Alejandra Panzera

The complex orogenic history and structure of Southern South America, coupled with Pleistocene glacial cycles, have generated paleoclimatic and environmental changes that influenced the spatial distribution and genetic composition of natural populations. Despite the increased number of phylogeographic studies in this region and given the frequent idiosyncratic phylogeographic patterns, there is still the need to focus research especially on species that are currently distributed within a wide range of bioclimatic regimes, and that historically have been subject to contrasting scenarios. Liolaemus tenuis is a widely distributed lizard species inhabiting latitudinally in almost 1000 km through central and southern Chile. Here we describe the geographical patterns of genetic variation and lineage diversification within L. tenuis, and their association with geography and Pleistocene glaciations, using sequences from one mitochondrial and two nuclear genes, and five microsatellite loci, and covering most of the species distributional range. Our results revealed a high diversity both within and among populations, as well as two phylogeographic breaks, which are consistent with two of the larger rivers of central Chile, the Maipo and Biobío Rivers. Liolaemus tenuis is characterized by several allopatric lineages, especially in its north and central range, which suggest a history of multiple vicariance processes. Conversely, populations found in the southern range, south of the Biobío River, show signatures of recent decreases in effective population sizes, coupled with recent range expansions and secondary contact. Niche “envelope” data are consistent with patterns of genetic variation; both suggest a history of discontinuous areas of relatively stable populations throughout all of the distribution of L. tenuis. These data are also consistent with higher probabilities of habitat suitability north of the Maipo River (ca. 33°S), in both coastal areas and the “Intermediate Depression” between 34° and 37°S, as well as in the southern Coastal Cordillera between the Biobío and Araucanía regions. Interestingly, both molecular and niche envelope modeling data suggest that some populations may have persisted in fragmented refugia in Andean valleys, within the limits of the ice sheet. Finally, our results suggest that several populations of L. tenuis colonized glaciated regions from refugial areas in lowlands and coastal regions, and in the southern distribution, historic migration events would have occurred from refugial areas within the limits of the ice sheet.

The pattern of the testicular cycle and spermatogenic activity of the Neotropical yellow-striped snake Lygophis anomalus in Uru-guay was investigated. We gathered data on testicular size, seminiferous tubules, and histological samples of preserved specimens. Testis volume and seminiferous tubule diameter did not differ significantly over the year, and individuals with sperm cells were found all year round. Nevertheless, histological observations show individuals in different stages of spermatogenetic cycle within a single month sample. Our results show that, despite their continuous sperm production, males of L. anomalus populations in Uruguay exhibit a seemingly seasonal cycle, as reflected by changes in testicular volume. Reproductive pattern, even if related to evolutionary lineage, is possibly regulated by environmental factors such as low winter temperatures.

The pattern of the testicular cycle and spermatogenic activity of the Neotropical yellow-striped snake Lygophis anomalus in Uru-guay was investigated. We gathered data on testicular size, seminiferous tubules, and histological samples of preserved specimens. Testis volume and seminiferous tubule diameter did not differ significantly over the year, and individuals with sperm cells were found all year round. Nevertheless, histological observations show individuals in different stages of spermatogenetic cycle within a single month sample. Our results show that, despite their continuous sperm production, males of L. anomalus populations in Uruguay exhibit a seemingly seasonal cycle, as reflected by changes in testicular volume. Reproductive pattern, even if related to evolutionary lineage, is possibly regulated by environmental factors such as low winter temperatures.

Adult males of Eupalaestrus weijenberghi (Thorell 1894) live only for few months, while females
live many years and continue molting and growing. Hence, there is a strong female-biased operational
sex-ratio. While males move massively during the brief mating season, females are sedentary and
remain inside their burrows, which are sometimes very close to each other. We tested if males are
able to select females according to their body size and if selectivity of both sexes varies along the
mating season. We exposed 5 males to 5 pairs of females of different sizes that occupied a burrow in
each of two joined terraria. We performed two series of experiments: one at the beginning (March)
and other at the end (May) of the mating season. Threesome combinations varied without repetitions,
totalizing 25 trials on each series. We did not find differences in male behaviors: initial orientation,
body vibration, palpal drumming and mating attempts regarding female size. We did not find
differences in female behaviors as call or rejection. Courtship intensity was lower in May. This
decrease could reflect male decadence and/or lower female receptivity. Unexpectedly, females
preferred to lose their annual reproductive chance than mate with a poor quality male.