Beta diversity and microhabitat use of ant assemblages in a white-sand vegetation gradient in central Amazonia.

Much of the remarkable beta diversity of the Amazon biome is associated with the variety of vegetation types and other broad environmental gradients. We investigated ant assemblages in white-sand vegetation, one of the most distinctive vegetation types in the Amazon. Using pitfall traps in trees and on the ground, we comprehensively surveyed the ant assemblages along a natural gradient of vegetation structure, quantified with ground-LiDAR measurements. We collected individuals of 212 ant species/morphospecies distributed across 53 genera and nine subfamilies. Alpha diversity was not correlated with vegetation complexity, but beta diversity varied widely along the vegetation gradient. Species replacement was the predominant beta-diversity component, with smaller contributions from richness differences and nestedness. Terrestrial species composition was affected by vegetation structure, but arboreal species were more uniformly distributed along the vegetation-complexity gradient. Many habitat-generalist species (sampled in terrestrial and arboreal stratum) were sampled in less-complex parts of the gradient, suggesting that vertical stratification is diluted in more open vegetation. Our data indicate that the high species replacement in a small area increases the conservation value of this vegetation type by allowing much greater overall diversity than would be predicted by local alpha diversity. Implications for insect conservation: Our study demonstrates a remarkable ant-species replacement along a gradient of white-sand vegetation and highlights the importance of conserving this fragile environment, which is threatened by fire, deforestation, and mining. [ABSTRACT FROM AUTHOR]