Conectando biogeografia histórica e assembleias locais de aves de sub-bosque na Amazônia: áreas de endemismo, diversidade de espécies e proporcionalidade de guildas

Abstract

The patterns of diversity in biological communities reflects historical and contemporaneous events that occurs at different spatial scales. In the Amazon, there is a consensus that historical processes related to the establishment of the drainage and the terra firme forests had triggered events of vicariance, speciation and dispersal, determining the regional pool of species. In addition, local ecological factors such as resource availability and species interactions are important in maintaining historically established patterns. The areas of endemism are units of interpretation of historical biogeography and investigating the assemblages in these areas can enhance our knowledge about the interaction between historical events and local diversity. We investigated patterns of diversity, composition, and structuring of understory bird assemblages from upland forests in seven Amazonian areas of endemism, using data from birds captured by mist nets, provided by several researchers. Our research sought to understand if the historical effect that resulted in the delimitation of the endemic areas could be extrapolated to the whole bird assemblage, besides the endemic species, acting in the current patterns of diversity and species composition. We find out which guilds predominate in each AE and if there is guilds substitution between the AE. We also tested if exists guild proportionality in each endemic area. The patterns of diversity and species composition were distinct among the seven areas of endemism studied, both in richness and in the assemblages intrinsic composition considering all the species studied, as in the relative abundances of species widely distributed in the Amazon. The insectivorous guild was predominant in all areas and the proportion of species and individuals in the guilds was constant between the areas of endemism. There is a prevalence of alpha guilds (guild proportionality) in almost all investigated areas. The species substitution between the endemic areas does not occur in a random way and it maintains the same ecological functions of the species, indicating a relative homogeneity in the resources availability of the upland forests. The prevalence of alpha guilds indicates that interspecific competition is a strong structuring factor of local assemblages, probably in a process of limiting similarity in the body size of the species. The congruence between the structuring of the understory bird assemblages and the areas of endemism evidence how much historical and evolutionary processes that acts on a large scale, along with local ecological processes, lead to the current patterns of diversity and species composition in the Amazon.