The Pampas is a biologically rich South American biome, but is poorly represented in phylogeographic studies. While the Pleistocene glacial cycles may have affected the evolutionary history of species distributed in forested biomes, little is known about their effects on the habitats that remained stable through glacial cycles. The South American Pampas have been covered by grasslands during both glacial and interglacial periods and therefore represent an interesting system to test whether the genetic structure in such environments is less pronounced. In this study, we sampled Pampean populations of Homonota uruguayensis from Southern Brazil and Uruguay to assess the tempo and mode of population divergence, using both morphological measurements and molecular markers. Our results indicate that, in spite of its narrow geographic distribution, populations of H. uruguayensis show high levels of genetic structure. We found four major well-supported mtDNA clades with strong geographic associations. Estimates of their divergence times fell between 3.16 and 1.82 million years before the present. Populations from the central portion of the species distribution, on the border between Uruguay and Brazil, have high genetic diversity and may have undergone a population expansion approximately 250,000 years before the present. The high degree of genetic structure is reflected in the analyses of morphological characters, and most individuals could be correctly assigned to their parental population based on morphology alone. Finally, we discuss the biogeographic and conservation implications of these findings.
ABSTRACT. Microhabitat use by Cnemidophorus vacariensis Feltrim & Lema, 2000 as studied between October 2006 and September 2007 in two rocky formations in the municipality of Bom Jesus. The area was searched randomly between 8:00 am and 6:00 pm and the microhabitat used by the lizards was recorded. Our observations revealed that C. vacariensis has terrestrial habits and prefers open areas. Burrows are the main microhabitat used by the species (56.38%). When in activity, 54.76% of the individuals were observed under rocks, and 38.1% on the ground where herbaceous vegetation was present. The rocks under which they constructed their burrows were on average significantly thicker during warmer seasons temperatures (x = 13,45cm) with respect to colder seasons (x = 9,85cm). The rocks selected by the adults (x = 12.94 cm) were on average significantly thicker than those selected by the juveniles (x = 9.86cm). There were no statistically significant differences between sexes with respect to rock thickness.
ABSTRACT. We investigated the following aspects of the biology of a population of Cnemidophorus vacariensis Feltrim & Lema, 2000 during the four seasons: thermal biology, relationship with the thermal environment, daily and seasonal activity, population structure and growth rate. Cnemidophorus vacariensis is restricted to rocky outcrops of the "campos de cima da serra" grasslands on the Araucaria Plateau, southern Brazil, and is currently listed as regionally and nationally threatened with extinction. Data were collected from October 2004 through September 2007 in the state of Rio Grande do Sul. Sampling was conducted randomly from 08:00 a.m. to 6:00 p.m. The capture-mark-recapture method was employed. The lizards were captured by hand, and their cloacal temperature, sex, snout-ventral length (SVL), mass, and the temperature of their microhabitat (substrate temperature and air temperature) were recorded. Individuals were then marked by toe-clipping and released at the site of capture. Body temperatures were obtained for 175 individuals, activity data for 96 individuals, and data on population structure and growth for 59 individuals. All data were obtained monthly, at different times of the day. Cnemidophorus vacariensis average body temperature was 23.84°C, ranging between 9.6 and 38.2°C. Temperatures ranged between 21 and 29°C. The correlation between external heat sources, substrate and air were positive and significant and there was a greater correlation between lizard's temperature and the temperature of the substrate (tigmothermic species). The relatively low body temperatures of individuals are associated with the climate of their environment (altitude up to 1,400 m), with large variations in temperature throughout the day and the year, and low temperatures in winter. The average body temperature observed for C. vacariensis was low when compared with that of phylogenetically related species, suggesting that the thermal biology of this species reflects adaptations to the temperate region where it lives. The monthly rates of activity of lizards were related to monthly variations in the ambient temperatures. Our data suggest that the daily and seasonal activity of C. vacariensis result from the interaction between two factors: changes in the environment temperature and the relationship between individuals and their thermal environment. The population structure of C. vacariensis varied throughout the study period, with maximum biomass in January and maximum density in February (recruitment period). The sex ratio diverged from the expected 1:1. The growth analysis showed a negative relationship between the growth rate of individuals and the SVL, revealing that young individuals grow faster than adults, a typical pattern for short-lived species. The population studied showed a seasonal and cyclical variation associated with the reproductive cycle. The life strategy of C. vacariensis seems to include adaptations to the seasonal variations in temperature, typical of its environment. KEYWORDS.Body temperature, grow...
Population dynamics of the lizard Tropidurus torquatus was studied between May 2008 and June 2009 in a rocky formation in Alegrete municipality, Rio Grande do Sul state, southern Brazil. The study was carried out using the capture, marking and recapture method, the area being randomly searched from 08:00 am to 6:00 pm. Tropidurus torquatus presented variation in population structure throughout the study period, with maximum biomass observed in October 2008 and maximum density occurring in November 2008 (reproductive season), both having a second peak in March 2009 (recruitment period). There was a significant difference between the number of juveniles and adults recorded, since adults were present throughout the study period while juveniles were present in the months after recruitment. The difference found between males and females may be related to a social territorial behavior of the males. The population of Tropidurus torquatus presented a cyclic and seasonal variation in population structure, possibly associated with the reproductive cycle of the species, with differences in the distribution of age classes and sexual proportions throughout the year.KEY-WORDS. Tropidurus, population structure, sex ratio, age classes, social behavior.
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