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Evolutionary and ecological theory generates testable predictions concerning the effects of species interactions on ecological, behavioral, and morphological traits. Throughout Ohio, two closely related and ecologically similar salamander species, Plethodon cinereus and P. electromorphus, occur in similar habitats and in many localities are found in sympatry. Geographic and behavioral patterns previously described between these two species could be the result of interspecific competition, a hypothesis that also predicts distinct patterns of resource use, morphological variation, or both when the two species occur in sympatry. Here we tested these predictions by examining patterns of resource use and morphology in sympatry and compared them to patterns observed in allopatric populations of each species. We found that morphological differences in head shape between species were location-specific, with morphological divergence occurring at some sympatric locations and convergence occurring at others. The degree of food-use overlap was also variable between locations but, in general, the two species used similar food resources.
The Rainbow Frog Scaphiophryne gottlebei lives within the humid canyons that cross the Isalo Massif, central-southern Madagascar. Knowing that a single haplotype dominates the largest part of its distribution range raised questions about the dispersal ability of the species. We affixed external radio transmitters to 36 individuals of S. gottlebei to understand whether the adults of this species actively displaced from the canyon they inhabit. We studied 13 males and 7 females in 2009 and 7 males and 9 females in 2011 over two periods (November–December 2009 and January–February 2011). Study sessions were chosen due to the different meteorological conditions: the first is the beginning of the rainy season, which corresponds to the start of reproduction; and the second being the end of the rainy season, which corresponds to a wetter period during which individuals are more likely to be feeding in order to increase body weight. Our results revealed that there is no significant difference in the activity patterns between sexes and that rain and temperature stimulate the dispersal rate. The distance covered by the individuals did not differ between males and females; the range varied from a few centimeters to approximately 50 m, although two individuals displaced more than 100 m in a single day. These data suggest that individuals of this species are quite phylopatric to the canyons they inhabit. The generalized haplotype sharing observed might then be explained by passive dispersal of larvae and metamorphosed individuals during the intense cyclonic floods.
Frogs and toads have species-specific repertoires of vocalizations that function in contexts related to reproduction. Although some 6000 anuran species have been described to date, we have comparatively few descriptions of their vocalizations, which are among their most conspicuous behaviors. Statistical descriptions of vocal repertoires are key to understanding the evolution of frog communication systems and play potentially important roles in anuran conservation and systematics. The primary objective of this study was to describe the vocal repertoire and calling behavior of the Ponmudi Bush Frog, Raorchestes graminirupes, a recently described species endemic to the Western Ghats of India. A secondary objective was to investigate patterns of individual variation in calling behavior and several potential sources of that variability, including temperature, body size, and physical condition. We analyzed 1000 calls from 25 males near Ponmudi in the State of Kerala. Males produced two distinct, pulsatile call types that were temporally organized in a hierarchical structure of short call groups and longer call bouts. The two call types differed primarily in call duration, amplitude envelope, and the number of pulses per call. The dominant frequency of both call types was significantly negatively correlated with body length, mass, and condition. Temporal properties were generally unrelated to male phenotype, and few call properties were related to temperature in our sample of recordings. Based on coefficients of variation (CV), dominant frequency exhibited less variability within and among individuals (CV ≤ 4%) compared with temporal properties (e.g., 10% < CVs < 30%). We discuss these results in relation to previous studies of vocal repertoires and call variability in other anurans.
We describe a pentaploid froglet (LLLRR; three Pelophylax lessonae and two Pelophylax ridibundus genomes) that has never been reported before within the Water Frog (Pelophylax esculentus) hybrid complexes. The pentaploid specimen was found among almost all triploid siblings obtained from a diploid female P. esculentus (LR) crossed with a diploid male P. lessonae (LL). We confirmed ploidy levels of the parents and the offspring by karyotyping, microsatellite analysis (18 loci), and measurements of DNA content and erythrocyte size. Microsatellite analysis indicated that the pentaploid originated from a tetraploid ovum (LLRR) fertilized by a haploid sperm (L). Surprisingly, the erythrocytes of the pentaploid were not proportionally larger than in triploids, despite a higher DNA content. Only 6.7% of the erythrocytes were distinctly large, whereas the others varied strongly in shape and size; besides typical ovoid mature erythrocytes there were small, tear-shaped, or enucleated ones. We discuss the possibility of loss of some cytoplasm by large erythrocytes as a result of mechanical damages during circulation through the narrow vessels; when the erythrocytes achieve a relatively higher surface-to-volume ratio, they may function more effectively in a proper gas exchange.
Demographic models identify whether animals are vulnerable to local extirpation, but including all ecological parameters across life history stages may be impeded by practical difficulties. When processes acting on certain life stages cannot be measured, extrapolations are often made. A previous study documented that the range of the turtle Myuchelys georgesi is restricted to the Bellinger River, New South Wales, Australia, and its population is stable. We assessed whether M. georgesi selects certain habitats by comparing their distribution among different water holes. We assessed the threat of catfish predation by examining the stomach contents of catfish specimens. We then evaluated whether threats to M. georgesi were likely to have been underestimated by extending our previous demographic model. We did this by revising the previous estimates of adult, juvenile, and hatchling survivorship under hypothetical variations in water hole use and in the presence or absence of catfish predators. We found that M. georgesi preferentially uses moderate to deep water holes. We also found that although catfish 250−400 mm consume hatchling or juvenile turtles, those > 400 mm do to a greater extent. By making observations of catfish in the Bellinger River and incorporating their presence into our model, we found catfish presence to influence juvenile, but not adult, water hole use. Our reassessment of λ suggests that it may have been previously underestimated and that the threat to M. georgesi may be greater than we thought as the population is sensitive to variations in water hole depth and exposure of juveniles to predators. Events that alter key habitats and expose turtles to fish predators across the river should, accordingly, be evaluated further so they can be accounted for when managing the river.
New World Coral Snakes (genus Micrurus) occur from North to South America in a wide range of climates and habitats. Using both original and published data, we show that reproductive patterns diverge in the two phylogenetic lineages of Micrurus within the subtropical regions. Species with black rings arranged in triads are characterized by males larger than or equal in size to females, male combat behavior, and a broader season of vitellogenesis and oviposition. In these species, mating in autumn is synchronous with both spermatogenesis and vitellogenesis. Thus, females need to store sperm until ovulation in spring. In species with black rings arranged in monads, females are generally larger than males, there is no male–male combat, and seasonal vitellogenesis occurs in spring synchronous with mating. Egg laying occurs from late spring to summer, and hatchlings emerge from late summer to autumn. Spermatogenesis peaks during autumn, and males store sperm in the deferent duct over winter, until the mating season. Despite these phylogenetic trends, climatic influence on the extension of reproductive cycles was evident, with equatorial species exhibiting more continuous cycles and species from cold areas exhibiting more seasonal cycles. These two disparate reproductive strategies may be considered another differential trait between these two clades of Micrurus showing the high divergence between them.
The ecology of the genus Thamnodynastes has received little study, and problems with its taxonomy have generated imprecise and incorrect data. We analyzed the reproductive biology, sexual dimorphism, feeding ecology, habitat use, and seasonal activity of Thamnodynastes hypoconia in its subtropical–temperate area of distribution. We discuss its main ecological traits in light of the competition and predation, and the deep-history hypotheses. Males and females attained sexual maturity at different body sizes, with females achieving the largest sizes. In this species, the males and females had no difference in the body size, and males had more ventral scales than did the females. The females' reproductive cycle was seasonal and not annual, with parturition occurring in summer, whereas the cycle of the males was continuous. Thamnodynastes hypoconia feeds mainly on amphibians (97%) and occasionally on lizards (3%). As in other Thamnodynastes snakes, hylid frogs were the most common type of prey consumed (34%). Thamnodynastes hypoconia is primarily a twilight–nocturnal species that inhabits wetlands (large rivers and their floodplains), where its prey is abundant. Its activity is seasonal, with a high number of individuals encountered during the warm months. The similarity between the natural history traits of T. hypoconia (anurophagy, seasonal reproductive cycle, aquatic and nocturnal habits) and other species of the genus suggests there is phylogenetic conservatism, mainly of its ecomorphological traits, which is a pattern commonly reported for Dipsadidae snakes.
We describe a new species of Helicops from the southern Amazon Basin in the state of Mato Grosso, Brazil. It differs from all congeners by having dorsal scales in 21/21/19 rows in males and 23/21/19 rows in females, subcaudal keels, a banded dorsal color pattern, and 14–19 ventral blotches. Besides presenting information on the lepidosis and morphometric variation, we also describe the hemipenis and discuss the known distribution of the new species.
The Black Caiman (Melanosuchus niger) experienced a dramatic population decline in the mid-20th century, becoming extinct or locally rare over most of its range due to habitat destruction and the commercial value of its hide. As the success and re-establishment of the species is now dependent on conservation efforts throughout the Amazon basin, Black Caimans require continuous monitoring despite extensive current legal protection. Although such efforts have mitigated the threat of human harvesting, a key issue facing the species today is ecological competition from sympatric Spectacled Caimans (Caiman crocodilus). In this study, we investigated this inferred competition by detailing the dietary overlap between Black Caimans and Spectacled Caimans in the Pacaya Samiria National Reserve in 2009. Using an adaptation of the hose-Heimlich technique, we collected and then compared the stomach contents of several individuals of each species. We found that although the proportions of prey items in their stomach contents varied seasonally, the dietary overlap between the two species remained high, suggesting intense competition for food resources. In addition to seasonal changes, the diet composition of Black Caimans also shifted ontogenetically. Young Black Caimans primarily ate insects and crustaceans, whereas larger individuals mostly preyed on fish, reducing intraspecific competition between crocodilian adults and young. Our findings suggest that Spectacled Caimans will continue to hinder the recovery of the Black Caiman population.