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Populations ascribed to Dendrobates pumilio, the Strawberry Poison Frog, show extreme variation in color and color pattern among island and mainland locations in the Bocas del Toro Archipelago in Panama. Previous analyses indicate that these different populations are probably members of a single species. Here we present data on crosses between several different color and color pattern morphs. Successful crosses were made between different morphs from seven populations: Bocas Island, Nancy Cay, Pope Island, Bastimentos Island, and Almirante, Rambala and the Aguacate Peninsula on the mainland. The resulting offspring were characterized for color and color pattern. Our study indicates that different color morphs can interbreed to produce viable offspring. The offspring typically displayed a mixture of colors but always showed color pattern if one parent showed color pattern. This suggests that color pattern is under single locus control with dominance, whereas coloration may be under polygenic control, or may represent a single locus system with incomplete dominance.
Body size is an important variable used in life-history and sexual selection theory to predict reproductive, behavioral, and ecological traits. Except for the presence of special skin glands in males, sexual dimorphism has not been reported in the Red Hills Salamander (Phaeognathus hubrichti), the basal member of the Desmognathinae. These data provide insight into the evolution of SSD (sexual size dimorphism) in the entire subfamily. We conducted multivariate and univariate tests on eight morphological measurements of 92 preserved P. hubrichti. We also examined specimens for broken tails and U-shaped scars, which may indicate bites from conspecifics. Male salamanders were larger than females in all measurements except tail length and had more scars than either females or juveniles. This species exhibited male-biased SSD in shape and size: males were broad and bulky, females were long and thin. Regression analysis showed differences in resource allocation between male and female salamanders. Differences in life-history strategies and sexual selection in the form of male-male combat may explain these differences in body size.
The diversity and distribution of Pacific island iguanas were altered drastically following human colonization around 2800 years ago. A giant iguana recovered from archaeological sites in the Ha'apai group of islands, Kingdom of Tonga, became extinct within a century of human arrival. We describe this iguana as a new species of Brachylophus, a genus with two small arboreal species found today in Fiji (Brachylophus fasciatus, Brachylophus vitiensis) and parts of Tonga (Brachylophus fasciatus). Additional evidence suggests that B. fasciatus was probably introduced to Tonga (the type locality) by prehistoric people 2000 years after extinction of the giant form. Lapitiguana impensa, described in 2003 from Fiji by G. K. Pregill and T. H. Worthy was an even larger extinct iguana that also succumbed to human impact. The two living species are relicts of a much richer evolutionary history than previously known.
I designed laboratory and mesocosm experiments to test the hypotheses that consumption of a congener as supplemental food can increase the size variance, size, aggression rates, and mortality of intraguild predator populations. Experimental populations of Marbled Salamander (Ambystoma opacum), Jefferson Salamander (Ambystoma jeffersonianum) and Tiger Salamander (Ambystoma tigrinum) larvae that were initially fed a smaller congener Spotted Salamander (Ambystoma maculatum) as a food supplement developed larger SVL and size variation after seven days than control larvae that were not fed a congener. Experimental treatment populations had greater initial size variation because some larvae ate a congener and others did not. Treatment larvae had increased SVL, aggression rates and mortality after 60 days compared to control populations. These results suggest that intraguild predation on a congener can affect fitness and population dynamics of predator populations. I hypothesize that intraguild predation on congeners results in size variation and then increased aggression and mortality caused by cannibalism.
The reproductive modes for Smilisca puma, Smilisca sila, and Smilisca sordida are reported for the first time. Smilisca puma has the generalized reproductive mode of anurans with eggs deposited as a surface film in lentic water. Smilisca sila and S. sordida have the basin construction reproductive mode. Smilisca sila constructs an open depression and deposits eggs within the depression. Basins of S. sordida consist of three types: (1) basins with eggs attached to the substrate (AE); (2) basins with eggs floating on the surface of the water (FE); and (3) eggs buried beneath the substrate. Length of AE basins was, on average 10% longer than FE basins. The area in which eggs were buried was about 1.5 times greater in basins with buried eggs than other basins. Eggs of S. sordida are also deposited in streams indicating that basin building is a facultative behavior for this species. The frequency of basin types varied spatially and temporally during the reproductive season. More basins were constructed on islands than on stream banks. Open basins were the most common type of basin observed during the middle of the reproductive season, whereas eggs deposited in the absence of basins only occurred at the beginning of the reproductive season.
We compared activity, diving behavior and response to prey by Dermochelys coriacea and Chelonia mydas during their first 8–10 weeks of development. We reared juveniles in the laboratory and, at two-week intervals, released them in the ocean for a brief trial. Each turtle towed a device used to measure its dive profile. All turtles swam throughout their trials, but D. coriacea swam more slowly than C. mydas. Dermochelys coriacea dives had V-shaped profiles and older turtles made longer and deeper (up to 18 m) dives than younger turtles. Chelonia mydas dives were usually shallow (<6 m) and consisted of three (V, S, and U) profiles. Older C. mydas made dives that were longer but only slightly deeper than those of younger turtles. Dermochelys coriacea fed throughout the water column exclusively on gelatinous prey Aurelia, ctenophores, and unidentified gelatinous eggs. Chelonia mydas fed near the surface on floating Thalassia and Sargassum or at shallow depths on ctenophores and unidentified gelatinous eggs but ignored large jellyfish (Aurelia). Thus, early in development the two species overlap in foraging area and in diet. However as D. coriacea grow they dive deeper where prey assemblages probably differ from those in shallow water where C. mydas feed. These distinct behavioral trajectories probably cause the niches of D. coriacea and C. mydas to separate spatially very early in their development.
Abstract.—A new snake of the genus Tantilla is described from southern Belize. This species, a member of the taeniata group, is characterized by a dark gray-brown, almost black ground color; a narrow pale middorsal stripe confined to the vertebral scale row; a narrow pale lateral stripe on adjacent thirds of the third and fourth scale rows; a broad pale nape band that is complete medially; dark mottling on the lateral edges of the ventrals; and 153 ventrals 64 subcaudals in the single known specimen, a female. It is most similar to Tantilla impensa of southern Chiapas, the central Guatemalan ranges and western Honduras but differs from this species in its darker overall color pattern, the presence of dark mottling on the lateral edges of the ventrals, and in having a lower number of ventrals.
Abstract.—A new species of Echinosaura, Echinosaura brachycephala, is described from two localities on the Pacific versant of the Ecuadorian Andes. The new species differs from all other species of the genus by its conspicuously short head with a high domed snout in lateral profile and various scalation characteristics including the number of ventral scales per caudal segment, the arrangement of dorsal body scales, and a reduced or absent postmental scale. A key to the species of Echinosaura and Teuchocercus is provided.
Female salamanders in the suborder Salamandroidea store sperm in cloacal glands called spermathecae. Scanning electron microscopy was used to study these glands in females of the Southern Torrent Salamander, Rhyacotriton variegatus (Rhyacotritonidae), from northern California. Sperm initially enter the cloaca in a tangled mass from the spermatophore cap, but within the spermathecal tubules, small groups become aligned along their long axes. Sperm nuclei typically are embedded in apical microvilli of the secretory cells forming the distal acini of the spermathecae. Junctional complexes between apices of adjacent epithelial cells are occasionally broached or otherwise absent, and sperm can be found in the intercellular canaliculi between such cells. Spermathecae of R. variegatus are simple glands that branch off a tube extending dorsally into cloacal tissue. This spermathecal anatomy is in-between that of the Plethodontidae, which have a compound tubuloaveolar gland as the single spermatheca, and other salamandroids, in which sperm storage occurs in numerous simple tubular glands, each one a spermatheca. Sperm associations in the simple spermathecae of R. variegatus, however, are most similar to those reported for plethodontids.
Previous studies have shown both prolonged and plastic cycles in viviparous females of the genus Liolaemus (Iguania: Liolaemidae) from the cold temperate climate of Patagonia. Males have shown interspecific variation in the duration of the breeding season, ranging from continuous to annual. Both cycles are far different from the reproductive cycles previously described for lizards from temperate climates. I examined maximum juvenile size, growth, sexual dimorphism, male and female reproductive cycles, and litter size of viviparous Phymaturus patagonica (Iguania: Liolaemidae), a species restricted to rock promontories in the Patagonian steppe. The reproductive cycle in males is annual with spermatogenesis beginning in December and peaking in early spring of the next year. Spermatozoa are stored in the epididymides for at least two months until mid-January. In contrast, females have a biennial cycle. Thus, prolonged female cycles and large interspecific differences in male cycles characterize viviparous lizards from Patagonia.
The postsupraocular, a small oblique scale just posterior to the supraoculars and medial to the pretemporal scales, is a derived character within the taxonomically difficult Sphenomorphus group of lygosomine skinks. This character occurs in 22 of the approximately 125 described species of Sphenomorphus currently recognized. The species with this distinctive character occur in the southern Philippine Islands, New Guinea, and the Solomon Islands and are called, informally, the Sphenomorphus maindroni group. A new species in the group is described from New Guinea, where most of the species occur. A key to the species with the distinctive character is provided.
Generalist species are often both widely distributed and abundant. They also are often plastic in their ecology, both spatially and temporally, in response to variation in resources. Here, we study the food habits of the widespread European Grass Snake, Natrix natrix, in Kent in southeastern England. As elsewhere in their range, Grass Snakes at our study site mainly ate anurans (63%); however, small mammals also were fairly common in the diet (25%) and fish (10%) and birds (1%) were taken occasionally. About 65% of prey eaten by snakes were swallowed headfirst, but orientation of prey during ingestion varied among prey types. Although anurans are the major prey of Grass Snakes, the predominant species in their diet varies geographically, presumably in relation to availability; at our site, the most frequently eaten species (63%) was the introduced Marsh Frog, Rana ridibunda, which is very common and possibly influences abundance of snakes. We obtained few data on feeding habits of small snakes (< 400 mm SVL) but found anuran prey in the smallest snake in our sample; other prey types were eaten by larger snakes and therefore presumably are added to the diet as snakes grow. Maximum size of prey increased with snake size, but large snakes nonetheless continued to eat small prey as well. However, because Grass Snakes are sexually dimorphic (females larger), such size effects may be confounded with sex effects. Snakes had food in their stomachs less frequently in midsummer than they did in early and late summer. Nonetheless, even after adjusting for such seasonal variation, gravid females contained food less frequently than nongravid females. Thus, gravid females of this oviparous species apparently exhibit an anorexia similar to that seen in pregnant females of many viviparous species.
The Shenandoah Salamander (Plethodon shenandoah), known from isolated talus slopes on three of the highest mountains in Shenandoah National Park, is listed as state-endangered in Virginia and federally endangered under the U.S. Endangered Species Act. A 1999 paper by G. R. Thurow described P. shenandoah-like salamanders from three localities further south in the Blue Ridge Physiographic Province, which, if confirmed, would represent a range extension for P. shenandoah of approximately 90 km from its nearest known locality. Samples collected from two of these three localities were included in a molecular phylogenetic study of the known populations of P. shenandoah, and all other recognized species in the Plethodon cinereus group, using a 792 bp region of the mitochondrial cytochrome-b gene. Phylogenetic estimates were based on Bayesian, maximum likelihood, and maximum parsimony methods and topologies examined for placement of the new P. shenandoah-like samples relative to all others. All topologies recovered all haplotypes of the P. shenandoah-like animals nested within P. cinereus, and a statistical comparison of the best likelihood tree topology with one with an enforced (Thurow Shenandoah P. shenandoah) clade revealed that the unconstrained tree had a significantly lower –ln L score (P < 0.05, using the Shimodaira-Hasegawa test) than the constraint tree. This result and other anecdotal information give us no solid reason to consider the Thurow report valid. The current recovery program for P. shenandoah should remain focused on populations in Shenandoah National Park.
A new species of Scinax is described from Venezuela. It is the only species known from the Venezuelan Andes, between 600 and 1700 m. It differs from other species in the genus by its yellow coloration in life, two dorsolateral stripes, and unpatterned posterior surfaces of thighs. A description of the call is provided. The new species is not assigned to any species group.
The Trelew Member of the Sarmiento Formation (early Miocene) at Gaiman, Chubut province, Argentina, is one of the most prolific South American Cenozoic localities for squamatan remains. Within the lizards, at least three teiids have been cited, but the material has never been described. In this paper, mainly fragmentary dentaries and maxillae from this site are identified as belonging to the genus Tupinambis. These constitute the earliest record of this extant teiid genus. Tupinambis has a wide range of distribution through South America but is presently absent in the Gaiman area. Its occurrence in the early Miocene of Patagonia indicates warmer and more humid climatic conditions than today.
Experimentally elevated testosterone has been shown to increase the daily activity period of free-ranging lizards, but it is unknown whether the effect depends upon additional factors present in nature (i.e., conspecific interactions) or whether it can be elicited in the laboratory. In a relatively simple laboratory environment, male Mountain Spiny Lizards (Sceloporus jarrovi) implanted with testosterone had significantly greater activity levels throughout the day than sham-implanted males. Differences were greatest during the morning and late afternoon, with testosterone-treated males more likely to be out earlier and to stay out later. This general result was repeated in both spring and fall experiments using separate groups of males. Although testosterone-treated males were more active (i.e., out in the open) than control males, there was not a significant difference in the frequency of movements (>20 cm), nor did the groups differ in selected body temperature in their home cages. Nonetheless, testosterone-implanted males lost significantly more body mass than controls over the course of the experiments. Because the effect of testosterone on daily activity period occurs in the laboratory as well as in the field, it is suggested that the effect is not dependent upon interactions with complex environmental stimuli.
The first shed skins from the same clutch of neonate Corn Snakes (Elaphe gutatta gutatta) and the shed skin of conspecific adults were extracted sequentially with hexane, dichloromethane, and methanol. These solvents extracted more mass from neonate shed skins compared to adults. Gas chromatography of the hexane extract, after saponification of the lipids, showed that the percent of cholesterol was greater in shed skins from neonates, whereas many of the fatty acids were found in greater amounts from adults shed skins. These data show that the first shed skin of Corn Snakes is biochemically different from adults.
Considering the breadth of research evaluating amphibian population declines and the lack of natural history information on this invasive frog species, we identified prey items in the diet of Rana berlandieri in south and west Texas. During 2000, adult frogs were collected in the spring and fall from each of five sites in Texas: (1) Santa Ana; (2) Lower Rio Grande Valley National Wildlife Refuge complex; (3) near Falfurrias; 4) a privately owned ranch in south Texas; and (5) Big Bend National Park. In total, the stomach contents of 85 frogs were analyzed. Prey items identified indicate that individuals of this species, like other Ranids, are generalist, opportunistic predators whose diet is most strongly influenced by prey availability.
The three members of the Malagasy genus Aglyptodactylus (Aglyptodactylus madagascariensis, Aglyptodactylus laticeps, Aglyptodactylus securifer) form, together with Laliostoma labrosum, the subfamily Laliostominae within the Mantellidae (Ranoidea: Anura). In this paper, the morphology, life history, and ecology of sympatric tadpoles of A. laticeps and A. securifer are described and compared to those of A. madagascariensis and L. labrosum. Tadpoles of all Aglyptodactylus species are morphologically more similar to each other than to L. labrosum. However, all species differ with respect to habitat, feeding habits, and life history.
Most studies that examined effects of caudal autotomy on lizards focused on adults and largely neglected the potential for contrasting effects in newborns and juveniles. We examined the impact of tail autotomy on locomotor performance and growth in newborn Metallic Skinks, Niveoscincus metallicus. Two siblings were randomly selected from each of 12 litters, with one assigned to a control group (tail intact) and the other to an experimental group (tail removed). Removal of the tail at the base 24 h after birth resulted in a significant decrease in sprint speed 72 h after birth (approximately 50% reduction compared to speed within 24 h of birth). This impairment is substantially greater than that observed previously in adults of this species (35%). However, caudal autotomy at birth did not inhibit growth, measured as the increase in snout–vent length, during the first eight weeks of life. Despite maintaining growth rate, newborns were still able to regenerate at least one-third of their tail over the eight weeks of the study. We discuss how the absence of the tail, the presumed energetic cost of tail replacement, and the lack of caudal fat stores, may influence the ability of newborn N. metallicus to survive their first winter.
Eastern Fence Lizards (Sceloporus undulatus) in middle Tennessee are commonly parasitized by chiggers (Acari: Trombiculidae), but little is known about the ecological significance of this host-parasite system. Thus, I sampled S. undulatus and their habitats monthly to determine the seasonal pattern in chigger abundance and infestation intensity. Chigger abundance was low (mean = 1.8 chiggers) in the spring (April and May), eightfold higher throughout the summer, and declined sixfold in the fall (September and October). In general, infestation intensities on S. undulatus (males, females, and juveniles) followed the same pattern except that mean infestation intensity of males declined during the summer in spite of persistently high chigger abundance. The results of this study suggest that seasonal changes in chigger abundance are a major factor influencing infestation intensities on S. undulatus.
We describe the tadpole of Physalaemus albonotatus (Anura, Leptodactylidae), from specimens collected from northeastern Argentina. The distinguishing characteristics (Stage 36) are (1) labial tooth row formula: 2(2)/3(1); (2) rostral gap about 2.5 times greater than mental gap; (3) body length of 10.00 mm and total length of 24.20 mm; and (4) body dark brown to dark green dorsally with scattered dark spots. Morphological features were compared with other tadpoles belonging to the Physalaemus cuvieri species group from Argentina.
Previous toxicological and immunology assays have strongly suggested that a neurotoxic component is present in the venom of the Tiger Rattlesnake, Crotalus tigris. However, there has been no direct identification of this neurotoxin. We obtained 18 blood samples from Arizona C. tigris and analyzed them by PCR and DNA sequencing using primers specific for the acidic and basic subunits of Mojave toxin. All 18 samples demonstrated the presence of both subunits. Venom collected from five of the 18 snakes that provided blood samples were additionally tested for the presence of Mojave toxin with monoclonal antibodies. These anti-Mojave toxin antibodies recognized all five venoms. We conclude that, at least for the Arizona snakes sampled, the neurotoxin in C. tigris is Mojave toxin. Additional sampling and testing is necessary to determine the complete geographic distribution of Mojave toxin and Mojave toxin subunits in C. tigris populations.
Establishing the ancestral area of a taxon is a central theme of historical biogeography. We used the cladistic method of ancestral area analysis devised in 1992 by K. Bremer to determine the ancestral area of rattlesnakes (genera Crotalus and Sistrurus). We then extended this approach to determine the vegetation type of the ancestral area. The most probable ancestral area of rattlesnakes is the Madrean Occidental. The most probable vegetation of the ancestral area was pine-oak forest. Knowledge of the ancestral area and its vegetation was applied to macroevolutionary hypotheses regarding the evolution of the rattlesnake rattle.
Juvenile male Collared Lizards (Crotaphytus collaris) have orange, dorsolateral color patterns that closely resemble those of gravid, adult females, and it has long been hypothesized that they serve as a form of female mimicry, reducing aggression from adult males. We experimentally tested this hypothesis by painting juvenile males to remove or maintain orange coloration and measuring the agonistic response of adult males but found no significant differences between treatments. These results do not support the hypothesis that orange coloration of juvenile male Collared Lizards is used as a form of female mimicry to reduce aggression from adult males.