Population dynamics and biodiversity of small mammals in treefall gaps within an Amazonian rainforest

In chapter 1, I investigate the role of heterogeneous landscapes and its effects on the population structure and dynamics of small mammals. Theory provides several models, including ideal free distribution and source-sink dynamics, to predict how individuals may respond to heterogeneity. Ecologists used the treefall gaps-understorey matrix as a model system to test how tropical plant and animal populations respond to a heterogeneous landscape. Studies found higher resources in the gap canopy than in the understorey, which was linked to higher animal densities than in the understorey. Gaps may be a superior habitat or even a source habitat while the understorey can represent a sink. However, no study has quantified whether of not resource availability at the ground level differs between these habitats and its consequences for terrestrial animals. In Chapter one, I addressed these questions in the Amazon by quantifying the resource availability in both habitats and measured the demographic and dispersal responses of two terrestrial rodent species.In chapter 2, I focus on mechanisms which may influences mammalian diversity in the tropics. The highest biodiversity is found at low latitudes, peaking in the tropics. Ecologists have focused on global and local scales in investigating the underlying mechanisms for this pattern. At a local scale, the intermediate disturbance hypothesis states that disturbances prevent competitive exclusions, thereby leading to higher diversity. I tested this hypothesis for terrestrial and arboreal small mammal communities in gaps and understorey habitats within an Amazonian rain forest.In chapter 3, I examined the effects of fruit and seed resource availability in treefall gap and understorey habitats on biomass and species diversity of terrestrial arthropods in a Peruvian Amazon rainforest. I quantified resource availability and arthropod biomass for six arthropod taxa (Arachnida, Formicidae, Coleoptera, Blattaria, Orthoptera, Diplopoda) and one miscellaneous group in six treefall gaps and understorey control sites over one year. Additionally, I collected data on morphospecies diversity for three taxa (Arachnida, Formicidae, and Coleoptera). Results indicated no difference in fruit and seed availability between gaps and understorey but both habitats exhibited significant seasonal variation. Also, I found similar arthropod biomass in gaps and understorey. Furthermore, species richness was similar in gaps and understorey. (Abstract shortened by UMI.