Taxonomic, functional and phylogenetic beta diversity of upland forest birds in the Amazon: The relative importance of biogeographic regions, climate, and geographic distance

Aim: We address the relative importance of biogeographic regions (areas of
endemism), regional climate, and spatial factors on taxonomic, functional,
and phylogenetic β-diversity of bird assemblages in upland terra-firme
forests in the Amazon. Location: Amazon biome.
Taxon: Birds Methods: We gathered 27,498 occurrence
records of 873 bird species for 115 bird assemblages distributed in all
nine biogeographic regions delimited by the major Amazonian rivers. Only
data from studies surveying whole communities with standard sampling
methods and exhaustive sampling effort were included. We partitioned the
fractions of taxonomic, functional and phylogenetic beta diversity
explained by climate, biogeographic regions, spatial factors, and the
variation shared between them. Results: Across the entire Amazon,
we found higher total taxonomic (0.68±0.10) than phylogenetic (0.46±0.08)
β-diversity, and low functional β-diversity (0.34±0.08). Biogeographic
regions showed the highest unique contributions explaining taxonomic and
phylogenetic β-total (7% and 5%, respectively) and turnover components (7%
of β-jtu taxonomic, 7% of β-jtu phylogenetic), but accounted for only 2%
of total functional β-diversity and trait turnover. Climatic variables
explained slightly more trait nestedness (5%) compared to species and
lineage turnover (3% each). Species composition was clearly distinct
between biogeographical regions limited by the Amazon River, but support
for the effect of other rivers was mixed. Main conclusions: Our
study highlights the significant influence of biogeographic regions and
climate on species composition in the Amazon. However, our findings also
suggest that the Amazon River exerts a more pronounced impact on species
distribution compared to other major Amazonian rivers. Species turnover
across biogeographical regions is particularly evident at the species
level, with minor effects observed in functional traits, suggesting that
taxonomic turnover is driven mainly by functionally redundant species. In
addition, recent diversification events, predominantly occurring at the
tips of the phylogeny without substantial turnover at deeper nodes, are
likely responsible for the patchy distribution of species across Amazonia.