María Gabriela Perotti

Estado del conocimiento de humedales del norte patagónico (Argentina): aspectos relevantes e importancia para la conservación de la biodiversidad regional

Las areas de humedal ocupan casi el 5 % del territorio de la Patagonia argentina. En la zona extrandina y el desierto patagonico estos ecosistemas son esenciales para sostener numerosas especies de fauna y flora silvestre. Ademas, los humedales del norte patagonico permiten el desarrollo de comunidades acuaticas complejas y constituyen el habitat critico de grupos de organismos como los peces y los anfibios incluidos en listados de conservacion prioritaria. Estos ecosistemas tienen un funcionamiento complejo que depende estrechamente de las fluctuaciones de las variables meteorologicas y son por lo tanto muy sensibles a los efectos del cambio climatico. En la actualidad el uso de la tierra, la introduccion de especies y la interaccion de estos aspectos con el cambio climatico constituyen las variables de mayor impacto sobre estos ambientes patagonicos. En este trabajo se presenta informacion geografica, geomorfologica y climatica de un numero de humedales del norte de la Patagonia argentina. Por otra parte, se sintetiza informacion sobre la flora y la distribucion de peces y anfibios con el proposito de enfatizar la importancia de estos ambientes en el mantenimiento de la biodiversidad regional. Por ultimo, se senalan los procesos que actualmente afectan a estos sistemas poniendo en evidencia la necesidad de obtencion de conocimientos basicos para el diseno de planes de manejo y conservacion de sus comunidades biologicas

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.

Toad Tadpole Responses to Predator Risk: Ontogenetic Change between Constitutive and Inducible Defenses

Abstract Rhinella spinulosa is a toad common in rivers, streams, and steppe wetlands where they face a variety of insect predators. Rhinella spinulosa tadpoles are known to be unpalatable to dragonfly naiads at some developmental stages. In this paper, we studied susceptibility of R. spinulosa tadpoles to predation by two species of predators, water bugs (Belostoma bifoveolatum, Belostomidae) with piercing-sucking mouth parts and dragonfly larvae (Rhionaeschna variegata, Aeshnidae) with chewing mouth parts. We conducted feeding trials to test the effectiveness of tadpole chemical defenses against water bugs. We also performed behavioral and choice experiments to study whether tadpole behavior influences their vulnerability to predators, and whether R. variegata has the capacity of discern between palatable (stages 38–45) and unpalatable tadpoles (stages 24–26). Rhinella spinulosa tadpoles, when fully palatable, responded by reducing their activity levels in the presence of dragonfly larvae but did not alter their behavior at unpalatable-early stages. Chemical defenses were not effective against the sucking predator (B. bifoveolatum) and no changes in tadpole activity were observed. Selectivity experiments revealed the ability of dragonfly larvae to distinguish between unpalatable and palatable tadpoles. Inducible (behavior) and constitutive (toxins) defenses observed in R. spinulosa tadpoles and the transition between them could result in an important survival mechanism in response to variable predator risk in the habitats in which they co-occur.

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.

Predatory insects in lentic freshwater habitats from northwest Patagonia: richness and phenology

The main purpose of this work was to study the richness, phenology and abundance of predatory insects throughout the hydroperiod and how they relate to the environmental parameters in lentic bodies of water in northwest Patagonia. Nineteen fishless wetlands and three wetlands with fish were studied, which are located in the surroundings of the Nahuel Huapi National Park. Biotic and abiotic variables were measured during the hydroperiod of each wetland. The dip-netting sampling technique was used to determine the richness of predatory insects and to study the phenology of the dominant species in four wetlands. Species richness in temporary wetlands ranged from one to nine species per wetland and does not differ from that observed in the permanent environments with or without fish predators. Maximum insect richness was recorded in late spring and was associated with the maximum depth of the wetland and its structural complexity as well as with the duration of the hydroperiod.

Potential distribution of Batrachochytrium dendrobatidis in Argentina: implications in amphibian conservation

Within the last two decades Batrachochytrium dendrobatidis (B.d.), the causative agent of chytridiomycosis, seems to have become a pandemic parasite, and is proposed as one of the more important causes of amphibian declines worldwide. In Argentina, the first report was in 2002 in Leptodactylus ocellatus. Since then, the fungus has expanded through different environments and species. In this study, we predict B.d. distribution in Argentina applying niche modelling based on reports of infected amphibians and environmental variables. The distribution hypothesis showed regions with highest suitability for B.d. including habitat types with (1) the most diverse amphibian fauna in Argentina such as the Paraná River Basin, (2) endangered species, such as north Patagonia and northwest Andean highlands, and (3) wide range of optimum precipitation and temperatures allowing development of B.d.

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.

Distribution of backswimmers in shallow ponds of Patagonia and their predatory role on a common tadpole–copepod assemblage

In this study, the distribution and occurrence of backswimmers in 21 fishless ponds was analysed in the Nahuel Huapi National Park (Patagonia, Argentina). We performed laboratory experiments to study the impact of different developmental stages of the endemic backswimmer Notonecta vereertbruggheni on typical co-occurring prey. We recorded three species of backswimmers N. vereertbruggheni, Notonecta virescens and Notonecta fazi. A seasonal study in Fantasma pond showed that adults of N. vereertbruggheni colonise and reproduce in the pond in spring and summer, co-occurring with other macroinvertebrates and endemic tadpoles. Predation experiments explored the impact of N. vereertbruggheni on two large co-occurring prey, the calanoid copepod Parabroteas sarsi and the tadpoles of Pleurodema thaul. The backswimmer consumed more copepods than tadpoles when prey was offered separately. Selectivity experiments demonstrated that the copepods were preferred over the tadpoles. Backswimmers may impact the typical assemblages of organisms found in fishless ponds of Patagonia during spring and summer.

Dramatic decline and range contraction of the Endangered Patagonian frog Atelognathus patagonicus (Anura, Leptodactylidae).

The Endangered frog Atelognathus patagonicus is endemic to the Laguna Blanca wetland system, Patagonia, Argentina. This species has undergone a significant contraction of its original distribution, including loss of the main population from the largest lagoon, Blanca. The decline of A. patagonicus was first perceived in 1986 and was thought to be at least partially associated with the anthropogenic introduction of the perch Percichthys colhuapiensis for sport. To evaluate the potential impact of P. colhuapiensis on A. patagonicus we surveyed for both species in 28 lagoons, and found A. patagonicus present in 23. These lagoons represent, however, only a small percentage of the total wetland area. The presence of A. patagonicus was associated with lagoons characterized by absence of P. colhuapiensis and high abundance of macrophytes. The most severe problem facing the remaining populations is in the many lagoons currently not protected by Laguna Blanca National Park. Conservation efforts need to focus on the prevention of fish introductions in the wetlands areas on private land. A project to restore A. patagonicus to Laguna Blanca, and educational programmes emphasizing the protection of Patagonian wetlands as reservoirs of regional biodiversity, are currently under development.

Lack of functional link in the tadpole morphology induced by predators

Abstract Most studies of predator-induced plasticity have focused on documenting how prey species respond to predators by modifying phenotypic traits and how traits correlate with fitness. We have previously shown that Pleurodema thaul tadpoles exposed to the dragonfly Rhionaeschna variegata responded strongly by showing morphological changes, less activity, and better survival than non-exposed tadpoles. Here, we tested whether there is a functional link between morphological plasticity and increased survival in the presence of predators. Tadpoles that experienced predation risk were smaller, less developed, and much less active than tadpoles without this experience. Burst speed did not correlate significantly with morphological changes and predator-induced deeper tails did not act as a lure to divert predator strikes away from the head. Although we have previously found that tadpoles with predator-induced morphology survive better under a direct predator threat, our results on the functional link between morphology and fitness are not conclusive. Our results suggest that in P. thaul tadpoles (1) burst speed is not important to evade predators, (2) those exposed to predators reduce their activity, and (3) morphological changes do not divert predator attacks away from areas that compromise tadpole survivalEE. Our results show that morphological changes in P. thaul tadpoles do not explain burst speed or lure attraction, although there was a clear reduction of activity, which itself reduces predation. We propose that changes in tadpole activity could be further analyzed from another perspective, with morphological change as an indirect product of behavior mediated by physiological mechanisms.