Predicting impacts of climate change using ensemble forecasting for the striped treefrog (Hypsiboas caingua) in South America

Background/Question/Methods

Although there is a crescent literature regarding Species Distribution Modelling (SDM) and future predictions of organisms under global warming effects, few studies are available for amphibians in the Brazilian hotsposts Cerrado and Atlantic forest. In this study I hypothesize that current climatic conditions can be used as a background to generate the future range distribution, considering the global warming scenario, of the striped treefrog (Hypsiboas caingua), a poorly known frog with discontinuous distribution within the Cerrado and Atlantic forest South American domains. The range distribution of H. caingua was modeled as a function of 23 literature records and seven bioclimatic variables that describe general climate trends (mean values of precipitation and temperature at each point occurrence) and potential physiological limits (variation of temperature and precipitation over time) for the occurrence of the species. Current and future potential distributions (2050 and 2080) were generated using three modelling methods, four Atmosphere-Ocean Global Circulation Models (AOGCM), and two CO₂ emission scenarios (A1 ‘pessimist’ and B1 ‘optimistic’ scenarios). Owing to inherent differences found among the SDM methods, different AOGCM databases, and CO₂emission scenarios, ensemble forecasts considering the consensus of all models were determined for each time slice as the final prediction maps.

Results/Conclusions

Although the scientific literature suggests that H. caingua presents a discontinuous distribution (Argentinian provinces of Misiones and Corrientes and adjacent areas in Paraguay, and further isolated populations in southeastern and southern Brazil), the SDM methods show that its current potential distribution is continuous along the occurrence records except for the low probability occurrence area between the Brazilian states of Rio Grande do Sul and central Paraná (southern Brazil). This suggests that the current gap on the distribution is due to the lack of anuran surveys in those regions. However, well surveyed sites among those known occurrences have no record for the striped treefrog, which suggests that other factors than climate might be also responsible for delimiting its range distribution. In 2050 H. caingua is presumed to reduce its total potential distribution area in ~10.1%, with an associated southeastward range shift. It is also expected an additional ~11.6% range contraction in 2080, which accounts for a total of ~21,7% loss of suitable occurrence area. Finally, the range distribution of H. caingua is expected to be mostly associated to the Atlantic forest hotspot, since its current Cerrado suitable areas will be presumably lost under the global warming scenario.