Niche breadth of oligarchic species in Amazonian and Andean rain forests

作者：Arellano Gabriel^*; Cala Victoria; Macia Manuel J

来源：Journal of Vegetation Science, 2014, 25(6): 1355-1366.

DOI：10.1111/jvs.12180

• Climatic niche
• Commonness
• Edaphic niche
• Environmental heterogeneity
• h index
• Niche breadth hypothesis
• Oligarchy hypothesis
• Rarity
• Species dominance
• Tropical rain forests

AimTo 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.
LocationAmazonian and Andean tropical rain forests along a ca. 3000m elevation gradient, covering an area of 200x200km in northwestern Bolivia.
MethodsAll woody plants with a DBH 2.5cm 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.
ResultsOligarchic 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.
ConclusionsThe 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.

• 出版日期2014-11