Patterns and ecological correlates of pollination modes among bromeliad communities of Andean forests in Bolivia

We studied the distribution of five pollination modes (ornithophily, chirop terophily, entomophily, mixed/unspecific, autogamy) among the bromeliad com munities of 74 forest sites in the Bolivian Andes and adjacent lowlands. We recorded a total of 188 bromeliad species belonging to 16 genera, includin g 115 (61%) ornithophilous, 14 (7%) chiropterophilous, 45 (24%) entomophilo us, 8 (4%) autogamous, and 6 (3%) species with mixed pollination mode. Orni thophily was the dominant pollination mode at high elevations and in wet re gions, while entomophily dominated in arid regions. Chiropterophily was mos t common in wet lowland regions, autogamy in arid sites, and mixed pollinat ion in the lowlands. Pollination modes were rather evenly distributed among life-forms and ecophysiological types, with a few exceptions: terrestrial forest bromeliads, mostly belonging to unarmed, soft-leaved taxa, had a pre valence of entomophily and few ornithophilous species; large, spiny terrest rial bromeliads of Puya and Bromelioideae showed a prevalence of ornithophi ly; and autogamy was restricted to the neotenous subgenus Diaphoranthema of Tillandsia. The restriction of unspecific pollination modes to the lowland s is hypothesized to be related to the abundance of pollinators, eliminatin g the need for specialized co-evolution, or to the overall rarity of bromel iads in this environment, precluding the development of specialized relatio nships. The low representation of entomophilous species in small dry forest regions compared to extensive areas is assumed to be due to the seasonal i nflux of hummingbirds and/or bats. Overall, the frequency of individual pol lination modes was related to the availability of pollinators as determined by temperatures and humidity.