Marcelo Fabián Bonino

Chasing the Patagonian sun: comparative thermal biology of Liolaemus lizards

The importance of the thermal environment for ectotherms and its relationship with thermal physiology and ecology is widely recognized. Several models have been proposed to explain the evolution of the thermal biology of ectotherms, but experimental studies have provided mixed support. Lizards from the Liolaemus goetschi group can be found along a wide latitudinal range across Argentina. The group is monophyletic and widely distributed, and therefore provides excellent opportunities to study the evolution of thermal biology. We studied thermal variables of 13 species of the L. goetschi group, in order to answer three questions. First, are aspects of the thermal biology of the L. goetschi group modelled by the environment or are they evolutionarily conservative? Second, have thermal characteristics of these animals co-evolved? And third, how do the patterns of co-evolution observed within the L. goetschi group compare to those in a taxonomically wider selection of species of Liolaemus? We collected data on 13 focal species and used species information of Liolaemus lizards available in the literature and additional data obtained by the authors. We tackled these questions using both conventional and phylogenetically based analyses. Our results show that lizards from the L. goetschi group and the genus Liolaemus in general vary in critical thermal minimum in relation to mean air temperature, and particularly the L. goetschi group shows that air temperature is associated with critical thermal range, as well as with body temperature. Although the effect of phylogeny cannot be ignored, our results indicate that these thermal biology aspects are modelled by cold environments of Patagonia, while other aspects (preferred body temperature and critical thermal maximum) are more conservative. We found evidence of co-evolutionary patterns between critical thermal minimum and preferred body temperature at both phylogenetic scales (the L. goetschi group and the extended sample of 68 Liolaemus species).

Running in cold weather: morphology, thermal biology, and performance in the southernmost lizard clade in the world (Liolaemus lineomaculatus section: Liolaemini: Iguania)

The integration or coadaptation of morphological, physiological, and behavioral traits is represented by whole-organism performance traits such as locomotion or bite force. Additionally, maximum sprint speed is a good indicator of whole-organism performance capacity as variation in sprinting ability can affect survival. We studied thermal biology, morphology, and locomotor performance in a clade of Liolaemus lizards that occurs in the Patagonian steppe and plateaus, a type of habitat characterized by its harsh cold climate. Liolaemus of the lineomaculatus section display a complex mixture of conservative and flexible traits. The phylogenetically informed analyses of these ten Liolaemus species show little coevolution of their thermal traits (only preferred and optimum temperatures were correlated). With regard to performance, maximum speed was positively correlated with optimum temperature. Body size and morphology influenced locomotor performance. Hindlimbs are key for maximal speed, but forelimb length was a better predictor for sustained speed (i.e. average speed over a total distance of 1.2 m). Finally, sustained speed differed among species with different diets, with herbivores running on average faster over a long distance than omnivores.

Climate change and lizards: changing species' geographic ranges in Patagonia

Ectothermic organisms strongly depend on temperature, making them an excellent model to study the impact of global climatic change (GCC). Under global warming, species may be forced to move toward colder environments, such as higher latitudes, higher elevations or both. However, several studies show that responses may vary significantly in different groups of species. Therefore, it is unclear whether species’ current distribution range sizes will be affected in future climatic scenarios. In addition to the specific possible effect of range size changes, the potential consequences of distributional range shifts also should be considered. Here, our aim is to assess whether GCC may affect a group of Liolaemus lizard species based on their current geographic distribution range size and whether the effect is uniform across all species using species distribution models (SDMs). Our results show that range boundaries of the fourteen species switch toward higher altitude and latitude in future scenarios. Additionally, there is not a unique pattern in terms of increase or decrease in potential range for lizards in Patagonia in future scenarios. Finally, our results show that the original distribution range size is determinant for the resultant SDMs projections, suggesting that species with a high degree of endemicity may be susceptible to a greater impact of GCC.

Climate, geographic distribution and Viviparity in Liolaemus (Reptilia; Squamata) species: when hypotheses need to be tested

(1) Laboratorio de Fotobiología, Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA), CONICET-UNCOMA, Quintral 1250, Bariloche, 8400 Río Negro, Argentina. (2) Department of Biology, 212 Clarkson Science Center, MRC 5805, 8 Clarkson Avenue, Clarkson University, NY. Estados Unidos. (3) Facultad de Ciencias Naturales e I. M. Lillo (UNT), CONICET-Instituto de Herpetología (FML), Tucumán, Argentina. Miguel Lillo 205, 4000, San Miguel de Tucumán, Argentina.

Effect of body mass and melanism on heat balance in Liolaemus lizards of the goetschi clade

ABSTRACT The body temperature of ectotherms depends on the environmental temperatures and behavioral adjustments, but morphology may also have an effect. For example, in colder environments, animals tend to be larger and to show higher thermal inertia, as proposed by Bergmanns rule and the heat balance hypothesis (HBH). Additionally, dark coloration increases solar radiation absorption and should accelerate heat gain (thermal melanism hypothesis, TMH). We tested Bergmanns rule, the HBH and the TMH within the Liolaemus goetschi lizard clade, which shows variability in body size and melanic coloration. We measured heating and cooling rates of live and euthanized animals, and tested how morphology and color affect these rates. Live organisms show less variable and faster heating rates compared with cooling rates, suggesting behavioral and/or physiological adjustments. Our results support Bergmanns rule and the HBH, as larger species show slower heating and cooling rates. However, we did not find a clear pattern to support the TMH. The influence of dorsal melanism on heating by radiation was masked by the body size effect in live animals, and results from euthanized individuals also showed no clear effects of melanism on heating rates. Comparison among three groups of live individuals with different degrees of melanism did not clarify the influence of melanism on heating rates. However, when euthanized animals from the same three groups were compared, we observed that darker euthanized animals actually heat faster than lighter ones, favoring the TMH. Although unresolved aspects remain, body size and coloration influenced heat exchange, suggesting complex thermoregulatory strategies in these lizards, probably regulated through physiology and behavior, which may allow these small lizards to inhabit harsh weather environments. Summary: Body size and coloration influence heat exchange in Liolaemus lizards, suggesting complex thermoregulatory strategies that are probably regulated through physiology and behavior, which may enable these small lizards to inhabit the harsh Patagonian environment.

Composición y riqueza de anfibios y sus relaciones con las características de los sitios de reproducción en un sector de la Selva Atlántica de Misiones, Argentina

Atlantic forest harbors a large number of endemic amphibian’s species. At present only 7.5 % of the Atlantic Forest original surface remains. In this study we compare frog’s species richness and assemblage composition between different types of reproductive habitats in a sector of the Atlantic Forest of Argentina. Surveys were made during four months in two consecutive years. Four reproductive habitats were surveyed: temporary ponds, pig wallows, temporary streams and permanent streams. Frogs species richness and composition and environmental descriptors were recorded in these habitats. Temporary ponds have the greatest richness. Anuran abundance shows associations with vegetation in the bodies of water. The results suggest that different types of wetlands exert differential pressures (e.g. predation, hidroperiod) on amphibian assemblages. Finally, we highlight the importance of small ponds and vegetation heterogeneity for anuran assemblages of the Atlantic Forest of Argentina.

How sensitive are temperate tadpoles to climate change? The use of thermal physiology and niche model tools to assess vulnerability

Ectotherms are vulnerable to climate change, given their dependence on temperature, and amphibians are particularly interesting because of their complex life cycle. Tadpoles may regulate their body temperature by using suitable thermal microhabitats. Thus, their physiological responses are the result of adjustment to the local thermal limits experienced in their ponds. We studied three anuran tadpole species present in Argentina and Chile: Pleurodema thaul and Pleurodema bufoninum that are seasonal and have broad geographic ranges, and Batrachyla taeniata, a geographically restricted species with overwintering tadpoles. Species with restricted distribution are more susceptible to climate change than species with broader distribution that may cope with potential climatic changes in the environments in which they occur. We aim to test whether these species can buffer the potential effects of climate warming. We used ecological niche models and the outcomes of their thermal attributes (critical thermal limits, optimal temperature, and locomotor performance breadth) as empirical evidence of their capacity. We found that Pleurodema species show broader performance curves, related to their occurrence, while the geographically restricted B. taeniata shows a narrower thermal breadth, but is faster in warmer conditions. The modeled distributions and empirical physiological results suggest no severe threats for these three anurans. However, the risk level is increasing and a retraction of their distribution range might be possible for Pleurodema species, and some local population extinctions may happen, particularly for the narrowly distributed B. taeniata.