Oligarchies in Amazonian tree communities: a ten‐year review

Abstract

Th is paper revisits various hypotheses about oligarchic patterns in Amazonian tree communities put forward by Pitman et al. (2001). Together, these hypotheses predict that most lowland sites in the Amazon are located within large patches of relatively homogeneous edaphic and other environmental conditions, where an oligarchy of common, frequent tree species accounts for a majority of trees. To assess the degree to which these hypotheses have been corroborated or refuted over the last ten years, we reviewed Ͼ 200 studies published since 2001. We found overwhelming support for the hypothesis that large-scale oligarchies of common and frequent species are a common feature of Amazonian tree communities. At least 22 studies have documented oligarchies in Amazonian woody plant communities to date, and no studies have looked for oligarchies as defi ned by Pitman et al. (2001) and failed to fi nd them. We argue that six publications that off er critiques of the oligarchy hypothesis do not constitute valid tests. Th e other hypotheses in Pitman et al. (2001) -one regarding the specifi c oligarchic taxa that dominate forests near the eastern base of the Andes and one that attempts to explain why oligarchic species exist -are less well supported by the literature, in large part because they have not been subjected to many tests. We discuss links between these hypotheses and other well-known patterns and hypotheses in ecology (the abundance -occupancy relationship, the Janzen -Connell hypothesis, the niche-environment hypothesis, and the niche breadth hypothesis), and provide additional detail to facilitate rigorous tests in the future. Th e paper concludes by presenting remote sensing evidence that large patches of relatively homogeneous environmental conditions account for most of the upland forest landscape across Amazonian Peru.

Commonness and rarity determinants of woody plants in different types of tropical forests

“…1). Our results add to past studies reporting such a positive abundance-frequency relationship at different scales on tropical woody plants, the so-called oligarchic pattern (reviewed by Pitman et al 2013). Although such relationships have been found to be stronger within a given region or habitat, a positive relationship between abundance and spatial distribution of species is one of the most general patterns in ecology at any scale (Gaston et al 2000), strongly suggesting tight links from local and landscape commonness at \20,000 km 2 to regional and continental commonness at [2,000,000 km 2 (Kristiansen et al 2009;ter Steege et al 2013).…”

Biogeographic Barriers in the Andes: Is the Amotape—Huancabamba Zone a Dispersal Barrier for Dry Forest Plants?

“…The abundance of exclusive species was two to three times as high as the abundance of shared species (Quintana et al, 2017). The patterns found in DIAVs, with the majority of species shared with neighboring habitats but the minority of ecological specialized species as dominants in terms of abundance, has also recently been documented for palm swamp forests (Pitman et al, 2013) and white sand forests (García-Villacorta et al, 2016) in Amazonia. Dispersal from neighboring ecosystems is fundamental in shaping DIAV species composition, which is also true for Amazonian forests, where dispersal from non-white sand forests is fundamental in DIAVs located in the northern limits of the AmotapeHuancabamba zone have the highest numbers of species endemic to Ecuador.…”

Patterns of Medicinal Use of Palms Across Northwestern South America

“…These species are often trees that are relatively abundant in the different habitats due to their ecological amplitude (Macía & Svenning, 2005;Pitman et al, 2013, Cámara-Leret et al, 2014b and plant parts such as fruits, seeds and roots that are easily collected (de Medeiros et al, 2013). Additionally, in some cases the preference for these species may also be linked to their proven efficacy, e.g.…”