Uso dos estratos verticais por pequenos mamíferos em formações florestais do cerrado brasileiro : padrões de diversidade, relação com a disponibilidade de recursos, seleção de hábitat e habilidade de locomoção arborícola das espécies

Abstract

The study of vertical stratification patterns by small mammals in the Cerrado is important due to the distinct characteristics among phytophysiognomies. Forest formations of this biome can present different degrees of complexity and differences related to seasonality and resource availability. Thus, habitat features contribute to different patterns of vertical stratification. In this study we evaluated the vertical stratification of rodents and marsupials in the cool-dry and warm-wet seasons in four areas of cerradao (dry-woodland) and four areas of gallery forest, installing live-traps on the ground, understory (1-4 m) and canopy (>7 m). We also verified fruit (by counting) and arthropod availability (using window traps and pitfalls), to evaluate how resource availability contributes to vertical stratification of small mammals. Among the 11 captured species, the marsupial Caluromys lanatus (in both physiognomies) was captured only in the canopy. The marsupial Monodelphis americana and the rodent Calomys expulsus were captured in cerradao, and the rodent Proechimys roberti in gallery forest, were captured only on the ground. Among the species that used the ground and understory, were the rodent Hylaeamys megacephalus (mainly terrestrial) and Oligoryzomys nigripes and O. fornesi (scansorial). The species that used the three vertical strata (in different intensities) were the marsupials Didelphis albiventris and Gracilinanus agilis, and the rodents Oecomys cf. roberti and Rhipidomys macrurus. Our results showed that R. macrurus used the canopy in greater intensity in the cerradao compared to gallery forest, and G. agilis used the ground and understory in greater intensity in the cool-dry season in both physiognomies. Additionally, we verified a relation between vertical strata utilization and availability of fruits (G. agilis, O. cf. roberti e R. macrurus), and biomass of arthropods (R. macrurus), coleopterans (O. cf. 27 roberti e R. macrurus), and lepidopterans (G. agilis). We also verified that in gallery forest, there is an increase in number of species considering different vertical strata, and also that beta diversity is more similar among strata than among areas. Our results indicate that different seasons and phytophysiognomies, and availability of resources are important factors to be considered in the vertical stratification patterns of different species and in the community of small mammals. However, our results also indicate that the patterns found in this study, are, to a certain degree, associated with environment complexity, probably due to the greater opportunities of niche segregation.