PLANT REPRODUCTIVE-BIOLOGY OF HERBACEOUS MONOCOTS IN A VENEZUELAN TROPICAL CLOUD FOREST

The reproductive biology of 29 herbaceous understory monocot species w as studied in a tropical cloud forest of northern coastal Venezuela (H enri Pittier National Park). Of the 23 plant species, 6 (26.1%) were s elf-incompatible and 17 (73.9%) self-compatible, the latter consisting of 12 (52.2%) fully self-compatible and 5 (21.7%) partially self-comp atible species. An analysis of sexual systems and temporal variation o f sex expression showed that of 29 monocot species, 14 (48.3 %) were h ermaphrodite and adichogamous, 14 (48.3%) monoecious and dichogamous, and one (3.4%) dioecious. The combination of monoecy and dichogamy pre vented autogamy in 11 (91.7%) of the 12 self-compatible and monoecious species; one (8.3%) was autogamous. Of all species, 24 (82.8%) were o bligate outbreeders, 2 (6.9%) spontaneously autogamous, and 3 (10.3%) partially autogamous. Ovule and flower abortion were not significantly different between the different groups. Pollen-ovule ratio was signif icantly different between monoecious and hermaphrodite species. The nu mber of pollen grains and ovules per flower and the pollen-ovule ratio were variable among various pollination types. The average pollen-ovu le ratio was higher in beetle-, dipteran-, and wind-pollinated species than in bee-, bird-, and bat-pollinated species. The first three poll ination types were restricted to monoecious species, and the second th ree groups were restricted to hermaphrodite species. Of 33 plant speci es investigated, 12 (36.4%) displayed vegetative reproduction. The rep roductive features of the understory monocot species are discussed in the context of life form, devices of cross-pollination, and geological history of the tropical cloud forest.