Diversidade beta de aves de sub-bosque em um arquipélago de ilhas florestais artificiais na Amazônia

Abstract

Anthropogenic disturbances such as the loss, fragmentation, and degradation of natural habitats have led to significant changes in the composition of biological communities and the distribution of biodiversity. Beta diversity is a central metric for assessing these changes, as it reflects variation in species composition among sites. More recently, the concept has been expanded to include functional and phylogenetic dimensions, allowing for a more comprehensive understanding of the ecological processes underlying community organization. Nevertheless, most studies remain limited to the taxonomic dimension, which may obscure important ecological patterns. In the Amazon, a region of high biodiversity shaped by substantial environmental heterogeneity, the intensification of anthropogenic impacts such as deforestation, agricultural expansion and especially the construction of hydroelectric dams has led to profound ecological changes. Hydroelectric dams in particular promote forest insularization by fragmenting large continuous forest areas into small remnants isolated by water. In this context, investigating how beta diversity, across its multiple dimensions, responds to insularization is essential for guiding effective and integrated conservation strategies. Here we investigated the taxonomic and functional beta diversity of understory birds in an archipelago of artificial forest islands, assessing the effects of island area and isolation on beta diversity components and inferring the ecological processes shaping these communities. The study was conducted in the Balbina Hydroelectric Reservoir (Amazonas, Brazil), formed by the damming of the Uatumã River. We sampled a total of 32 islands and five continuous forest sites using mist nets to capture birds. With a sampling effort of 21,312 net-hours, we captured 1,636 individuals belonging to 114 species. Both taxonomic and functional beta diversity were higher on islands compared to 10 continuous forest, indicating that insularization increases compositional variation among communities, primarily due to differences in species richness. Island area and isolation significantly influenced beta diversity, contributing to increased taxonomic and functional richness differences among sites. These patterns suggest that selective local extinctions and dispersal limitations are key processes in community organization. Despite the increase in beta diversity, this outcome stems from the loss of species and ecological functions, which may compromise functional integrity and ecosystem services. Thus, our findings highlight the need for conservation strategies that preserve both taxonomic and functional diversity, prioritizing fragment connectivity and size to mitigate the negative impacts of insularization in the Amazon. Keywords: avifauna, insularization, hydroelectric dams, island biogeography, selective extinction, dispersal limitation.