Niche breadth of oligarchic species in Amazonian and Andean rain forests

Abstract

Aim To test the niche breadth hypothesis (NBH), which states that dominant species have broader environmental tolerances than rare species, focusing on oligarchic species distributions (1) along the gradients of edaphic and climatic individual variables, and (2) within the n‐dimensional environmental frame defined by all edaphic and climatic variability. Location Amazonian and Andean tropical rain forests along a ca. 3000 m elevation gradient, covering an area of 200 × 200 km in northwestern Bolivia. Methods All woody plants with a DBH ≥2.5 cm were measured in 98 0.1‐ha plots. We analysed 18 chemical properties of the soils in each plot. Climatic and topographic variables were obtained from available open‐access databases. Three measures were calculated for each of the species found at each forest type: (1) regional‐scale dominance based on frequency and local abundance, (2) niche breadth along each of the environmental variables, and (3) total niche size within the whole environment. Results Oligarchic species showed broader niche breadths than the other species that constituted the community assembly in both Amazonian and Andean rain forests. The niche breadth of any species tended to be positively correlated with its degree of dominance. The Amazonian forest showed a stronger oligarchic pattern than the Andean forest, and the Amazonian common species showed larger niches overall. However, this pattern differed for some particular variables: Amazonian oligarchies had narrower niches along the variables related to organic matter and most climatic variables, whereas Andean oligarchies had narrower niches along several micronutrient factors and temperature variables. Conclusions The results provide strong empirical support for the NBH in tropical rain forests. However, different patterns of dominance were found in the two habitats: oligarchic species ranged from narrow‐niched species to very broad generalist species. Broad‐niched oligarchic species have also been reported in other regions, suggesting an important role of niche size linking commonness at different scales. Oligarchic species exhibit relatively narrow niches with respect to soil factors if measured along wide gradients, regardless of the forest type studied. In contrast, the opposite pattern was found for many climatic variables, indicating higher sensitivity to climate in Amazonia compared to the Andes. Despite these differences, Amazonia has much larger total niche sizes for its common species than the Andes overall.

Climatic and edaphic controls over tropical forest diversity and vegetation carbon storage

“…Landscape-scale variation in functional community composition results from local-scale specialization of a given species in response to its climate envelope and the filtering of the locally available species pool by physical and chemical soil properties 39 . We here found differences in plant functional community composition across topoedaphic gradients and more generally that sites with lower resource availability contained less diverse plant www.nature.com/scientificreports www.nature.com/scientificreports/ communities than those with ample soil water and nutrient supply ( Fig.…”

Climatic niche breadth can explain variation in geographical range size of alpine and subalpine plants

“…Since this hypothesis was proposed by Stevens (1989), it has been confirmed by a number of studies. More recent studies have used the term 'climatic niche breadth' rather than 'climatic variability' to illustrate the ability (range) that can be tolerated by one species (Fisher-Reid et al 2012, Köster et al 2013, Arellano et al 2014. showed that climatic niche breadth, which is the range of climatic condition a species occurs in, explained more variation than the niche position, which is a species' niche relative to the central tendency of climatic conditions in a study region for the geographical range size of monkeyflower species (genus Mimulus).…”

Beta diversity and oligarchic dominance in the tropical forests of Southern Costa Rica

“…(), which reported a consistent pattern of dominance by a relatively small but abundant set of tree and palm species, called “oligarchs”, in the upland tropical forests of eastern Ecuador and southern Peru. Since then, evidence has accumulated reinforcing the existence of a general pattern of oligarchic dominance in tropical forest, especially in the neotropics (Svenning, Kinner, Stallard, Engelbrecht & Wright, ; Vormisto, Svenning, Hall & Balslev, ; Macía & Svenning, ; Williams, Viers & Schwart, ; Williams, Trejo & Schwart, ; Macía, ; Arellano, Cala & Macía, ; Arellano et al., ; see Pitman, Silman & Terborgh, ; for a detailed review), whereas “oligarch” refers to abundant and frequent species at regional‐landscape level, “hyperdominant” defines species very abundant and frequent at large geographical scales (e.g., the Amazon basin). Practical implications of the so‐called oligarchic dominance would drastically simplify model parameterization of trophic interactions and critical ecosystem services, such as water, carbon, and nutrient cycling (ter Steege et al., ).…”

“…Finally, (3) oligarchies are mainly structured by the same niche mechanisms that generate spatial heterogeneity in tree species composition and abundance (Pitman et al., ). Oligarch species usually show broader environmental tolerances than less common ones (Arellano et al., ; Brown, ; Phillips et al., ; Slatyer, Hirst & Sexton, ), but they are not necessarily indifferent to environmental heterogeneity, showing higher abundances in the most favorable habitats (ter Steege et al., ). As a result, beta diversity will increase with environmental heterogeneity, but this increase is mainly driven by differences in oligarchic abundance and not by turnover in species identity.…”

“…On the one hand, propagule limited dispersion and successful recruitment close to conspecifics produce clustered distributions of populations and contribute to community similarity and characterization of oligarch patterns at local scales (de Cáceres et al., ; Chain‐Guadarrama, Finegan, Vilchez & Casanoves, ). On the other hand, niche differentiation and environmental gradients determine competitive abilities and dominance hierarchies, structuring oligarch communities in space (Arellano et al., , ; de Cáceres et al., ; Pitman et al., ; Prada & Stevenson, ; Sesnie, Finegan, Gessler & Ramos, ). Whereas most of the studies have shown that both mechanisms contribute to changes in community composition (Baldeck et al., ; de Cáceres et al., ; Chain‐Guadarrama et al., ; Condit et al., ; Legendre et al., ; Prada & Stevenson, ; Vormisto et al., ), more work is needed to understand how variation in geographical scale affects the partitioning of beta diversity.…”