The influence of biogeographic and ecological heterogeneity on Amazonian pollen spectra

The influence of gamma- (gamma) and beta- (beta) diversity on modern pollen rain is assessed using data from three Amazonian forests. Pollen rain of 79 forest locations was collected in modified Oldfield pollen traps between 1991 and 1993. Pollen diversity in the traps was high with > 280 palynomorph types recognized. Gamma diversity was assessed by comparing lowland terra firme forests in Cuyabeno, Ecuador, with two terra firme forests near Manaus, Brazil. The influence of beta -diversity on local pollen rain was investigated using samples collected from neighbouring terra firme forests, seasonally flooded forests, and Mauritia-rich forests at Cuyabeno, Ecuador. Multivariate analyses revealed that gamma -diversity produces a stronger signal in the pollen rain than beta -diversity. However, beta -diversity is accurately reflected in the pollen rain when the diversity is an expression of strong environmental gradients.