Variação do tamanho corporal em pequenos mamíferos neotropicais

Abstract

With this study we aim to examine the ecogeographic patterns of body size variation in populations of small mammals of the Atlantic Forest in eastern South America. For this we use body mass data from a mammal morphological trait dataset. The analyses comprise data for 8 species of marsupials and rodents, with adequate sampling throughout their distributions. We used linear regression analyses between body size and four predictor variables, accounting for the two main ecogeographic hypotheses, Bergmann’s and Resource rules. Considering the eight species studied, three marsupial species showed larger body sizes at lower latitudes, corresponding to the converse of Bergmann, and two rodent species follow Bergmann’s rule. Three marsupial species that present a significant and negative relationship with latitude also show an increase in size towards sites with higher mean temperatures. Conversely, the same occurs for two rodent species whose sizes increase with latitude but at lower temperatures. Regarding the resource hypothesis, three rodent species showed positive relationships with precipitation and one species with net primary productivity. Overall, marsupial species showed negative relationships with net primary productivity, decreasing body mass in more productive sites. Our results shed light into the divergent responses of marsupial and rodent species to ecogeographic rules. While some species follow Bergmann’s or Resource’s rules, we acknowledge that there are other environment or neutral factors determining the size variation in small mammals other than common predictors such as temperature, precipitation, and net primary productivity.