Desmognathus Quadramaculatus Research Articles

Morphological differentiation between the larval forms of two cryptic species of dusky salamander (Desmognathus)

Desmognathus quadramaculatus and D. folkertsi are cryptic salamander species that occur sympatrically across the entire range of the latter species. However, the larval form of D. folkertsi has never been formally described, and studies of salamander larval communities within its range require the ability to distinguish it from its cryptic relative. We conducted morphometric analyses in order to compare the larval forms of these two species living in allopatry and searched for characters that may be useful in distinguishing them in the field. Larvae of D. quadramaculatus had a larger average body size than D. folkertsi, and larger specimens of the former species had redder tail fins. MANCOVA indicated significant differences in a suite of 22 morphological characters between the two species. Additional principal component analysis (PCA) and discriminant function analysis (DFA) indicated strong separation of factor and discriminant scores, respectively. Besides body size and tail-fin color, the best potential field character appears to be the forelimb length (FLL)/snout-vent length (SVL) ratio with larvae of D. quadramaculatus having a ratio above 0.2 and those of D. folkertsi having a lower ratio. However, these differences need to be confirmed in sympatry before they can be completely relied upon as useful field characters.

Morphological Variation in the Cryptic SpeciesDesmognathus quadramaculatus(Black-bellied Salamander) andDesmognathus folkertsi(Dwarf Black-bellied Salamander)

Abstract Plethodontid salamanders in general and the genus Desmognathus in particular exhibit extreme morphological conservatism and rampant homoplasy so that cryptic lineages are common. In spite of this, multivariate morphometric analysis has proven a useful tool in detecting subtle morphological differences among cryptic forms. We used this technique to investigate subtle differences in morphology among populations of Desmognathus quadramaculatus (Black-bellied Salamander) and its cryptic congener, Desmognathus folkertsi (Dwarf Black-bellied Salamander). We found significant morphological variation among five populations of D. quadramaculatus but not between two populations of D. folkertsi. We also determined there to be a significant, albeit weak, correlation between genetic distance and morphological (Mahalanobis) distance. Given the relationship between genetic and morphological distance, the high morphological variation within D. quadramaculatus, relative to that within D. folkertsi, is not surpris...

Salamander diversity alters stream macroinvertebrate community structure

Summary Salamanders are abundant consumers in many fishless stream ecosystems, but few studies have explicitly examined their ecological role. Stream‐dwelling salamander larvae are generalist predators of aquatic macroinvertebrates and may play an important role in structuring macroinvertebrate communities. The potential for emergent effects of multiple predator species suggests that changes in salamander diversity could alter their effects on macroinvertebrate communities, but this has not been tested. We used in‐stream enclosures to manipulate the presence and diversity of the two most abundant salamanders, Eurycea wilderae (EWIL) and Desmognathus quadramaculatus (DQUA), in a southern Appalachian Mountain headwater stream to examine the impacts of salamander predation on macroinvertebrate communities. We were particularly interested in testing for potential diversity effects by comparing the effects of each species in monoculture to polycultures of both species (BOTH). Salamanders reduced macroinvertebrate abundance compared to the control treatment (CONTROL), but only when both species were present together. The general pattern of macroinvertebrate abundance among treatments was: CONTROL = EWIL = DQUA > BOTH, although no treatment significantly reduced the abundance of epibenthic taxa. The BOTH treatment also significantly altered macroinvertebrate community structure and reduced taxon richness by c. 57%. The effects of salamanders were particularly pronounced for chironomids (Diptera: Chironomidae), which comprised the majority of macroinvertebrate total abundance. Increased salamander diversity substantially altered macroinvertebrate communities, suggesting that niche complementarity or facilitation occurred despite the apparent functional similarity of these two species. Therefore, changes in salamander diversity may alter the effects of salamander communities on macroinvertebrates, which may cascade through food webs to affect stream ecosystem function.

Critical Tail Autotomy for Reduction of Maximal Swimming Performance in a Plethodontid Salamander (Desmognathus quadramaculatus)

Although tail autotomy often has an immediate survival benefit, tail loss may subsequently hinder locomotion and the ability to escape from predators. Maximal locomotor performance can be reduced after tail autotomy in the plethodontid salamander Desmognathus quadramaculatus. The loss of a large proportion of the tail length (>60%) is costly for this semiaquatic species in terms of a reduction in maximal swimming performance (i.e., burst speed is about 50% less after such autotomy). However, the minimal amount of tail loss that causes a significant reduction in swimming performance (i.e., the “critical tail autotomy” for locomotion) is unknown. I examined the effect of partial tail loss (either 15% or 30% of tail length) on burst swimming performance. After the loss of about 15% of tail length in one experimental group (N = 15), burst speeds for individuals were not significantly different from preautotomy burst speeds. After the loss of about 30% of tail length in a second experimental group (N = 15), burst speeds for individuals were significantly less than preautotomy burst speeds. These results indicate that the critical tail autotomy for reduction of maximal swimming performance is between 15% and 30% of tail length. About 50% of individuals in the field (N = 69) experienced tail autotomy and most (80%) of these individuals lost more than 30% of their tails. This study shows that tail autotomy often results in a reduction in maximal swimming performance and thus a locomotor cost for individuals of this species.

Tail Length and Sexual Size Dimorphism (SSD) in Desmognathan Salamanders

Tails serve multiple functions in salamanders: energy storage, courtship, antipredator defense, and respiration. Differences in life history strategies between males and females may generate sexual size dimorphism (SSD) in tail length. However, the contribution of tail length to SSD is relatively unstudied. Because the basal member of the desmognathan salamander Phaeognathus hubrichti shows SSD in tail dimensions (females have long, thin tails compared to the shorter, thicker tails of males), we hypothesized that other desmognathans may follow the same pattern. We took standard morphological measurements, aged, and sexed 342 Desmognathus quadramaculatus (the largest species of Desmognathus) and 244 Desmognathus aeneus (one of the smallest species) to determine whether SSD in tail length followed the same pattern as in P. hubrichti. Neither Desmognathus species showed SSD in tail length and the trends were in opposite directions. Males of both species had significantly wider tail diameters than the females. Females had a significantly longer distance between limbs than did males. We also found that all three species differ in resource allocation to different body parts as they mature. This suggests that life history traits, and behavioral and ecological requirements, have a stronger influence on body size than does phylogeny in this group of salamanders.

Metagonimoides oregonensis (Heterophyidae: Digenea) Infection In Pleurocerid Snails and Desmognathus quadramaculatus Salamander Larvae In Southern Appalachian Streams

Metagonimoides oregonensis (Heterophyidae) is a little-known digenetic trematode that uses raccoons and possibly mink as definitive hosts, and stream snails and amphibians as intermediate hosts. Some variation in the life cycle and adult morphology in western and eastern populations has been previously noted. In the southern Appalachians, Pleurocera snails and stream salamanders, e.g., Desmognathus spp., are used as intermediate hosts in the life cycle. We completed a series of studies in this system examining some aspects of larval trematode morphology and first and second intermediate host use. Molecular sequencing of the 28S rDNA of cercariae in our survey placed them clearly within the heterophyid family. However, light and scanning electron microscopy revealed both lateral and dorso-ventral finfolds on the cercariae in our region, whereas original descriptions of M. oregonensis cercariae from the west coast indicate only a dorso-ventral finfold, so further work on the systematics of this group may be warranted. A survey of first intermediate host, Pleurocera proxima, from 7 streams in the region identified only M. oregonensis, virgulate-type cercariae, and cotylomicrocercous-type cercariae in the streams, with M. oregonensis having the highest prevalence, and the only type present that use amphibians as second intermediate hosts. Based on clearing and staining of 6 Desmognathus quadramaculatus salamander larvae, we found that individual salamanders could have over 600 metacercariae, which form between muscle fibers throughout the body. Histological observations suggest that the metacercariae do not cause excessive tissue damage or inflammation, and likely persist through metamorphosis, thereby transmitting potentially large numbers of worms to definitive host raccoons foraging along streams.

Ecological associations and genetic divergence in Black-bellied Salamanders (Desmognathus quadramaculatus) of the Southern Appalachian Mountains

th October. Abstract. The discovery and subsequent description of cryptic biodiversity is often chal- lenging, especially for groups that have undergone rapid lineage accumulation in the relatively recent past. Even without formal descriptions, understanding genetic diversity patterns as they relate to underlying ecological or historical processes can be important for conservation. The dusky salamanders of the genus Desmognathus, with 20 described species, comprise the second largest genus of plethodontid salamanders in the eastern United States. However, due to the presence of high genetic diversity and relatively few morphological synapomorphies, the number of species is likely to increase. For the three nominal species within the D. quadramaculatus species complex, including D. quad - ramaculatus, D. folkertsi, and D. marmoratus, we used a portion of the mitochondrial genome and nuclear markers in the form of amplified fragment length polymorphisms (AFLP) to uncover spatial patterns of genetic diversity. Within D. quadramaculatus and D. marmoratus, we uncovered four well-supported lineages with the mitochondrial sequences; phylogeographic patterns were not congruent with the AFLP data. Both sets of markers identified a clear isolation by stream distance. Using multiple regressions, we found that historical river drainages and terrestrial ecoregions explained the phylogeo- graphic patterning we observed for D. quadramaculatus .

Effect of body size on tail regeneration and recovery of swimming performance after caudal autotomy in a plethodontid salamander

I examined the effect of body size on the locomotor cost of caudal autotomy in the plethodontid salamander Desmognathus quadramaculatus. In this primarily aquatic species, larger individuals autotomize the tail less readily than smaller individuals, and this may be related to a greater locomotor cost of tail loss for larger individuals. To determine whether the rate of regeneration for tail length and the recovery of maximal locomotor performance after caudal autotomy vary with body size, I measured the rate of tail re-growth and the swimming burst speed for 14 individuals (snout-vent length = 42-106 mm) as they regenerated their tails. Burst speeds of individuals were significantly reduced after caudal autotomy. With the loss of about 62% of tail length, mean burst speed declined about 50%. Thus, caudal autotomy was costly in terms of a reduction in maximal locomotor performance in an aquatic environment. After the regeneration of 50% of the tail length that was lost, post-autotomy swimming speeds were not significantly different from pre-autotomy swimming speeds. The time required for this amount of tail length regeneration (about 63-143 d) increased significantly with body size. The rate of re-growth for the lost tail length declined significantly after the regeneration of 50% of tail length. These results demonstrate that the locomotor cost of tail loss is greater for larger individuals of D. quadramaculatus, and this may be related to a lower propensity for caudal autotomy and a greater propensity for alternative antipredator mechanisms (e.g., biting) for such individuals.

ACUTE TOXICITY OF ACIDITY IN LARVAE AND ADULTS OF FOUR STREAM SALAMANDER SPECIES (PLETHODONTIDAE)

High levels of acid deposition have severely affected streamwater chemistry in the southern Appalachians. Plethodontid stream salamanders living in and around headwater streams rely on cutaneous respiration and are highly susceptible to changes in water quality. We examined the sensitivity to low pH conditions in four stream salamanders by monitoring the response to six pH treatments ranging from pH 2.75 to 6.5. To quantify acid tolerance, we determined median lethal concentrations (LC50) in 96-h laboratory bioassays. This is the first study to quantify the level of sensitivity of stream salamanders to acidic conditions, indicating that stream salamanders are acid tolerant compared with many other lotic organisms. We found that acid tolerance is a species-specific trait with intraspecific variation shaped by life stage and body size. Mortality occurred at pH levels less than 4.2. The acid sensitivity of Desmognathus quadramaculatus larvae (LC50 = pH 3.95) was highest compared to sensitivity of Eurycea cirrigera larvae (LC50 = 3.6), Gyrinophilus porphyriticus larvae (LC50 = 3.5), and Pseudotriton ruber larvae (LC50 = 3.5). Larval survival was lower than adult survival in low pH treatments for E. cirrigera (adult LC50 = 3.1) and D. quadramaculatus (adult LC50 = 3.5). Salamanders responded to sublethal exposure to acidity with lethargic movements and decreased swimming speed. These results suggest that episodic acid events that cause streamwater pH to drop near 4.2 may cause mortality or induce sublethal effects, such as slower swimming speed. Because salamander larvae are more sensitive to acidic conditions than adults, we recommend that population monitoring programs extend methodology to include reliable estimates of larval population sizes.

Productivity and significance of headwater streams: population structure and biomass of the black‐bellied salamander (Desmognathus quadramaculatus)

Summary1. Headwater streams are a significant feature of the southern Appalachian landscape, comprising more than 70% of the total stream length in the region. Salamanders are the dominant vertebrate within headwater‐riparian forest ecosystems, but their ecological role is not clearly understood.2. We studied a population of black‐bellied salamanders (Desmognathus quadramaculatus) at a headwater stream in the southern Appalachian Mountains using radio‐telemetry and mark‐recapture methods. The length and area of headwater streams in the region were estimated using GIS.3. Home ranges of radio‐tracked salamanders were relatively small (mean = 1.06 m2). Adult salamanders in our telemetry study inhabited edge microhabitats significantly more often than either stream or riparian microhabitats, and the same trend was observed in the mark‐recapture study.4. We estimated the population density at this site to be 11 294 salamanders ha−1, amounting to 99.30 kg ha−1 of biomass, an estimate that is six times greater than reported in previous studies. The majority of this biomass was found within the stream, but 22% was found in the surrounding riparian habitat more than 1 m from the stream. Using headwater stream length and area estimates, we extrapolated biomass estimates for black‐bellied salamanders inhabiting stream and riparian microhabitats across the study region.5. We report one of the largest estimates of secondary consumer biomass for a headwater ecosystem, attesting to the overall productivity of headwater streams. Headwaters are known to be important for ecological and ecosystem processes and our biomass estimates suggest that salamanders are a critical component to these systems.

Reproductive Life History of Desmognathus folkertsi (Dwarf Black-bellied Salamander)

Abstract An earlier collection of monthly samples of presumed Desmognathus quadramaculatus from Union County, GA, revealed the presence a previously unknown, sympatric, sibling species. This new form was recently described as D. folkertsi. In this paper, we report on the reproductive life history of this new species from data taken during (1) a 14-month period in 1989–90 and (2) late spring of 1998. Adult males and females mature at approximately the same size (57–58 mm snout–vent length [SVL]), and males reach larger mean (72 versus 66 mm SVL) and maximum (81 versus 75 mm SVL) sizes. Metamorphosis apparently takes place at approximately two years of age, and reproductive maturity is reached at four or more years of age in both sexes. If number of lobes in the multi-lobed testis indicates age, as has previously been presumed in adult male Desmognathus, then the paucity of singly-lobed, presumably young male D. folkertsi in both sampling periods suggest a declining population. Relative measures of density,...

Determinants of Metamorphic Timing in the Black-bellied Salamander, Desmognathus quadramaculatus

Abstract We used two experiments to test the hypothesis that variation in growth rate, temperature, and thyroid hormone exposure will induce variation in metamorphic timing in the Black-bellied Salamander, Desmognathus quadramaculatus (Holbrook). In one experiment, second-year larvae (i.e., those approaching a metamorphic summer) were treated with high or low food and exposed to high or low temperature. Low temperature resulted in delayed metamorphosis, while food regime had no effect on metamorphic timing. In a second experiment, first-year larvae (i.e., those not expected to undergo natural metamorphosis during the experiment) were grown at two temperatures and treated with thyroid hormones or control supplements. Larvae at low temperature grew more slowly. Larvae treated with thyroid hormone failed to show any sign of metamorphosis compared to control larvae.

Antipredator Behaviors of the Red Hills Salamander, Phaeognathus hubrichti

The antipredator behaviors of Phaeognathus hubrichti (Red Hills Salamander), a large fossorial plethodontid, and the basal member of the desmognathine salamanders, are unknown. The responses of P. hubrichti to tongue-flicks from hand-held snakes, tapping with a rod and pinching with a forceps were recorded with a videocamera. When contacted by a snake tongue- flick, P. hubrichti exhibited several antipredator behaviors including immobility, gape, walk, run, head flatten, head elevation, flip, bite, and flinch. One other antipredator behavior—writhe—was observed in the field. The antipredator be- haviors of P. hubrichti are more similar to those species in its sister taxon, Desmognathus, than to those of other less closely related fossorial salamanders. Gape, a threat display, is nearly identical to that of Desmognathus quadramaculatus. Gape, bite, and writhe are proposed to be ancestral behaviors in this group.

Life History and Distribution of the Leech Oligobdella biannulata (Moore, 1900) (Euhirudinea: Glossiphoniidae)

Abstract Oligobdella biannulata is a rare, endemic leech species originally described from a mountain stream near Blowing Rock, North Carolina, U.S.A. Specimens of O. biannulata were collected seasonally (fall 1999–summer 2002), documenting new county records from North Carolina and South Carolina and new state records from Georgia and Tennessee, U.S.A. Fifty-one percent of Desmognathus quadramaculatus and 50% of Desmognathus marmoratus were parasitized with O. biannulata. Between late May and early July, O. biannulata leaves its salamander host to lay 15–30 bright yellow, yolky eggs and brood them on its ventral surface. Eggs hatch in 10–20 d, and in about 50 d both hatchlings and adult search for a blood meal. Oligobdella biannulata reattaches to its host between late August and early October. When a desmognathine salamander host is found the adult leech attaches and hatchlings leave the adult, attaching singly or in clusters on the limbs or axillary and inguinal regions of the salamander, blood feeding...

The influence of ecology and genetics on behavioral variation in salamander populations across the Eastern Continental Divide.

Understanding the unique contributions of ecology and history to the distribution of species within communities requires an integrative approach. The Eastern Continental Divide in southwestern Virginia separates river drainages that differ in species composition: the more aquatic, predatory Desmognathus quadramaculatus is present only in the New River drainage (which drains to the Gulf of Mexico), while Desmognathus monticola is present in both the New River drainage and the James River drainage (which drains to the Atlantic Ocean). We investigated natural distributions, behavioral variation in experimental mesocosms, population genetic, and phylogenetic implications of community structure. The presence of D. quadramaculatus increased the terrestriality of D. monticola in natural and experimental situations but to different degrees in allopatric and sympatric populations. Our ecological data suggest that the degree of terrestriality in D. monticola is a result of a balance between the optimal aquatic habitat and risks of predation. Our genetic analyses suggest that D. monticola has experienced a recent range expansion and has only a recent history of association with D. quadramaculatus in Virginia. This is surprising given the strong behavioral variation that exists in populations experiencing unique community compositions over a scale of meters. This study demonstrates the need to combine both ecology and genetics toward an understanding of the factors affecting species distributions, behavioral variation between populations, and patterns of genetic variation across a landscape.

Life history of a small form of the plethodontid salamander Desmognathus quadramaculatus

AbstractWe sampled Desmognathus quadramaculatus, one of the largest species of plethodontid salamanders in eastern North America, from a population exhibiting extremely small adult body sizes in the Bald Mountains of North Carolina (USA). In order to test the hypothesis that miniaturization in desmognathine salamanders is due to early metamorphosis and maturation, we estimated ages and sizes at metamorphosis and maturation. Analysis of size-frequency distributions suggests that most larvae metamorphose after 24 months, with the remainder metamorphosing after 36. The minimum age of sexually mature individuals in the summer months is estimated to be 4 years in males and 5 years in females; some may mature 1 year earlier. This is earlier than other reliable estimates of age at maturation in D. quadramaculatus, and appears to account for the small size of the species at this locality. Larval and juvenile growth rates are within the range of growth rates of other populations. As in other populations of D. quadramaculatus, males are smaller than females at maturation, but grow to larger sizes. Estimates of clutch sizes based on dissection of gravid females are relatively low. The other species of salamanders in this community do not appear to be miniaturized.

SKELETOCHRONOLOGICAL ANALYSIS OF VARIATION IN AGE STRUCTURE, BODY SIZE, AND LIFE HISTORY IN THREE SPECIES OF DESMOGNATHINE SALAMANDERS

We evaluated age structure in three species of desmognathine salamanders at Coweeta Hydrologic Laboratory, North Carolina, for comparison with the results of an earlier study of age structure in these species at a nearby locality (Wolf Creek, North Carolina). At Coweeta, both Desmognathus quadramaculatus and D. monticola attain larger adult body sizes and greater ages than their Wolf Creek counterparts. The differences appear to stem in part from greater ages at sexual maturation in both species at Coweeta versus Wolf Creek. This disparity is most pronounced in D. quadramaculatus, where the estimated ages at first reproduction are 7–8 yr in males and 9–10 yr in females. The Coweeta populations of D. quadramaculatus and D. monticola may also have higher survivorship and higher rates of post-maturational growth than those at Wolf Creek. In contrast, in the third and smallest species, D. ocoee, the Coweeta population did not differ in size and age attributes from that at Wolf Creek. We hypothesize that the m...

Differing Diel Patterns of Temperature Selection in Two SympatricDesmognathus

Despite the potential constraints imposed by cutaneous respiration and nocturnality, some salamanders actively thermoregulate when conditions permit. We measured substrate temperature selection in two species of Desmognathus in a moist thermal gradient in the laboratory. Desmognathus monticola selected significantly higher temperatures than Desmognathus quadramaculatus. Although the substrate temperatures selected by D. quadramaculatus did not vary over time (mean ± 1 SE = 13.6 ± 1.1 C), D. monticola selected significantly higher temperatures at night than during the day. Mean temperatures selected by D. monticola were 14.0 ± 1.5 C from 1200–1600 h and 19.7 ± 1.6 C from 2000–0000 h. This difference in temporal patterns is consistent with field behavior, because D. monticola is more frequently found away from water at night than is D. quadramaculatus.

Stand age and habitat influences on salamanders in Appalachian cove hardwood forests

We surveyed cove hardwood stands aged 15, 25, 50, and ≥85 years following clearcutting in the southern Appalachian Mountains of northern Georgia to assess the effects of stand age and stand habitat characteristics on salamander communities using drift-fence array and pitfall methodologies from May 1994 to April 1995. Over a 60,060 pitfall trapnight effort, we collected 3937 salamanders represented by Desmognathus aeneus, Desmognathus monticola, Desmognathus ocoee, Desmognathus quadramaculatus, Eurycea bislineata, Gyrinophilus porphyriticus, Pseudotriton ruber, Plethodon glutinosus, Plethodon serratus, and Notophthalmus viridescens. Analysis of covariance with pitfall array to stream distance as the covariate showed that salamander species richness and diversity measures and numbers of Desmognathus aeneus and Desmognathus ocoee were highest in stands ≥85 years. Eurycea bislineata and Plethodon glutinosus were more abundant in stands ≤50 years old than in stands ≥85 years. Within cove hardwood stands, species richness and diversity measures and relative abundances of Desmognathus spp. and Gyrinophilus porphyriticus were negatively correlated with distance to stream. Species richness and diversity were positively correlated to amounts of emergent rock. Species richness, diversity and relative abundances of Desmognathus spp. were correlated with basal area within stands and extent of connected mesic, cove hardwood habitat and amount of cove habitat within 1 km radius among stands. Eurycea bislineata was negatively correlated with landform index, a measure of surrounding landform sheltering, and Plethodon glutinosus was positively correlated with elevation in cove hardwood stands. Our research indicates stand age is an important factor in explaining the abundance and community composition of salamanders in southern Appalachian cove hardwood communities. Because southern Appalachian woodland salamander communities are slow to recover and are substantially changed following disturbances such as clearcutting, populations in small, isolated cove hardwood stands might be more vulnerable to extirpation or may require longer recovery times than those in larger coves. Managers may need to assess habitat features such as cove extent and habitat connectivity to minimize impacts on these taxa by forest management activities in southern Appalachian cove hardwood communities.

The Leech, Oligobdella biannulata (Glossiphoniidae) on Desmognathine Salamanders: Potential for Trypanosome Transmission?

Abstract Four species of sympatric metamorphosed desmognathine salamanders collected from southern Appalachian mountain streams in western North Carolina were examined for the presence of the glossiphoniid leech, Oligobdella biannulata. Leeches were most frequently observed on Desmognathus quadramaculatus (prevalence and mean intensity = 22.6% and 2.8 ± 2.1, respectively). The largest leech infrapopulations (≥5 leeches/host) were observed on the largest individuals of D. quadramaculatus with 45.6% of the leeches observed found on five hosts, all of which were >82 mm SVL. The larger body size and more aquatic habitat requirements of this species, relative to Desmognathus monticola and D. ochrophaeus, increases the potential for transmission of leeches. Leeches were not found on the most aquatic salamander, D. marmoratus, nor the most terrestrial congener, D. ochrophaeus. The former species inhabits strong currents in streams; a habitat possibly limiting leech attachment and prolonged feeding. Leeches showe...