The reproductive success of hummingbird-pollinated plants often depends on complex interactions between environmental conditions and pollinator biology (Navarro 1999, Stiles 1985, Wolf et al. 1976). The effect of environment on reproductive success of hummingbird-pollinated plants is particularly pronounced at high altitudes, where large daily fluctuations in temperature, relative humidity and solar radiation limit the effective time for photosynthesis (Cavieres et al. 2000) and affect foraging activity (Navarro 1999) and abundance of pollinators (Rahbek 1997). At high altitudes in the tropical cloud forests of Costa Rica these factors may have serious impacts on fruit production.
