-33.9 g AFDM year(-1) (range = 21.0-135.2 g AFDM year(-1)) from ponds to surrounding forest. For the three ponds where larvae survived to metamorphosis, salamander assemblages provided an average net flux of 349.5+/-140.8 g AFDM year(-1) into pond habitats. Among all ponds, net flux into ponds was highest for the largest pond and decreased for smaller ponds with higher perimeter to surface area ratios (r2 = 0.94, P<0.05, n = 5). These results are important in understanding the multiple functional roles of salamanders and the impact of amphibian population declines on ecosystems.

Animals↗
PubMed1988

Elimination kinetics of acetylene and Freon 22 in resting and active lungless salamanders.

To quantify diffusion limitation in cutaneous gas exchange, the elimination of two inert gases of different diffusivity, Freon 22 (CHC1F2) and acetylene (C2H2), was measured simultaneously in exclusively skin-breathing lungless salamanders, Desmognathus quadramaculatus. In resting salamanders, elimination of both gases could be described as the sum of three exponential terms. For both the medium and the slow exponential component, the ratio of the respective rate constants (k) for acetylene and Freon averaged 1.77. This value is between the values expected for perfusion limitation (1.00) and diffusion limitation (1.94), indicating combined diffusion and perfusion limitation. In salamanders stimulated to run on a treadmill, the elimination rates and the rate constants increased more for Freon than for acetylene. During spontaneous activity, the increase in elimination of Freon was larger than that of acetylene. These findings suggest an increase in the diffusing capacity of the skin during exercise. Thus the diffusing capacity of salamander skin for gases appears to be variable and to be adjusted to meet the increased O2 requirement during exercise.

Acetylene↗
PubMed1995

Hemoglobin function in a skin-breathing aquatic salamander, Desmognathus quadramaculatus.

Adult black-bellied salamanders (Desmognathus quadramaculatus) were maintained in humidified gas at 12 degrees C. Hypoxic salamanders were exposed to 8.1-9.6% O2 for 10-11 days; normoxic animals were maintained in air (20.9% O2). Hypoxia acclimation had no effect on blood O2 affinity, O2 equilibrium curve shape or CO2 Bohr effect. At pH 7.7, P50 values for hypoxic and normoxic salamanders were 28.2 +/- 0.4 and 28.6 +/- 0.8 Torr, respectively. Hill plots were curvilinear for both treatments; Hill's n increased from values of 2.1-2.2 below 40% saturation (S) to 2.6 above 50% S. CO2 Bohr slopes (delta log P50/delta pH) were -0.19 +/- 0.01 and -0.23 +/- 0.02 for hypoxic and normoxic animals, respectively. Resting MO2 for a separate group of normoxic salamanders fell into two categories; low MO2 (1.46 +/- 0.16 mumol.g-1.h-1) and high MO2 (3.51 +/- 0.52) animals. Exposures to 5 and 25% CO had no effect on MO2 of low metabolism Desmognathus, but reduced MO2 of high metabolism animals to levels similar to the low MO2 group. Hb-O2 binding results suggest that D. quadramaculatus blood is ideally suited for respiratory O2 exchange during normoxic activity. While submerged and inactive, hypoxic boundary layers surround the skin-breather. Contributions of Hb during hypoxic inactivity may be to augment O2 content and increase blood buffering capacity.

Animals↗
PubMed1987

Survival of spotted salamander eggs in temporary woodland ponds of coastal Maryland.

Temporary ponds on the Atlantic Coastal Plain in maryland were characterized according to water chemistry, rain input, phytoplankton, zooplankton and use by the spotted salamander Ambystoma maculatum during March-October 1983-1984. Neither the number of egg masses per unit of pond surface (abundance) nor the survival of spotted salamander embryos was significantly correlated (P>0.05) with pond pH. Rainfall during May-July significantly increased the hydrogen ion concentration of 5 of 11 ponds evaluated for the impact of rainfall during the previous 48h and the previous week. Survival of egg masses transferred among eight ponds with pH3.66-4.45 and one pond with pH5.18 was significantly reduced (P<or=0.05) only at pH 3.66. Embryonic survival was negatively correlated (P<or=0.05) with the concentration of aluminium in the pond water. The abundance of egg masses was positively correlated (P<or=0.05) with water temperature and magnesium concentration, and total chlorophyll during the larval period. Yearly variability of pond characteristics (e.g. water chemistry, pond longevity) and amphibian reproduction make it difficult to determine the effects of acidic deposition on the spotted salamander. At the present time, pond longevity, water temperature and possibly, oxygen content, seem more important to spotted salamander reproduction than chemical changes caused by annual acidic deposition.

Journal Article↗
PubMed1983

Distribution of monoamine oxidase activity in tissues of the urodeles Ambystoma tigrinum (tiger salamander) and Necturus maculosus (mudpuppy).

1. Monoamine oxidase (MAO) activity was determined fluorometrically in tissues of adult mudpuppies, and pre- (young) and post- (adult) metamorphic tiger salamanders. 2. From responses to specific inhibitors it was determined that 95% activity was MAO type A in all tissues. 3. In young salamanders MAO activity was greater in brain and intestine of males than of females, and was considerably higher in kidney of both sexes and in intestine of males compared to adults. 4. MAO activity was distributed differently in the mudpuppy compared to the salamander. Intestine and liver contained high activity and brain had relatively little MAO activity compared to salamander. 5. The apparent Michaelis constant of MAO activity in the different groups and tissues was generally similar, suggesting a similarity of the MAO molecule.

Aging↗
PubMed2004

Influence of physical stress, distress cues, and predator kairomones on the foraging behavior of Ozark zigzag salamanders, Plethodon angusticlavius.

An animal's response to environmentally induced stress can have important fitness consequences. For example, an animal may reduce activity in response to stress related to increased predation risk, but this response carries the potential cost of missed foraging or mating opportunities. We used laboratory bioassays to determine whether Ozark zigzag salamanders, Plethodon angusticlavius, decreased their feeding behavior following increased levels of threat-related stress. Stress level was manipulated in three experiments where salamanders were exposed to direct or indirect indicators of stress. The direct cue was a physical attack. The indirect cues were chemical cues from distressed conspecifics and chemical cues ("kairomones") from predatory ringneck snakes, Diadophis punctatus. For all three cues, stressed salamanders showed lower foraging success than unstressed salamanders. The physical attack did not result in a more intense response than the other treatments, possibly because the attack occurred away from the foraging area. The intensity of the response to stress may depend more on the nature of the threat (identity and imminence) than the level of physical disturbance.

Adaptation, Physiological↗
PubMed2006

Molecular cloning of estrogen receptor alpha (ERalpha; ESR1) of the Japanese giant salamander, Andrias japonicus.

Estrogens are essential for normal reproductive activity in females and males and for ovarian differentiation during a critical developmental stage in many vertebrates. To understand the molecular mechanisms of estrogen action and to evaluate estrogen receptor ligand interactions in the Japanese giant salamander (Andrias japonicus), we isolated cDNA encoding the estrogen receptor (ER) from the liver. A full-length Japanese giant salamander ER cDNA (jgsER) was obtained using 5' and 3' rapid amplification cDNA ends (RACE). The deduced amino acid sequence of the jgsER showed high identity to the Xenopus ERalpha (ESR1) (77.7%). We have applied both the conventional ERE-luciferase reporter assay system and the GAL4-transactivation system to characterize this receptor. In two different transient transfection assay systems using mammalian cells, the jgsER protein displayed estrogen-dependent activation of transcription. The GAL4-transactivation system showed about 10-fold greater activity of the estrogen receptor by hormone when compared to the conventional ERE-luciferase reporter assay system. Tissue distribution of ERalpha mRNA was examined and kidney, ovary and liver exhibited expression. This is the first isolation of an estrogen receptor from a salamander and also is the first functional cDNA obtained from the Japanese giant salamander, an endangered species considered a special natural monument of Japan.

Amino Acid Sequence↗
PubMed2004

Patterns of axial and appendicular movements during aquatic walking in the salamander Siren lacertina.

Most studies of salamander locomotion have focused either on swimming or terrestrial walking, but some salamanders also use limb-based locomotion while submerged under water (aquatic walking). In this study we used video motion analysis to describe the aquatic walking gait of Siren lacertina, an elongate salamander with reduced forelimbs and no hindlimbs. We found that S. lacertina uses a bipedal-undulatory gait, which combines alternating use of the forelimbs with a traveling undulatory wave. Each forelimb is in contact with the substrate for about 50% of the stride cycle and forelimbs have little temporal overlap in contact intervals. We quantified the relative timing and frequency of limb and tail movements and found that, unlike the terrestrial gaits of most salamanders, axial and appendicular movements are decoupled during aquatic walking. We found no significant relationship between stride frequency and aquatic walking velocity, but we did find a statistically significant relationship between tailbeat frequency and aquatic walking velocity, which suggests that aquatic walking speed is mainly modulated by axial movements. By comparing axial wavespeed and distance traveled per tailbeat during swimming (forelimbs not used) and aquatic walking (forelimbs used), we found lower wavespeed and greater distance traveled per tailbeat during aquatic walking. These findings suggest that the reduced forelimbs of S. lacertina contribute to forward propulsion during aquatic walking.

Journal Article↗
PubMed1998

Cloning and localization of RPE65 mRNA in salamander cone photoreceptor cells1.

RPE65 is a potential retinoid-processing protein expressed in the retinal pigment epithelium. Mutations in the RPE65 gene have been shown to cause certain inherited retinal dystrophies. Previous studies have shown that salamander cone photoreceptor cells have a unique retinoid processing mechanism which is distinct from that of rods. To determine whether RPE65 is expressed in photoreceptors, the RPE65 cDNA was cloned from a salamander retinal cDNA library. The deduced protein consists of 533 amino acids and is 85% identical to human and bovine RPE65. The RPE65 mRNA was detected in all of the single cone cells isolated from the salamander retina, as well as in the retinal pigment epithelium by RT-PCR, but not in the isolated rods. The RT-PCR products have been confirmed to be RPE65 by DNA sequencing. The results indicate that this potential retinoid processing protein is expressed in the cone photoreceptor cells but not in rods. Therefore, this protein may contribute to the unique retinoid processing capabilities in salamander cones.

Amino Acid Sequence↗
PubMed2004

Separated dental laminae are present in the upper jaw of Mesoamerican lungless salamanders (Amphibia, Plethodontidae).

Plethodontid salamander species from Northern America exhibit a single, unseparated dental lamina in the upper jaw, which consistently provides teeth for the unpaired premaxillary and the two maxillary bones. During the distinct mating season, adult males of these species bear long, monocuspid, unbladed teeth in the entire upper jaw, which are used during courtship. However, plethodontid salamander species from Southern Central America studied so far show either three separated dental laminae or a single dental lamina with three distinguishable tooth-producing parts connected by non-producing parts. These species reproduce aseasonally and sexually mature males permanently bear long, monocuspid, unbladed teeth on the premaxillary only. As the formation of these long, monocuspid teeth depends on the presence of androgen-receptors in the tooth-forming tissues, the morphological separation of the dental lamina in plethodontid salamanders from Southern Central America is very likely to be a prerequisite for a region-specific expression of androgen-receptors in the tooth-forming tissues controlling the differentiated shape formation of teeth in these species. Seven species of plethodontid salamanders from Costa Rica and Panama were examined and, in all, a tendency to exhibit three separate dental lamina in the upper jaw was found, although the morphological separation is definitive only in Bolitoglossa colonnea, B. lignicolor, B. pesrubra, B. schizodactyla and B. striatula. B. dofleini and B. marmorea show a continuous dental lamina with non-producing parts at the transitional sites between the parts associated with the premaxillary and the maxillary bones.

Animals↗
PubMedDate not supplied

Localization of substance P and GABA in retinotectal ganglion cells of the larval tiger salamander.

The present study was performed as part of a systematic examination of the transmitter specificity of neuronal populations in the larval tiger salamander retina. Backfill-labeling of ganglion cells from the optic tectum was combined with double-label immunofluorescence histochemistry to determine if substance P and GABA are localized to ganglion cell populations in the tiger salamander retina. The triple-label analysis revealed the presence of substance P- and GABA-ganglion cells in both central and peripheral regions of the retina. Substance P-immunoreactive ganglion cells comprised 2% of the total population of backfill-labeled ganglion cells, while less than 1% of backfill-labeled ganglion cells expressed GABA immunoreactivity. Ganglion cells were not found to co-label for both substance P and GABA. Backfill-labeled displaced ganglion cells, which comprised 1.4% of the ganglion cell population, were not observed to be immunoreactive for either substance P or GABA. Forty-six point nine percent of substance P-cells in the ganglion cell layer were backfill-labeled and were identified as ganglion cells. GABA ganglion cells comprised less than 1% of GABA-immunoreactive cells in the ganglion cell layer. Therefore, the present study provides evidence for the presence of small populations of substance P- and GABA-ganglion cells in the larval tiger salamander retina. These observations suggest a functional diversity in the population of tiger salamander ganglion cells relative to their unique transmitter specificities.

Ambystoma↗
PubMedDate not supplied

Colocalization of glycine in substance P-amacrine cells of the larval tiger salamander retina.

The present study was performed as part of a systematic examination of glycine's coexistence with other classical transmitters and neuropeptides in neuronal populations of the larval tiger salamander retina. Substance P immunocytochemistry was combined with either glycine immunocytochemistry or autoradiography of glycine high-affinity uptake to examine whether tiger salamander substance P-amacrine cells express these glycine markers. Double-label analyses revealed two populations of substance P-amacrine cells that express glycine immunoreactivity and glycine high-affinity uptake. The large majority of double-labeled cells were situated in the innermost cell row of the inner nuclear layer, while a smaller number were located in the inner nuclear layer in the second cell row distal to the inner plexiform layer. Double-label immunocytochemistry revealed that these double-labeled cells accounted for 91.7% of substance P-immunoreactive amacrine cells. A slightly lower percentage (90.1%) of substance P-amacrine cells were found to exhibit a glycine high-affinity uptake mechanism. Substance P-amacrine cells that did not co-label for markers of glycine activity were situated in the innermost cell row of the inner nuclear layer. Substance P-immunoreactive displaced amacrine cells were not observed to co-label for either glycine immunoreactivity or glycine high-affinity uptake. The present study reveals that the large majority of substance P-amacrine cells in the larval tiger salamander retina co-express markers of glycine activity. This finding suggests a functional diversity in the population of tiger salamander substance P-amacrine cells relative to their coexisting relationship with a major inhibitory neurotransmitter.

Ambystoma↗
PubMedDate not supplied

GABA(A) receptor binding and localization in the tiger salamander retina.

Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the retina and also appears to act as a trophic factor regulating photoreceptor development and regeneration. Although the tiger salamander is a major model system for the study of retinal circuitry and regeneration, our understanding of GABA receptors in this species is almost exclusively based on the results of physiological studies. Therefore, we have examined the pharmacological binding properties of GABA(A) receptors and their anatomical localization in the tiger salamander retina. Radioligand-binding studies showed that specific 3H-GABA binding to GABA(A) receptors was dominated by a single high-affinity binding site (Kd = 15.6+/-6.9 nM). Specific binding of 3H-GABA was almost completely eliminated by muscimol (Ki = 105+/-62 nM) and bicuculline (Ki = 14.3+/-2.2 microM); however, SR-95531 only displaced about 40% of specific 3H-GABA binding (Ki = 35.0+/-3.8 nM). These data indicate that there are at least two subtypes of GABA(A) receptors present in the salamander retina that can be distinguished by their antagonist binding properties: one sensitive to both bicuculline and SR-95531, and one sensitive to bicuculline but insensitive to SR-95531. Because localization of GABA receptors in the salamander retina by immunocytochemistry is problematic, GABA(A) receptors were localized by fluorescent ligand binding combined with immunocytochemical labeling for cell specific markers. Binding of fluorescently labeled muscimol to GABA(A) receptors was present in both plexiform layers and on photoreceptor cell bodies. GABA(A) receptors in the outer plexiform layer were localized to both photoreceptor terminals and horizontal cell processes.

Ambystoma↗
PubMed2000

Structure and evolution of supernumerary chromosomes in the Pacific giant salamander, Dicamptodon tenebrosus.

We examined the genetic make-up and plausible origins of the supernumerary (B) chromosomes of the Pacific giant salamander, Dicamptodon tenebrosus, from the Pacific Northwest of North America. These salamanders have variable numbers of B chromosomes, from 0 to 10 per individual. Salamanders from the most southerly and northerly regions of the species' range have lower average numbers of B chromosomes than salamanders in the middle of the range. To assess how the supernumerary chromosomes originated in D. tenebrosus, B chromosome DNA was isolated by microdissection and amplified by degenerate oligonucleotide-primed PCR. The B chromosome DNA hybridized similarly to genomic DNA from individuals of D. tenebrosus and the related species D. copei and D. ensatus, thus demonstrating that the supernumerary chromosomes were derived from the normal chromosome complement. Unique hybridization bands in both D. copei and D. tenebrosus suggest that the shared sequences have evolved independently.

Animals↗
PubMed1997

Maintenance of the Adh polymorphism in Ambystoma tigrinum nebulosum (tiger salamanders). I. Genotypic differences in time to metamorphosis in extreme oxygen environments.

Populations of gilled tiger salamanders (Ambystoma tigrinum nebulosum) living in ephemeral ponds were studied in order to determine what evolutionary processes might be affecting genetic variation at the alcohol dehydrogenase (Adh) locus. Ponds frequently dried in late summer; salamanders that did not metamorphose and leave drying ponds died of desiccation. Low levels of water oxygen significantly slowed metamorphosis of tiger salamanders in both natural and laboratory populations. Adh- SS frequency was significantly positively correlated with daily oxygen maxima in ponds, Adh-FF frequency demonstrated a nonsignificant trend to be negatively correlated with this measure, and Adh-SF frequency was unrelated to pond oxygen. Genotype frequency changes across the season in hypoxic and supersaturated ponds suggested that differential mortality of genotypes might explain the relationships with pond oxygen, although other mechanisms cannot be ruled out. Individuals of the Adh-SS genotype metamorphosed more slowly in hypoxic water than in normoxic water in the laboratory, and Adh-FF individuals metamorphosed more slowly in supersaturated water in the field, and in hypoxic water in the laboratory, than they did in normoxic water. Adh-SF individuals metamorphosed at the same rate in all oxygen environments. These data suggest that the Adh polymorphism in tiger salamanders is being maintained by selection for Adh or for a linked locus through differential metamorphosis in extreme oxygen environments.

Journal Article↗
PubMed1994

Cell size predicts morphological complexity in the brains of frogs and salamanders.

The morphological organization of the brain of frogs and salamanders varies greatly in the degree to which it is subdivided and differentiated. Members of these taxa are visually oriented predators, but the morphological complexity of the visual centers in the brain varies interspecifically. We give evidence that the morphological complexity of the amphibian tectum mesencephali, the main visual center, can be predicted from knowledge of cell size, which varies greatly among these taxa. Further, cell size is highly correlated with genome size. Frogs with small cells have more complex morphologies of the tectum than do those with large cells independent of body and brain size. In contrast, in salamanders brain-body size relationships also are correlated with morphological complexity of the brain. Small salamanders with large cells have the simplest tecta, whereas large salamanders with small cells exhibit the most complex tectal morphologies. Increases in genome, and consequently cell size, are associated with a decrease in the differentiation rate of nervous tissue, which leads to the observed differences in brain morphology. On the basis of these findings we hypothesize that important features of the structure of the brain can arise independently of functional demands, from changes at a lower level of organismal organization--in this case increase in genome size, which induces simplification of brain morphology.

Animals↗
PubMed2000

Biodiversity of Costa Rican salamanders: implications of high levels of genetic differentiation and phylogeographic structure for species formation.

Although salamanders are characteristic amphibians in Holarctic temperate habitats, in tropical regions they have diversified evolutionarily only in tropical America. An adaptive radiation centered in Middle America occurred late in the history of a single clade, the supergenus Bolitoglossa (Plethodontidae), and large numbers of species now occur in diverse habitats. Sublineages within this clade decrease in number from the northern to southern parts of Middle America, and in Costa Rica, there are but three. Despite this phylogenetic constraint, Costa Rica has many species; the number of salamander species on one local elevational transect in the Cordillera de Talamanca may be the largest for any such transect in the world. Extraordinary variation in sequences of the mitochondrial gene cytochrome b within a clade of the genus Bolitoglossa in Costa Rica reveals strong phylogeographic structure within a single species, Bolitoglossa pesrubra. Allozymic variation in 19 proteins reveals a pattern largely concordant with the mitochondrial DNA phylogeography. More species exist than are currently recognized. Diversification occurs in restricted geographic areas and involves sharp geographic and elevational differentiation and zonation. In their degree of genetic differentiation at a local scale, these species of the deep tropics exceed the known variation of extratropical salamanders, which also differ in being less restricted in elevational range. Salamanders display "tropicality" in that although speciose, they are usually local in distribution and rare. They display strong ecological and physiological differentiation that may contribute importantly to morphological divergence and species formation.

Altitude↗