Abstract The sewage snail Physa acuta, native to North America, is an effective invasive species around the world. In Chile, it was first reported in 2014 in the north central area of the country. So far, the species has not been recorded in southern Chile. Sampling performed in 2015 in three localities from Llanquihue Lake, Chilean Patagonia, only provided native freshwater snails. However, new collections performed in February 2018 in the same three sites were successful for physid specimens suggesting a biological invasion entailing a large southward range expansion of these snails. Here we performed morphological, microstructural and phylogenetic analyses to investigate whether the new samples belong to Physa acuta. The shell morphology, male copulatory complex and radula microstructure of the new material agree with those of the sewage snail. The molecular phylogenetic analyses using the cytochrome c oxidase subunit 1 (COI) gene confirmed morphological identification. We suggest to take prompt measures to prevent the expansion of Physa acuta in Llanquihue Lake or nearby aquatic ecosystems.

Behavioral and physiological mechanisms of thermoregulation in ectotherms are conditioned by thermal constraints. These mechanisms may be even more restrictive when environmental conditions are unfavorable for individuals, especially when sexual dimorphism segregates the sexes spatially. In order to understand behavioral and physiological regulation mechanisms, we investigated the thermal biology of Phymaturus palluma (Molina, 1782), a sexually size dimorphic, high-mountain lizard that inhabits extreme climatic conditions. P. palluma showed a bimodal activity pattern, a major peak in the morning (11:00-13:30h) and in the afternoon (15:30-18:00 h). The lizards were more active when substrate temperatures were between 25 and 28º C. The highest abundance was found around 27º C (between 11:00-12:30). Females showed greater activity than males in the early morning. Sub-adults and juveniles did not show differences in their activity pattern. There was a positive relationship between body temperature and air and substrate temperatures, suggesting typically thigmothermal regulation.

The interspecific variation of heating rates in Liolaemus lizards, suggests an adaptive value of this physiological thermoregulatory mechanism, which would allow lizards to cope with the environmental thermal restrictions, imposed to behavioral thermoregulation. This trend has barely been tested at intraspecific level, and here we explore if intraspecific variation in heating rates occurs in Liolaemus tenuis, a relative widely distributed species from central Chile. We test the hypothesis that heating rates are related to the thermal environmental conditions at which populations are exposed, by comparing the heating rates of three populations (from a latitudinal range), which inhabit under different thermal conditions. Additionally, we explore if the intrinsic factor, sex, also modulates heating rates. There was a significant intraspecific variation in heating rates, at population and gender level. These rates however, showed only a partial relationship with the environmental thermal conditions. We found that the northern population, inhabiting at higher temperature, heated slower, which might reduce the risk of overheating. On the other hand, independent of the population, females heated slower than males. The meaning of this sexual variation is unclear, but may be consequence of the significant differences in genders' social behavior. Because males defend a territory with a harem, by heating faster, they can allocate extra time in behaviors associated to the defense and maintenance of the territory.

La variación interespecífica en las tasas de calentamiento de Liolaemus pareciera ser un mecanismo fisiológico adaptativo que permitiría a los lagartos enfrentar restricciones térmicas ambientales impuestas a la termorregulación conductual. Esta tendencia ha sido raramente analizada a nivel intraespecífico y en este estudio exploramos si existe variación intraespecífica en las tasas de calentamiento de Liolaemus tenuis, una especie con rango de distribución relativamente amplio en Chile central. Probamos la hipótesis de que las tasas de calentamiento están relacionadas con la condición térmica ambiental, a través de comparaciones de las tasas de calentamiento de tres poblaciones (a lo largo de un rango latitudinal), que habitan en ambientes térmicos diferentes. Además, exploramos si el factor intrínseco, sexo, modula estas tasas de calentamiento. Las tasas de calentamiento tienen una variación intraespecífica significativa a nivel poblacional y sexual. Sin embargo, estas tasas están solo parcialmente relacionadas a las condiciones ambientales a la que están sometidas las poblaciones. La población norteña, que habita a más altas temperaturas, se calienta más lento, lo que podría reducir el riesgo de sobrecalentamiento. Por otra parte, independiente de la población, las hembras se calientan más lento que los machos. El significado de esta variación sexual no es claro, pero podría ser consecuencia de las significativas diferencias en las conductas sociales de ambos sexos. Debido a que los machos defienden un territorio con un harén, un calentamiento más rápido les permitiría asignar mayor tiempo a las conductas asociadas a la defensa y mantención del territorio.

We studied sexual and geographic variation of color patterns in the lizard Liolaemus tenuis. We counted the number of scales with different colors in two body regions, in individuals of both sexes, from three groups of populations along a latitudinal range. Color patterns showed sexual and geographic variations; females and the northern group were the darkest. The selective pressures of these color pattern variations are unclear. However, considering that L. tenuis males are territorial and polygamous, we postulate that sexual variation in color would be consequence of sexual selection involving female choice and male-male interactions (e.g. agonistic displays among males). Geographic variation may be determined by predation pressure, as there is a tendency to a color matching with the predominant color of the environment (i.e. predominance of dark colors towards scrublands).

Se estudió la variación sexual y geográfica de los patrones de coloración en Liolaemus tenuis. Se contó el número de escamas con diferentes colores en dos regiones del cuerpo, en individuos de ambos sexos y provenientes de tres grupos de poblaciones a lo largo de un gradiente latitudinal. Los patrones de coloración mostraron variaciones sexuales y geográficas; las hembras y el grupo más nortino fueron más oscuros. Las presiones selectivas que determinan estas variaciones de los patrones de coloración no son claras. Sin embargo, considerando que los machos de L. tenuis son territoriales y polígamos, se postula que la variación sexual del color sería una consecuencia de la selección sexual que involucra elección de machos por parte de las hembras y las interacciones macho-macho (e.g. despliegues agonísticos entre machos). La variación geográfica estaría determinada por presiones de depredación, dada la tendencia a la presencia de coloraciones similares a las predominantes en el ambiente (i.e. predominio de colores oscuros hacia las zonas de matorral).

We studied the cranial osteology of Microlophus atacamensis and Microlophus quadrivittatus in six coastal localities from Chile and Perú. Eleven morphometric measurements and count of some structures of the skull are considered. The results indicate that there is no osteological differences that allow to distinguish between both species. It is postulated that the absence of osteology diagnoses characters between both species, is due to a process of recent speciation that has not been able to incorporate osteological morphologic changes

Se estudió la osteología craneana de Microlophus atacamensis (<A HREF="#Donoso-Barros">Donoso-Barros 1966</A>) y Microlophus quadrivittatus (Tschudi 1845) en seis localidades costeras de Chile y Perú. Se consideraron once medidas morfométricas y conteo de algunas estructuras del cráneo. Los resultados indican que ambas especies no muestran diferencias distinguibles desde el punto de vista osteológico. Se propone que la ausencia de caracteres diagnósticos osteológicos entre ambas especies se debe a un reciente proceso de especiación que no ha incorporado cambios morfológicos en su osteología