An updated list of the Mexican herpetofauna: with a summary of historical and contemporary studies.

The growth in our knowledge of the diversity of the herpetofauna of Mexico has occurred over the period of approximately 445 years from the work of Francisco Hernández to that of a broad multinational array of present-day herpetologists. The work of this huge group of people has established Mexico as one of the most significant centers of herpetofaunal biodiversity in the world. This status is the result of a complex orography, in addition to diverse habitats and environments and the biogeographic history of Mexico. The current herpetofauna consists of 1,421 native and introduced species, allocated to 220 genera, and 61 families. This figure is comprised of 1,405 native species and 16 non-native species (as of April 2023). The non-native species include two anurans, 13 squamates, and one turtle. The level of endemism is very high, presently lying at 63%, with this level expected to increase with time. Species richness varies among the 32 federal entities in the country, from a low of 50 in Tlaxcala to a high of 492 in Oaxaca. Amphibian species richness by state-level can be envisioned as comprising three levels of low, medium, and high, with the lowest levels occurring in the Peninsula of Baja California, a group of seven states in north-central and central Mexico, and a group of three states in the Yucatan Peninsula, with the highest levels occupying the southern states of Guerrero, Puebla, Veracruz, Oaxaca, and Chiapas, and the medium level in the remaining states of the country. Reptile species richness also can be allocated to three categories, with the lowest level occupying Baja California Sur, a group of central states, and the states of the Yucatan Peninsula, and the highest level found in a cluster of the states of Veracruz, Guerrero, Oaxaca, and Chiapas. Knowledge of the Mexican herpetofauna will continue to grow with additional studies on systematics, conservation, and the construction of checklists at various levels.

Does size matter? An analysis of the niche width and vulnerability to climate change of fourteen species of the genus Crotalus from North America.

The niche comprises the set of abiotic and biotic environmental conditions in which a species can live. Consequently, those species that present broader niches are expected to be more tolerant to changes in climatic variations than those species that present reduced niches. In this study, we estimate the amplitude of the climatic niche of fourteen species of rattlesnakes of the genus Crotalus to evaluate whether those species that present broader niches are less susceptible to the loss of climatically suitable zones due to the projected climate change for the time period 2021-2040. Our results suggest that for the species under study, the breadth of the niche is not a factor that determines their vulnerability to climatic variations. However, 71.4% of the species will experience increasingly inadequate habitat conditions, mainly due to the increase in temperature and the contribution that this variable has in the creation of climatically suitable zones for most of these species.

Love bites: male frogs (Plectrohyla, Hylidae) use teeth scratching to deliver sodefrin precursor-like factors to females during amplexus.

BACKGROUND: Efficient transfer of chemical signals is important for successful mating in many animal species. Multiple evolutionary lineages of animals evolved direct sex pheromone transmission during traumatic mating-the wounding of the partner with specialized devices-which helps to avoid signal loss to the environment. Although such direct transmission modes of so-called allohormone pheromones are well-documented in invertebrates, they are considered rare in vertebrates. Males of several species of the frog genus Plectrohyla (Hylidae, Anura) have elongated teeth and develop swollen lips during the breeding season. Here we investigated the possibility that these structures are used to scratch the females' skin and apply allohormone pheromones during traumatic mating in several Plectrohyla species. RESULTS: Our behavioural observations revealed that males press their upper jaw onto the females' dorsum during amplexus, leaving small skin scratches with their teeth. Histological examinations of the males' lips identified specialized mucus glands, resembling known amphibian pheromone glands. Whole-transcriptome sequencing of these breeding glands showed high expression of sodefrin precursor-like factor (SPF) proteins, which are known to have a pheromone function in multiple amphibian species. CONCLUSIONS: Our study suggests SPF delivery via traumatic mating in several anuran species: the males have specialized breeding glands in the lips for production and secretion and use their elongated teeth as wounding devices for application. We hypothesize that these SPF proteins end up in the females' circulatory system, where understanding their exact function will require further molecular, physiological and behavioural testing.

Sexual dimorphism in size and shape among populations of the lizard Sceloporus variabilis (Squamata: Phrynosomatidae).

Sexual dimorphism in lizards is determined by ecological and environmental factors. Broadly distributed species may show variation in patterns of sexual dimorphism toward either sex, as well as exhibiting variation in morphological dimensions. In the present study, sexual dimorphism in size and shape attributes was evaluated in three populations of the lizard Sceloporus variabilis from different environments in Mexico. We evaluated the size attributes of 10 morphological variables: snout-vent length (SVL), tibia length (TL), femur length (FeL), forearm length (FoL), interaxial distance (ID), head length (HL), head width (HW), head height (HH), jaw length (JL), and jaw width (JW). We also evaluated the attributes of shape (relative dimensions of the 10 morphological variables). In the size attribute, sexual dimorphism was found, with males being larger than females. In the case of shape, sexual dimorphism was found, with the females being larger in relative dimensions of ID and JW. Also, the males showed larger relative dimensions in TL, FeL and FoL. Differences were found between populations in the dimension of the variables analyzed in each sex. The pattern in size can be explained by sexual selection, where the males of each population maintain larger dimensions to compete for territory and access to females. In shape, females can be favored if they have larger relative ID and JW, as it promotes maintenance of clutch sizes, and use of microhabitats and different consumption of prey types than males. In the case of males, relative dimensions of TL, FeL and FoL may be functioning as important traits for escape from predators. The present study shows the importance of incorporating size and shape variables into analyses of sexual dimorphism among populations of a single species with a wide distribution. These types of studies help to identify the causes that promote sexual dimorphism, as well as the degree of difference among populations that inhabit different environments.

An updated checklist of the herpetofauna of Querétaro, Mexico: species richness, diversity, and conservation status.

Mexico contains a large number of amphibian and reptile species, and the states in the southeastern part of the country are the richest and most diverse. Although the study of species richness within Mexico's individual states has been increasing over the last two decades, herpetofaunal species lists for several states in the central region are incomplete. Herein, we provide a list of the herpetofauna of the state of Querétaro, a state that remains relatively unexplored. We also indicate the conservation status of the component species in the state, based on the national and international categorizations, as well as their Environmental Vulnerability Scores (EVS). Based on a review of literature and specimens in scientific collections, our results show that the herpetofauna of Querétaro currently is composed of 138 species, of which 34 are amphibians (27 anurans and seven caudates) and 104 are reptiles (three turtles, 34 lizards, and 67 snakes). The number of Mexican endemic species occurring in the state consists of 19 amphibians and 50 reptiles, representing 55.9% and 48.1%, respectively, of the total numbers in these groups. A total of 61 species (13 species of amphibians and 48 of reptiles) are listed in NOM-059-SEMARNAT-2010, within the categories of Special Protection (Pr) and Threatened (A). According to the International Union for Conservation of Nature (IUCN 2019), 34 species of amphibians (100% of species) and 87 species of reptiles (83.65% of a total of 104) have been placed within a risk category, i.e., except for the DD and NE categories. The EVS results show that nine species of amphibians have high environmental vulnerability, 11 species medium vulnerability, and 14 low vulnerability, whereas among the reptiles, 22 species have high vulnerability, 43 medium vulnerability, and 37 species low vulnerability. The herpetofauna of Querétaro illustrates a high level of species richness, which is typical of central Mexico, as well as diverse groupings associated with the arid, temperate, and tropical environments found in the state. These types of studies are necessary for increasing our knowledge of the herpetofauna in the various states of Mexico, as well as for evaluating the conservation status and implementing management plans for species in both herpetofaunal groups.

Ecology of the growth of Anolis nebulosus (Squamata: Dactyloidae) in a seasonal tropical environment in the Chamela region, Jalisco, Mexico.

Juvenile growth rates are thought to be restricted by available food resources. In animals that grow throughout the year, such as tropical lizards, growth is therefore predicted to be faster during the rainy season. We test this prediction using a population of Anolis nebulosusby describing the growth trajectories of both sexes using nonlinear regression models, and we then correlate the growth rates of individuals with food available in the environment, precipitation, and temperature. The Von Bertalanffy model fits the growth rates of the females better, while the logistic-by-length model fits the males better. According to both models, the males grew faster than females, reaching slightly smaller sizes at adulthood. Males reached sexual maturity when 35 mm long, at an age of seven months, and females matured at 37 mm (SVL), taking nine months to reach this size. In 1989, juvenile males and females grew more in both seasons (rainy and dry) than adults; for 1990, there were no differences by season or between age classes. These results are interesting since in the 1989 and 1990 rainy seasons, practically the same orders of prey and the greatest abundance of prey available in the environment were registered. A possible explanation could be that predation was more intense in 1990 than in 1989. There is little evidence that food, temperature, and humidity affect growth rates of A. nebulosus, refuting our predictions. This is mainly due to the low variation in growth observed in 1990. Therefore we think that the growth of this species reflects a complex combination of ecological and genetic factors.

Amphibian life history in a temperate environment of the Mexican Plateau: dimorphism, phenology and trophic ecology of a hylid frog, Hyla eximia (=Dryophytes eximius).

The study of demographic and life history aspects of an organism provides valuable information for its conservation. Here, we analyze the phenology of the Mountain Treefrog Hyla eximia (= Dryophytes eximius) in a temperate environment of the Mexican Plateau. Females were larger in snout-vent length and body mass than males. The peak period of activity occurred in the rainy season (May-September), with amplexus and egg deposition occurring between June and July, and larval development from July to August. A logistic model best explained observed male growth patterns, while the Von Bertalanffy model better described female growth. Notably, males grew faster than females, although females reached a larger overall body size. The diet of this species is made up of 10 prey categories. The index of diet importance indicated that males feed mainly on Coleoptera and Diptera, while females feed on Coleoptera, Diptera, Hemiptera, and Aranea. Both females and males showed a significant abundance of plant material in their stomachs, suggesting that H. eximia might exhibit highly specialized feeding behavior. Reproduction was seasonal, and both female and male reproductive cycles are synchronized with the rainy season. These natural history characteristics provide information to better understand their responses to environmental conditions.

Reproductive cycles and reproductive strategies among populations of the Rose-bellied Lizard Sceloporus variabilis (Squamata: Phrynosomatidae) from central Mexico.

Species with wide distribution, generally show variations in life history characteristics, which can be attributed to environmental causes. In this study, we analyzed the reproductive cycle and reproductive characteristics from three populations (Atlapexco, San Pablo Tetlapayac, and Santa Catarina) of the lizard Sceloporus variabilis from central Mexico. The specific goal of this study was to evaluate life history characteristics such as reproductive period extent, SVL (snout-vent length) at sexual maturity, clutch size, egg mass and volume, and RCM (relative clutch mass). The San Pablo Tetlapayac population showed a larger clutch size, RCM, egg mass, and a smaller SVL, body mass and reproductive period (January-September), as well as egg volume than the Atlapexco and Santa Catarina populations. Reproductive cycle and reproductive characteristics were more similar between the Atlapexco and Santa Catarina populations. Differences found in the population of San Pablo Tetlapayac with respect to the Atlapexco and Santa Catarina populations could be attributed to environmental variations where lizard populations occur. Differences in the reproductive period and reproductive characteristics in each population could be the result of both historical (phylogenetic; e.g., reproductive mode) and nonhistorical (environmental; e.g., temperature, food availability) causes. This study showed that populations of the same species are under different selection pressures, and these affect the reproductive characteristics of populations. Our results also indicate that long-term and targeted studies on predation, use and selection of food, are needed to determine the causes of these variations in populations of S. variabilis.