Species-poor and low-lying sites are more ecologically unique in a hyperdiverse Amazon region: Evidence from multiple taxonomic groups

Aim: We analysed beta-diversity patterns of various biological groups simultaneously, from the perspective of site ecological uniqueness. We also investigated whether ecological uniqueness variation could be explained by variations in environmental conditions and spatial variables. Data: Central Amazonia. Methods: We estimated the total beta diversity and ecological uniqueness for 14 biological groups, including plants and animals, sampled at the same sites on a mesoscale in central Amazonia, Brazil. The uniqueness values for all biological groups were combined in a single matrix (multi-taxa matrix of site uniqueness), which was then used as a response variable matrix in a partial redundancy analysis. We also investigated differences in the uniqueness patterns between plant and animal groups. Results: In general, plants showed higher total beta diversity than animals. For plants, uniqueness was explained mainly by environmental conditions, while for animals, uniqueness was also related to spatial variables. Although variation in uniqueness was mainly related to soil clay content, it is difficult to determine a single major environmental variable underlying the variation in uniqueness because the topographical gradient influences many of them, including soil clay content. Main Conclusion: The uniqueness values were higher in low-lying areas, indicating that near-stream sites were more ecologically unique. Despite the lower number of species in the lowlands, their unique biota contributed strongly to the maintenance of the total beta diversity of the area. This finding should be considered in conservation plans that aim to represent and preserve the regional biota. Our approach proved to be useful to analyse and compare the ecological uniqueness of multiple taxa.