Pollination specialization and time of pollination on a tropical Venezuelan plain: Variations in time and space

Abstract

Levels of specialization of the pollination systems were evaluated in 155 plant species from the Venezuelan Central Plain. In all, 29 pollination systems were found, resulting from various combinations of nine pollen-vector types or pollinating agent classes. The number of pollen-vector types composing a pollination system ranged from one to five. Ninety-one species were pollinated by only a single pollen-vector type; the frequency of pollination systems fell monotonically with increasing number of constituent pollen-vector types. Some 30-40 per cent of bee-, moth-, beetle- and bat-pollinated species were pollinated by that group of vectors alone. The highest incidence of co-occurrence between pollen-vector types was found for the combinations fly-wasp, butterfly-wasp, butterfly-fly, and to a lesser extent bird-butterfly, bat-bird, bat-moth and butterfly-moth. The average number of pollen-vector types per plant species was significantly higher for trees and shrubs than for lianas and perennial herbs. The distribution of polyphily, oligophily, monophily and anemophily was significantly associated with life form and habitat. The relative frequencies of these types varied least through the year in the forest-savannah ecotone and in the vegetation as a whole, reflecting the combination of life forms. There were significantly fewer night-pollinated than day-pollinated species. Day-pollinated species tended to be polyphilous, and most of the night-pollinated species were monophilous or oligophilous. Time of pollination activity was related to habitat. The relative importance of night pollination among life forms decreased from trees to perennial herbs. Plant species exclusively pollinated during the night reached a peak during the rainy season (May to November) for trees, lianas and perennial herbs. The data as a whole show that the relative frequency of polyphily, oligophily, monophily and anemophily, and the time of pollination activity are influenced by community structure and plant species richness, and may change from season to season. © 2004 The Linnean Society of London.