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• Sceloporus variabilis is a species with males larger than females on body size. • Morphological variation in size and shape attributes in this species are unknown. • Sexual dimorphism between sexes and populations using size and shape was evaluate. • There was variation in sexual dimorphism in size, with male-biased. • There was variation in both sexes considering the shape. 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. [ABSTRACT FROM AUTHOR]

SUMMARY Using continuous seismic data from newly available broadband stations in Mexico and Central America we have obtained group and phase velocity maps of fundamental mode Rayleigh wave for the region. These new maps have been calculated for periods between 8 and 60 s from cross-correlations of seismic ambient noise between 100 broadband stations, and stacked for 30 months from 2006 to 2008. The tomographic inversion of the obtained dispersion measurements has been carried out on a 1°× 1° grid, resulting in maps with resolution better than 250 km in the well-sampled regions of the model. For short periods (8-16 s) dispersion maps show good correlation with surface structural features. Low-velocity anomalies correlate with sedimentary basins around the Gulf of Mexico and Colorado embayment. High-velocity anomalies at short periods correlate with mountain ranges and regions of thin, extended crust such as the Gulf of California. Both the lowest and highest group velocity anomalies at these periods reach values of up to 15 per cent. For periods between 25 and 40 s, velocity anomalies are related to variations in crustal thickness and temperature. The most prominent low velocity anomaly correlates with thick crust and high mantle temperatures associated with the Trans-Mexican Volcanic Belt and the Central American volcanic arc. The most remarkable features for longer periods (40-60 s) are the differences between high-velocity anomalies beneath the Mayan block, the Gulf of Mexico and the cratonic part of the United States and low-velocity anomalies beneath the Chortis block and northern Mexico. The long wavelength features of our model agree well with previous global and continental scale studies. However, because of the increased station density of the data set used, we are able to obtain reliable dispersion maps for shorter periods, and to image smaller scale features. [ABSTRACT FROM AUTHOR]