Microhabitat specialization in a species-rich palm community in Amazonian Ecuador

1 Relationships between microhabitat variables (altitude, inclination, topographic position, drainage, canopy height) and the distribution and abundance of palms and palm-like plants in 50 ha of old-growth terra firme rain forest in the Yasuni National Park, lowland Amazonian Ecuador, were examined using 118 20 x 20 m plots laid out in a stratified random design. 2 If microhabitat niche differentiation is important for maintaining the species richness of the community, then (i) the distribution of the palms will be strongly influenced by microhabitat heterogeneity and (ii) palms of similar growth form will show antagonistic microhabitat relationships. 3 Mantel and cluster analyses showed that palm species distributions were strongly structured by topography. The main difference in species composition was between plots in the bottomland and plots on the upper slopes and hill tops. 4 Logistic and legit analyses showed that 20 of the 31 palm and palm-like taxa analysed had distributions that were significantly related to the microhabitat variables measured, mainly to topography but also to drainage and canopy height. 5 Spatial autocorrelation in the overall community structure was not explained by the microhabitat variables. Analyses of distributions or abundances of single species showed neighbourhood effects for seven taxa. 6 Antagonistic patterns of microhabitat preferences were recognizable among some species pairs of small palms, medium-sized palms and palm-like plants, but not among canopy palms. 7 It is concluded that microhabitat specialization is an important factor in maintaining the diversity of this palm community, while mass effects might also be important.