Climatic constraints and the distribution of Patagonian mice

We generated potential distribution models for 14 sigmodontine rodent species that inhabit the Andean–Patagonian forest region and adjacent areas, and retrieved the main climatic variables responsible for these models. Our main objective was to compare these climatic variables and the distribution patterns generated for each species, and explore the effects of the physical environment in shaping the composition of rodent communities in the area. We retrieved a total of 1,215 records of species presence from 580 sites. Maxent was used to generate potential distribution models for the 14 rodent species studied. We used a total of 20 variables obtained from the WorldClim database, including elevation and 19 bioclimatic variables, in addition to normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI). Our results showed a clear discrimination between two groups of rodents, one concentrated in the western part of our study area, with more humid climate and a rugged mountainous and discontinuous habitat, and another inhabiting the eastern, drier part of our study area, which appears to be more uniform in habitat characteristics. These groups showed a mosaic of phylogenetically non-related species from different tribes, that probably arrived or expanded into Patagonia during the last millennia. The overlap of all models showed the forest-steppe ecotone east of Nahuel Huapi Lake and south to −43° latitude as the area with the highest species richness (8–11 species). All species showed a high correspondence with temperature and precipitation that define patterns at a landscape scale, with little to very little information contained in the typical vegetation variables that would define local conditions.

En este trabajo generamos modelos de distribución potencial para cada especie de roedor sigmodontino que habita la región de los bosques andino-patagónicos y áreas adyacentes, identificando las principales variables climáticas que influyen en dichas distribuciones. Nuestro principal objetivo fue comparar las variables climáticas y los patrones de distribución generados para cada especie, y explorar los efectos del entorno físico en la composición de los ensambles de especies. Recopilamos un total de 1215 registros de presencia de especies de 580 sitios. Se utilizó MaxEnt para generar los modelos de distribución potencial de las 14 especies de roedores estudiadas, con 20 variables obtenidas de la base de datos WorldClim, incluida la elevación, 19 variables bioclimáticas, además del NDVI y EVI. Nuestros resultados muestran una clara discriminación entre dos grupos de roedores, uno concentrado en el área occidental, con un clima más húmedo y montañoso, y otro que habita en el área más seca del este. Curiosamente, estos grupos muestran un mosaico de especies, filogenéticamente no relacionadas y de diferentes tribus, que probablemente llegaron o se expandieron en la Patagonia durante los últimos milenios. La superposición de todos los modelos muestra el ecotono bosque-estepa, al este del lago Nahuel Huapi y hacia el sur hasta los -43°, como la zona más rica en especies (8 a 11 especies). Todas las especies muestran una alta correspondencia con las variables ambientales (temperatura y precipitación) que definen patrones a escala del paisaje, con muy poca información contenida en las variables típicas de la vegetación que definirían las condiciones locales.

Regional Extinctions and Quaternary Shifts in the Geographic Range of Lestodelphys halli, the Southernmost Living Marsupial: Clues for Its Conservation

The Patagonian opossum (Lestodelphys halli), the southernmost living marsupial, inhabits dry and open environments, mainly in the Patagonian steppe (between ~32°S and ~49°S). Its rich fossil record shows its occurrence further north in Central Argentina during the Quaternary. The paleoenvironmental meaning of the past distribution of L. halli has been mostly addressed in a subjective framework without an explicit connection with the climatic “space” currently occupied by this animal. Here, we assessed the potential distribution of this species and the changes occurred in its geographic range during late Pleistocene-Holocene times and linked the results obtained with conservation issues. To this end, we generated three potential distribution models with fossil records and three with current ones, using MaxEnt software. These models showed a decrease in the suitable habitat conditions for the species, highlighting a range shift from Central-Eastern to South-Western Argentina. Our results support that the presence of L. halli in the Pampean region during the Pleistocene-Holocene can be related to precipitation and temperature variables and that its current presence in Patagonia is more related to temperature and dominant soils. The models obtained suggest that the species has been experiencing a reduction in its geographic range since the middle Holocene, a process that is in accordance with a general increase in moisture and temperature in Central Argentina. Considering the findings of our work and the future scenario of global warming projected for Patagonia, we might expect a harsh impact on the distribution range of this opossum in the near future.