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

Recent studies have reported a consistent pattern of strong dominance of a small subset of tree species in Neotropical forests. These species have been called ‘hyperdominant’ at large geographical scales and ‘oligarchs’ at regional-landscape scales when being abundant and frequent. Forest community assembly is shaped by environmental factors and stochastic processes, but so far the contribution of oligarchic species to the variation of community composition (i.e. beta diversity) remains poorly known. To that end, we established 20 1-ha plots, i.e. 5 sites with 4 forest types (ridge, slope and ravine primary forest, and secondary forest) per site, in humid lowland tropical forests of southwestern Costa Rica to (1) investigate how community composition responds to differences in topography, successional stage and distance among plots for different groups of species (all, oligarch, common and rare/very rare species) and (2) identify oligarch species characterizing changes in community comp...