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Plethodontids are organisms highly linked to variations in temperature and moisture in the environment. The major determinant of their body temperature is the interaction between microhabitat preferences and time of day. However, there are proposed differences in moisture and temperature preferences among age classes. This study examines how microhabitat exposure and time of day on the abundance, environmental and microenvironmental moisture and temperature, body temperature, and age demographics of Pseudoeurycea leprosa interact. Hatchlings appeared to be more abundant during the day, and their body temperature varied by microhabitat and time of day, the microenvironmental moisture of the sites that individual used were affected by the interaction between these variables. These results suggest segregation between age classes. Juveniles and adults may benefit by exploiting exposed microhabitats because their body temperature remains stable. These findings highlight the importance of understanding the responses of plethodontids to changes in their environment. [ABSTRACT FROM AUTHOR]

Populations and chromosomal races of a species often show variation in life-history characteristics due to phylogeny and environmental factors. We analysed variation in snout–vent length (SVL) and reproductive variables, such as minimum SVL at sexual maturity, litter size and embryo volume in females of the Sceloporus grammicus lizard complex, which includes seven chromosomal races as well as hybrid zones among different combinations of races (F5, F5 + 6, potential but unverified F5 + 6, F6, FM1, FM2, FM2 × F5 hybrid zone, FM3, LS and unverified SGG). The SGG, F5 and LS females were larger than F6 and FM3 females. Females with non-vitellogenic follicles and vitellogenic follicles were smaller than females with embryos. The SVL of females containing embryos varied among chromosomal races, the largest being the same as indicated above, but the smallest was the FM2 × F5 hybrid zone. Litter size was similar among chromosomal races (5.8 embryos), while embryo volumes varied among them. Two patterns of reproductive activity were found: seasonal and continuous reproduction. Our results showed the influence of environmental factors of each locality, which supports the ecological hypothesis. The use of chromosomal races did not reveal a significant phylogenetic effect, because allozyme and molecular data show only small pairwise genetic distances among the S. grammicus populations on the Mexican Plateau. [ABSTRACT FROM AUTHOR]

The body size and reproductive characteristics in populations of the same species is influenced by environmental and ecological factors. In this study, we analysed the relationship of environmental factors, morphological characters (body size and mass) and reproductive traits (clutch size) of females from 13 populations of Sceloporus variabilis. Results showed variation in snout‒vent length (SVL), body mass and clutch size among populations. An ANCOVA between SVL and clutch size showed an increase of the latter in females from Alvarado and Valle Nacional; ANCOVA between body mass and SVL revealed an increase in body mass in most populations. A canonical correlation analysis showed a positive relationship between SVL, body mass, and clutch size with elevation and precipitation, but not with temperature. Future studies should assess the effect of seasonality and food resource availability on reproductive investment among populations of S. variabilis to determine whether these characteristics are a function of differences in key ecological factors (e.g. availability of resources and seasonality) associated with each population, and determine the causes of geographic variation in morphological and life history characteristics among populations. [ABSTRACT FROM AUTHOR]

In this study, sexual dimorphism, reproductive cycles, litter size and offspring size of a population of the little‐known species Sceloporus palaciosi in central Mexico were analysed. Significant male‐biased sexual size dimorphism was recorded in snout–vent length (SVL), head length, head width, forearm length and tibia length. Both sexes showed asynchronous reproductive cycles, and males reached sexual maturity at a smaller SVL (33 mm) than females (37 mm). Testes volumes were small from January to February, testicular recrudescence began from March to June, and decreased in July, but increased again in August and September, followed by a second decrease from October to December. In females, vitellogenesis began from May until ovulation in December. Embryonic development extended from November to March, and a small number of females carried embryos through July. Mean litter size was 4.0 and was positively correlated with female SVL. The length of the reproductive period in S. palaciosi recorded in this study is longer than that recorded for other populations in other parts of this species range. Further studies are needed to clarify reproductive cycles in the other isolated populations of S. palaciosi, and then extended to other species and chromosome races in the Sceloporus grammicus complex. [ABSTRACT FROM AUTHOR]

Local and geographic variation in several life history characteristics (body size at sexual maturity, clutch size, clutch frequency, egg volume, offspring size) were analysed in the arboreal lizard Urosaurus bicarinatus in three populations (Chamela, Jalisco; Jojutla, Morelos; and Paso del Chivo, Michoacan) from two different environments (tropical dry forest and thorn bush) in Mexico. Variations in these life history traits were found to exist between populations. Adult females from Chamela exhibited smaller snout--vent length (SVL) than females from Jojutla and Paso del Chivo. A similar pattern was found in others reproductive characteristics, including clutch size, relative clutch mass, egg volume, and hatchling SVL. These differences could be interpreted in terms of trade-offs, where some populations or species under conditions of low resource availability and high mortality tend to expend higher costs on reproduction; such could be the case in the population of Chamela. However, more studies are needed in many species with a broad geographic distribution to better understand the effects of the environment and genetics on variation in life histories. [ABSTRACT FROM AUTHOR]

The genus Crotalus is well represented in all biogeographic provinces including most major vegetation communities and climatic zones described for Mexico. For this reason, we use the assumptions of panbiogeography with the objective to establish a biogeographic framework for the 26 species of rattlesnakes native to Mexico. On the basis of 1472 records, 26 individual tracks derived from the distribution of each species resulted in two generalised tracks. The first is located in the Peninsula of Baja California, in the biogeographic provinces of California and Baja California, and is identified by three species (C. enyo, C. mitchellii and C. ruber). The second generalised track is located on the eastern portion of the Transmexican Volcanic Belt, the Balsas Basin, and Sierra Madre del Sur, supported by C. ravus and C. intermedius. An analysis of partition of variance found that vegetation explains the most variation in the distribution of species. Very similar results were obtained by analysis of ancestral reconstruction for biogeographic provinces, vegetation types and elevation. Our results are consistent with different climatic events during the Pleistocene, and tectonic events such as the lifting of the Sierra Madre Occidental and Sierra Madre Oriental. In addition, our results showed similarities with historical distributions of birds, mammals and beetles. Further studies of the distribution and phylogeography of other groups of reptiles with significant information gaps in their historical and current distribution are needed to shed further light on the biogeography and diversity of reptiles of Mexico. [ABSTRACT FROM AUTHOR]