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A series of articles written by former presidents of the Herpetologists' League has been organized to commemorate the 75th volume of Herpetologica. In this preamble to the series, I summarize the journal's history and that of a few other periodicals published by the League. After describing some aspects that have contributed to the continued success of Herpetologica, I briefly outline the publication model that will take effect with this volume.
Over 9000 articles have been published on turtles and tortoises (excluding sea turtles) since 1950 according to the Web of Science, including over 8000 contained in a personal bibliography that we analyze in this paper. Research had a slow start from 1900 to 1950, with mostly anecdotal additions to our knowledge until the contributions of F. Cagle and A. Carr took turtle research to new levels as the cofathers of turtle ecology in the middle of the last century. Books written in 1939, 1952, and 1972 that compiled existing literature on turtles in the United States and Canada set the stage for growing interest in turtles. The first global compilation of turtle species did not become available until 1961. Publication frequency increased in the 1960s and especially the 1970s as interest in turtles grew, and a wave of turtle biologists emerged from doctoral degree programs. We briefly review the contributions of scientists who published extensively on turtle ecology in those and later decades up to the present. We also review advances in our knowledge of various topics, including the global distribution of turtle research efforts; changes in our perceptions of turtle species diversity over time; turtle community ecology; sex ratios, sex-determination, and climate change; overwintering behavior; sexual size dimorphism and sexual dichromatism; analyses of population genetics; turtles and vocalization; and the emergence of turtle conservation biology efforts. We conclude with a discussion of future opportunities and challenges for working with turtles.
Hellbenders (Cryptobranchus alleganiensis) are long-lived, fully aquatic salamanders that inhabit cool, well-oxygenated streams and rivers in the eastern United States. Although once abundant, C. alleganiensis populations have experienced major declines across the historical range. Habitat degradation, siltation, aquatic contaminants, and infectious diseases are commonly suggested as contributors to these declines. Although Tennessee provides areas of high-quality habitat for C. alleganiensis, microhabitat differences among life stages are not well documented. We evaluated microhabitat use of larval, subadult, and adult C. alleganiensis at three streams in east Tennessee by comparing sites occupied by C. alleganiensis to random sites within each stream. We used multivariate analysis to evaluate microhabitat use differences among larval, subadult, and adult C. alleganiensis. We completed habitat assessments for 60 individuals. We detected an association between C. alleganiensis presence (regardless of life stage) and the percentage of large rock, the percentage of low embedded rocks, and the number of rocks above 500 mm. Furthermore, the volume of cover rock, the number of rocks above 500 mm, the distance to bank, and the percentage of low embedded rocks, gravel, and sand were the most important microhabitat attributes to discriminate life-stage distributions. Overall, our analyses identify microhabitat attributes that are potentially important for long-term C. alleganiensis conservation and provide guidance for stream protection and restoration practices that might mitigate sedimentation and habitat degradation in impacted streams.
Phenotypic variation along environmental gradients—particularly in body size—occurs in a variety of species. Larger-bodied individuals are usually found in colder climates, as predicted by Bergmann's rule. In ectotherms, this pattern remains controversial. Among thermoconformers, smaller body sizes are expected in colder climates because these species might have relatively shorter warm-up times (advantageous in cold climates), whereas the reverse pattern can be expected in thermoregulators (heat-balance hypothesis). In amphibians, additional factors like humidity and thermal niche might also contribute to body-size variation. Following Allen's rule, there can also be a negative relationship between temperature and relative limb length. Here, we described associations among temperature, precipitation, body size, and relative limb length in Calotriton asper. We expected individuals from higher elevations (colder climates) to be smaller when compared to lowelevation conspecifics. We found an influence of temperature on body-size variation but, contrary to expectations, salamanders from colder climates were larger compared to low-elevation populations, which corroborates with the heat-balance hypothesis. In accordance with the converse water-availability hypothesis, we also demonstrated that precipitation was related to body-size variation in this species. Finally, our results supported the predictions of Allen's rule. This trend could be the result of evolutionary responses to harsh environments, driven by either local adaptation, plasticity processes, or a combination of both.
For most pond-breeding anurans, movement is fundamental for foraging, reproduction, avoidance of adverse environmental conditions, and predator avoidance and escape. Although the influence of environmental factors such as temperature and rainfall on anuran activity other than movement is well documented, the effect of these factors on anuran movement is less clear. In this study, we examined the influence of environmental factors on distances moved by 11 adult male Butter Frogs (Leptodactylus latrans) during their breeding season. We fitted movement data as the response variable and environmental factors as fixed effects in generalized linear models and performed model selection and model averaging to understand the contribution of each variable to movement. We were not able to identify any environmental factors that trigger movement in Leptodactylus latrans, but distance moved was positively related to darker phases of the moon, higher temperatures, and greater rainfall. Behavioral response to the lunar cycle is believed to be associated with predator avoidance and reproduction synchronization, whereas responses to temperature and rainfall are most associated with water balance and metabolic regulation.
Habitat disturbance is an important cause of global amphibian declines, with especially strong effects in areas of high agricultural use. Determining the influence of site characteristics on amphibian presence and success is vital to developing effective conservation strategies. We used occupancy analysis to estimate presence of four anuran species at wetlands in northern Iowa as a function of eight environmental covariates hypothesized to affect occupancy: fish and salamander abundance, invertebrate density, aquatic vegetative cover, wetland area, atrazine concentration in water, surrounding agricultural land use, and an overall wetland health score (wetland condition index [WCI]). We surveyed 27 wetlands multiple times in 2015 and 2016. Leopard Frogs (Lithobates pipiens) and American Toads (Anaxyrus americanus) were observed at 100% of the sites, Boreal Chorus Frogs (Pseudacris maculata) at 96%, and Gray Treefrogs (Hyla spp.) at 81%. Wetland site occupancy for all species in our study ranged from 0.23 (Hyla spp. tadpoles) to 0.95 (L. pipiens adults), indicating that agricultural wetlands can provide refuge or habitat for amphibians. Fish abundance, percentage of cropland cover within 500 m of the wetland, and salamander abundance were among the variables best supported by our models although their estimated effects were weak. Wetland area, atrazine concentration, vegetative cover, and WCI also influenced occupancy probability, but for only a small number of species and life stages. The direction of predicted effects varied by species and life stage. Despite only weak evidence that the environmental factors we measured influenced anuran occupancy, our results provide insights for managers seeking to understand how amphibians use landscapes modified by agriculture.
Temperature-dependent sex determination, where egg incubation temperature irreversibly determines offspring sex, is a common sex-determining mechanism in reptiles. Weather is the primary determinant of temperature in reptile nests, yet the effects of weather are mediated through the nest microhabitat selected by the mother (e.g., overstory canopy cover). One potentially important aspect of the nest microhabitat is the physical substrate used for nesting. However, the influence of substrate type on nest temperature and offspring sex determination has never been experimentally assessed in the field. We incubated eggs of Painted Turtles (Chrysemys picta) in three substrate types similar to those commonly selected for nesting within our study population. Within a single study site, we constructed pits, which we refilled with loam, sand, or gravel. Then, we created artificial nests in each substrate type, and randomly assigned eggs to a substrate treatment. Substrate type influenced nest temperature and soil moisture, and affected incubation duration, but no other phenotype measured beyond offspring sex ratios. The cooler loam yielded the most male-biased outcome. This finding illustrates the potential importance of nesting substrate as a component of nest-site choice and as a factor in modeling future nest-temperature scenarios.
Ultrastructures of chelonian eggshells show wide interspecific variation, which might, in part, reflect requirements to protect embryos in various incubation environments. Relationships between eggshell ultrastructures and incubation environments are poorly understood. Using scanning electron microscopy, we examined ultrastructures of eggshells from wild and captive Speckled Dwarf Tortoises (Chersobius signatus), including shells from hatched and undeveloped eggs. Speckled Dwarf Tortoises produce multiple single-egg clutches during a short breeding season in spring, and bury their eggs in shallow nests that experience high temperatures and low water potentials. In light of this harsh incubation environment, we expected thick calcareous layers to minimize water loss during incubation. However, wild and captive eggshells had thin calcareous layers (mean values ranging from 125.1 to 148.3 µm) that lacked the multiple crystallite layers and cuticles found in several other tortoise species. We hypothesize that thin calcareous layers in eggshells of Speckled Dwarf Tortoises might be related to the production of multiple clutches within a short breeding season, leaving little time for the calcification of each eggshell. The benefits of producing multiple clutches might outweigh the benefits of a thick eggshell. Hatched eggshells had porous crystallite cores, and the shell membrane of hatched eggshells was usually separated from the calcareous layer. These characteristics are consistent with calcium absorption from the eggshell by developing embryos, resulting in shorter crystallite heights in shells of captive hatched compared to undeveloped eggs.
Many lizards use colorful badges in displays with conspecifics during courtship and aggressive interactions. In Eastern Fence Lizards (Sceloporus undulatus), males and females reveal sexually dimorphic ventral abdominal coloration during social interactions and use these features to signal sex and perhaps other characteristics. However, the extent to which ventral badges or other chromatic features of males and females signal quality remains unresolved in this species. Additionally, adult S. undulatus exhibit temperature-dependent color change of their abdominal badges, a potential confounding variable in studies of the function of these badges. Here, we examined the relationship between spectral variables of ventral and dorsal skin color and morphometric traits linked to fitness in adult male and female S. undulatus under standardized temperature conditions. For males, ventral patch hue tended to decrease (i.e., was blue-shifted) as body size increased, whereas dorsal hue was unrelated to male size. In contrast, there was no relationship between ventral hue and body size in females, and dorsal hue increased (i.e., was red-shifted) with body size. In males, lower ultraviolet (UV) chroma and greater blue chroma of ventral abdominal badges predicted increasing body size. In females, UV chroma of the ventral abdomen was inversely related to body size and better body condition, whereas blue chroma was inversely related to body condition only. Dorsal UV chroma decreased with increasing body size in both males and females, but brightness was not a significant predictor of any morphometric trait in either sex. Overall, these results indicate that both blue and UV reflectance of ventral and dorsal abdominal skin are indices of size and thus age, and could therefore serve as indices of signaler quality in this species.
Many sexually selected traits are static throughout the breeding season. Some vary within the breeding season, however, typically in response to physiological changes. Most work attempting to understand the mechanisms underlying phenotypic changes has occurred in the laboratory, with comparatively less research examining how changes to physiology affect signal production in natural populations. Here, we report intraseasonal plasticity in abdominal and throat patch color of Prairie Lizards (Sceloporus consobrinus), and examine how changes in body size, body condition, and testosterone underlie intraseasonal variation. We found that changes in testosterone best explain why throat patches of Prairie Lizards become less blue throughout the breeding season. If females reproduce with males based on patch color, then individual changes in patch phenotypes could have important consequences if signaling morphology is asynchronous among males.
We describe two new species of Pristimantis from southwestern Colombia. The first new species inhabits the humid Pacific slopes of the Cordillera Occidental, Valle del Cauca; it is most similar to three allopatric Ecuadorian species—P. eugeniae (Lynch and Duellman 1997), P. nyctophylax (Lynch 1976), and P. subsigillatus (Boulenger 1902). It is distinguished, however, by having subarticular tubercles beneath the joint between distal phalanges, basal webbing on outer edge of toe IV, papilla at the tip of snout, and uniform cream-brown coloration on the anterior surfaces of thighs and in the groin. The second new species inhabits the high mountains of the Cordillera Central, Cauca, and it is most similar to P. boulengeri (Lynch 1981) and two Peruvian species—P. deyiLehr et al. 2013 and P. schultei (Duellman 1990). However, it differs by having subarticular tubercles beneath the joint between distal phalanges, dorsal skin with low warts, papilla at the tip of snout, and by lacking tympanic membranes, dentigerous processes of the vomer, and vocal slits.