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The need for long-term demographic studies on apparently healthy amphibian populations led us to undertake an intensive examination of a population of Spotted Salamanders (Ambystoma maculatum) at a small, temporary pond in Ohio. From 2005 to 2014, we captured adults and juveniles at the pond edge, individually marked a subset of adults, and examined patterns in breeding population size, sex ratios, recruitment, differences in body size over time, and survival and recapture rates. We found that this breeding population size varied 2.65-fold across 10 yr, with an overall negative trend driven by a decline in adult males, despite the fact that adult annual survival was not dependent on sex, and that males were more likely to be recaptured annually than were females. We also found that recruitment rates were low and never reached replacement values. Body sizes varied across years for adults as well as for emerging juveniles, and females lost a larger fraction of their mass in the pond than males, especially as time in the pond increased. Some demographic variables were consistent with previous shorter term studies. We found unusually low recruitment and annual recapture rates, however, in addition to a decline in males over time, which might reflect an expansion of our understanding of what is typical for this species. It might also indicate that our population was in the early stages of decline, potentially affected by changes in hydroperiod and increases in infectious disease mortality.
Amphibian diversity in Neotropical mountains habitats is at risk, particularly those species associated with stream habitats at altitudes >500 m above sea level (a.s.l.). This pertains especially to the amphibian diversity of Mexico, where the number of species is high on the central and southwestern highlands. In the present study, we predicted the potential distribution of Ambystoma ordinarium using a Geographic Information System modeling approach. We used survey data from 2013 to 2015 and historical data reported in databases and literature, and employed environmental variables from the WorldClim–Global Climate Data Project. Our results indicate that a single factor, Mean Diurnal Range, contributed most to the model, followed by other factors (Minimum Temperature of the Coldest Month and Precipitation of the Driest Month). The conservative predicted distribution was 5256 km2, especially in areas have dynamic aquatic ecosystems (e.g., small streams). The highest probability of occurrence of the species at locations of 1900–2900 m a.s.l., with 13.7–16.3°C diurnal terrestrial air temperatures, and annual precipitation of 829–1454 mm. In these areas, native forest vegetation has decreased by almost 250 km2, and native grassland by 280 km2. Agricultural activities, human settlements, and secondary succession vegetation increased by 160, 120, and 330 km2, respectively. We infer that A. ordinarium is susceptible to changes in habitat, with most of the constraint on the distribution of this species arising from deforestation, increased urbanization and agricultural activities. Based on our model, and a recent genetic study, we suggest that the population of this species from lower elevations could be considered a different taxon. Consequently, the relative species distribution boundaries should be redefined, and appropriate monitoring programs redesigned to support conservation of the Michoacan stream salamander.
In the majority of anuran species, acoustic signals are the dominant mode of inter- and intrasexual communication. Male calls are always accompanied by the movement of a more or less conspicuous vocal sac—a potential visual cue. Reed frogs possess a striking vocal sac with a colorful patch of gland tissue clearly visible once the vocal sac is inflated during acoustic signaling. To investigate the visual signal function of vocal sac and gular gland, we presented male Spotted Reed Frogs (Hyperolius puncticulatus) with unimodal and multimodal signal playbacks of conspecific rivals in their natural habitat and recorded their behavioral responses. We found no difference in receiver response to unimodal advertisement call stimuli and to multimodal stimulus presentations of calls combined with visual signals of an artificial vocal sac with or without a gular patch, moving synchronously or asynchronously with the call playback. The inflations of a vocal sac with a colorful gular patch did not alter receiver response and neither increase nor decrease signal salience during male–male communication. Interestingly, males frequently displayed a novel hind and front foot-tapping behavior in response to all playbacks. Comparison of male responses to advertisement and aggressive call playbacks showed that Spotted Reed Frogs approached the sound source less during aggressive call presentations. Tapping behavior was not influenced by either call playback. We suggest that the gestural tapping behavior might act as vibrational signal and discuss its potential signal function in male contests and courtship for females.
Diamond-Backed Terrapins (Malaclemys terrapin) are emydid turtles found in estuarine systems along the Gulf and Atlantic coasts of the United States between Texas and Massachusetts, and in Bermuda. Reductions in many terrapin populations have been documented throughout the species' range in association with habitat loss, overharvesting for consumption, bycatch in commercial and recreational fishing gear, and collection for the pet trade. Information on populations within Louisiana is limited, with survey efforts being performed only recently throughout the state's coastal zone. From 2012 through 2014, we sought to determine the distribution of Diamond-Backed Terrapins within the Deltaic Plain region of Louisiana, describe sex ratios and size class structure within select management basins, and establish marked populations to promote continued study of the species. Of the 27 terrapin sampling sites initially selected, 24 were chosen for further evaluation; a subset of these same locations were sampled more intensively in 2014. In all years, we utilized unbaited fyke nets. The presence of Diamond-Backed Terrapins was associated with a variety of coastal marsh vegetative communities (e.g., intermediate, brackish, and saline). Basin-specific analyses revealed variation in mean size, and sex ratios skewed toward males within all basins indicating higher female mortality rates or male-biased recruitment. These efforts confirm the presence of Diamond-Backed Terrapins across the Deltaic Plain region of the Louisiana coastline, and inform future examinations of the regional and range-wide abundance and population dynamics of the species.
Malaclemys terrapin inhabits salt marshes of the coastal United States and has been historically divided into seven subspecies. Two of the described subspecies, M. t. pileata and M. t. littoralis, occur along the western and eastern coastlines of Louisiana, respectively. To better understand potential boundaries of these two subspecies, we documented pigmentation variation of the plastron along the coast of Louisiana where the subspecies supposedly intergrade. Photographs of the plastron were taken of captured individuals and we quantified pigment with a photoprocessing software (ImageJ). We found pigmentation differences between sexes, with females having lighter plastrons than males. The plastron pigmentation of females decreased with increasing plastron length, whereas that of males varied by site but not length. Plastron pigmentation did not correlate with longitude in either sex, indicating that there is no geographical cline in this trait. We suggest that large females might be released from the predation pressure of gape-limited predators, and therefore, can stop production of melanin as they grow. However, males and smaller females maintain cryptic, dark plastrons. Little is known about the mechanisms behind melanization in freshwater turtles, but understanding the patterns of pigmentation variation in M. terrapin might be important for taxonomists and conservation managers.
Incubation temperature is one of the most studied factors driving phenotypic plasticity in oviparous reptiles and has been shown to affect a wide variety of traits including body size, shape, and performance. Thermal regimes during embryogenesis might therefore have direct consequences on fitness, potentially even shaping population trajectories. These effects are likely strongest in short-lived species where even temporary temperature-induced differences in body size or shape might have adaptive significance. We investigated the effects of incubation temperature on the body size and shape of hatchling Australian Painted Dragons (Ctenophorus pictus). Eggs incubated at low temperature required a longer incubation period, but produced hatchlings of greater body mass. However, no effect of temperature was found on the structural dimensions of hatchlings. These results might be explained by an increased absorption of water by the developing embryo during the prolonged incubation period. A greater water content might increase early-life desiccation tolerance in this short-lived lizard inhabiting arid and semiarid environments. Egg mass, however, had the strongest effect on hatchling phenotype, with larger eggs producing larger hatchlings. Furthermore, there was a seasonal effect on yolk allocation, with eggs laid earlier being larger than those laid later. Our results indicate that yolk allocation is the most important factor affecting hatchling phenotype in this species, while temperature mainly affects embryo developmental rate and likely has an indirect effect on hatchling water content.
The ability to discriminate among potential prey is foundational for predators making foraging decisions, as well as for the evolution of food preferences. Eastern Indigo Snakes (Drymarchon couperi; EIS) are federally threatened and considered dietary generalists, but qualitative evidence indicates that snakes are consumed more often than other prey types. In this study, we used a repeated-measures tongue-flick assay to investigate EIS response to prey scent experimentally, and made inferences about potential preferences. Hatchling EIS responded more strongly to scents from snakes as compared to their response to scents from mice or controls. Moreover, hatchling EIS discriminated between the scents of representative colubrid and crotaline snakes, exhibiting a stronger response to the latter. A follow-up experiment using scents from three different species of pit vipers indicated that hatchling EIS did not discriminate among scents from members of this snake subfamily. After a year in captivity in which EIS were primarily fed mice, we retested a subset of the same snakes and documented an increased response to the scent of mice, whereas responses to snake prey scents did not change. Broadly, we reveal that hatchling EIS have relatively strong responses to scents from snake prey that vary depending on the species, and these responses becomes less pronounced over time. Given that relatively strong responses typically indicate preference, there are at least two potential explanations for the increased response to mouse scent over time: Either EIS exhibit an innate ontogenetic shift in prey preference towards mice, or their prey preference is plastic and influenced by diet in captivity. Given what is known about EIS natural history, the latter explanation is most likely. Overall, our study provides detailed information regarding chemosensory prey discrimination by EIS, with important implications for their ongoing reintroduction efforts.
We describe a new species of lentic salamander of the genus Hynobius. From our examination of specimens from the Kyushu and Shikoku populations of Hynobius dunni, individuals of each population have distinct morphological and molecular traits. On this basis, we describe the Shikoku population as a new species. Morphological comparisons revealed that most individuals of H. dunni possessed distinct black spots on the dorsum, but that the new species lacks these spots. Furthermore, the mean snout–vent length was smaller for the new species than for the Kyushu population of H. dunni. Phylogenetic analyses with the use of fragments of the 16S rRNA and cytochrome b genes also distinguish the new species from individuals in the Kyushu population. The new species has been found in only seven artificial ponds, with approximately 80 clutches of eggs found each year. This endangered species might have the smallest distribution of all those in the genus Hynobius.
I review the taxonomic status of four species of Craugastor of the phenetic-based C. laticeps species group from the Cordillera Nombre de Dios (CND) and nearby mountains in north-central Honduras. These frogs were tentatively assigned to previously described species. Specimens of recently collected frogs, along with some of those previously examined, were compared with similar frogs from northwestern Honduras (in three cases) and with a population from eastern Honduras. These new morphological analyses demonstrate that two of those CND populations are best treated as new species. One population appears most closely related to C. laticeps from northwestern Honduras, but is distinguished from that species by having a smaller adult male size, a larger adult male tympanum, a distinct dark eye mask that extends posteriorly to at least level of midbody, and a dark seat patch mark. The second new species appears most similar to C. rostralis from northwestern Honduras, but reaches a larger size and has a gold upper half of the iris, a dark seat patch mark surrounded by white pigment, a more tuberculate outer tarsal segment, and a more tuberculate outer edge of the forearm. In addition to those morphological differences, both new species occur in habitats of montane mesic broadleaf forest that are separated from their apparent closest relatives by low-elevation valleys containing open, subhumid, and hotter forests types. Based on ∼40 yr of field surveys, it is apparent that C. laticeps group species are unable to tolerate those subhumid habitats. Study of the two remaining CND forms demonstrates that they are best treated as conspecific with two previously described species. A type-locality restriction is made for the closest relative of one new species that previously carried the type locality “Honduras.” A discussion of amphibian endemism in the CND is also included.
Although the recognized distribution of Japalura kumaonensis is restricted largely to western Himalaya, a single, isolated outlier population was reported in eastern Himalaya at the China-Nepal border in southeastern Tibet, China in Zhangmu, Nyalam County. Interestingly, subsequent studies have recognized another morphologically similar species, J. tricarinata, from the same locality in Tibet based on photographic evidence only. Despite these reports, no studies have examined the referred specimens for either record to confirm their taxonomic identifications with robust comparisons to congener species. Here, we examine the referred specimen of the record of J. kumaonensis from southeastern Tibet, China; recently collected specimens from the same locality in southeastern Tibet; type specimens; and topotypic specimens of both J. kumaonensis and J. tricarinata, to clarify the taxonomic identity of the focal population from southeastern Tibet, China. Our results indicate that individuals of the referred Tibetan population differ from J. kumaonensis in external morphology, but match descriptions and specimens of J. tricarinata. We conclude that the previous record of J. kumaonensis from Tibet was a misidentification of J. tricarinata, and J. kumaonensis should be recognized as occurring in western Himalaya only. To facilitate future taxonomic studies of the genus Japalura sensu lato in the Himalaya, we provide a detailed description of J. tricarinata and an updated diagnostic key to the genus from the Himalaya.