Is thermal sensitivity affected by predation risk? A case study in tadpoles from ephemeral environments.

Changes in environmental temperature may induce variations in thermal tolerance and sensitivity in ectotherm organisms. These variations generate plastic responses that can be analyzed by examining their Thermal Performance Curves (TPCs). Additionally, some performance traits, like locomotion, could be affected by other factors such as biological interactions (e.g., predator-prey interaction). Here, we evaluate if the risk of predation modifies TPCs in Mendoza four-eyed frog (Pleurodema nebulosum, Burmeister, 1861) and Guayapa's four-eyed frog (Pleurodema guayapae, Barrio, 1964), two amphibian species that occur in ephemeral ponds in arid environments. We measured thermal tolerances and maximum swimming velocity at six different temperatures in tadpoles under three situations: control, exposure to predator chemical cues, and exposure to conspecific alarm cues. TPCs were fitted using General Additive Mixed Models. We found that curves of tadpoles at risk of predation differed from those of control mainly in thermal sensitivity parameters. Our work confirms the importance of biotic interactions have in thermal physiology.

Chytridiomycosis in endemic amphibians of the mountain tops of the Córdoba and San Luis ranges, Argentina.

Chytridiomycosis is a major threat to amphibian conservation. In Argentina, the pathogenic fungus Batrachochytrium dendrobatidis has been recorded in several localities, and recently, it was registered in amphibians inhabiting low-elevation areas of mountain environments in Córdoba and San Luis provinces. In the present study, we searched for B. dendrobatidis in endemic and non-endemic amphibians on the mountain tops of Córdoba and San Luis provinces. We collected dead amphibians in the upper vegetation belt of the mountains of Córdoba and San Luis. Using standard histological techniques, the presence of fungal infection was confirmed in 5 species. Three of these species are endemic to the mountain tops of both provinces. Although there are no reported population declines in amphibians in these mountains, the presence of B. dendrobatidis in endemic species highlights the need for long-term monitoring plans in the area.

Climate change and American Bullfrog invasion: what could we expect in South America?

BACKGROUND: Biological invasion and climate change pose challenges to biodiversity conservation in the 21(st) century. Invasive species modify ecosystem structure and functioning and climatic changes are likely to produce invasive species' range shifts pushing some populations into protected areas. The American Bullfrog (Lithobates catesbeianus) is one of the hundred worst invasive species in the world. Native from the southeast of USA, it has colonized more than 75% of South America where it has been reported as a highly effective predator, competitor and vector of amphibian diseases. METHODOLOGY/PRINCIPAL FINDINGS: We modeled the potential distribution of the bullfrog in its native range based on different climate models and green-house gases emission scenarios, and projected the results onto South America for the years of 2050 and 2080. We also overlaid projected models onto the South American network of protected areas. Our results indicate a slight decrease in potential suitable area for bullfrog invasion, although protected areas will become more climatically suitable. Therefore, invasion of these sites is forecasted. CONCLUSION/SIGNIFICANCE: We provide new evidence supporting the vulnerability of the Atlantic Forest Biodiversity Hotspot to bullfrog invasion and call attention to optimal future climatic conditions of the Andean-Patagonian forest, eastern Paraguay, and northwestern Bolivia, where invasive populations have not been found yet. We recommend several management and policy strategies to control bullfrog invasion and argue that these would be possible if based on appropriate articulation among government agencies, NGOs, research institutions and civil society.