Small mammals of the Atlantic Forest of the Atlantic Plateau of São Paulo: an evaluation of the threat of extinction and the response to alterations in context and remnant size / Pequenos mamíferos da Mata Atlântica do Planalto Atlântico Paulista: uma avaliação da ameaça de extinção e da resposta a alterações no contexto e tamanho dos remanescentes

AUTOR(ES)

Adriana de Arruda Bueno

DATA DE PUBLICAÇÃO

2008

RESUMO

A long-term standardized survey of the Atlantic Forest small mammals was conducted using pitfall traps in 68 sites distributed in six 10.000-ha landscapes (three in continuous forest and three in fragmented landscapes) located in three regions in the Atlantic Plateau of São Paulo. The fragmented landscapes harbored different amounts of remnants, 50%, 30% and 10%, percentages above or within the superior and inferior limits of the theoretical fragmentation threshold (10-30%). This thesis was divided in four chapters e two main approaches. The first approach (Chapter 2) aimed to evaluate if small mammals listed as threatened were affected by forest fragmentation and quality in the Atlantic Plateau of São Paulo state. For this, we used data from 68 sites distributed in eight categories: nine in mature continuous forests, nine in secondary continuous forests, four in large and 11 in small patches in the landscape with 50% of remnants, seven in large and 13 in small patches in the landscape with 30% of remnants and four in large and 11 in small patches in the landscape with 10% of remnants. We investigated if 10 threatened small mammals and five non-threatened endemic species commonly found in continuous forests were equally affected by fragmentation, at the landscape and patch scales, and by forest quality. Regardless of threat or rarity level, no analyzed species responded to differences in the regeneration stage in continuous forests. On the other hand, our data showed that common endemic species respond more strongly and negatively to the loss and fragmentation of the Atlantic Forest than threatened species, which either may not be affected by fragmentation, or be positively or negatively affected. we suggest separating species in two groups (naturally rare versus affected by human impact) in the Red Lists and including different criteria to evaluate common species such as response to habitat loss and fragmentation as well as habitat specificity in terms of endemism and level of matrix tolerance. The second approach (Chapter 3) aimed to evaluate the effects of context (landscape) and patch area in landscapes with different amounts of remnants on the richness and abundance of the endemic and non-endemic species. We used data from 50 sites located in the three fragmented landscapes. By analyzing the plausibility of eight regression models, which express alternative theoretical hypothesis about the importance of context and patch area, we investigate if the positive influence of patch area was stronger (1) for endemic species and (2) in the landscape within the superior limit of the fragmentation threshold (sensu Andrén, 1994), since in a context of high proportion of remnants, small and large patches could harbor viable populations and in a context of low proportion of remnants, sensitive species would have gone extinct. Except for the non116 endemic species richness, the models including context were the most plausible hypothesis to describe small mammal richness and abundance variations. As expected, the positive influence of patch area was more important in the landscape with 30% of remnants for the majority of the endemic small mammals, whereas the models including patch area were not among the most plausible ones for the non-endemic species. Our data corroborate the existence of a fragmentation threshold and point out that, although thresholds vary among species, it is possible to identify groups with similar response to habitat loss and fragmentation, directing management and conservation policies.

ASSUNTO(S)

conservação da biodiversidade biodiversity conservation limiares ecológicos habitat fragmentation lista de fauna ameaçada ecological thresholds endangered species fragmentação de habitat

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