Flowering Phenology and Pollination Systems
Diversity in the Seasonal Dry Forest
Gordon W. Frankie, William A. Haber, S. Bradleigh Vinson,
Kamaljit S. Bawa, Peter S. Ronchi, and Nelson Zamora
When comparing Neotropical life zones, one of the first generalizations to emerge is that seasonal dry forests have lower species diversity than wetter or more aseasonal life zones (Janzen 1983; Bullock et al. 1995). This pattern is easily recognized. The species-level count, however, is only one aspect of a much larger picture of biodiversity. Noss and Cooperrider (1994: 5) provide a useful definition of biodiversity that is relevant to this discussion: “Biodiversity is the variety of life and its processes. It includes the variety of living organisms, the genetic differences among them, the communities and ecosystems in which they occur, and the ecological and evolutionary processes that keep them functioning, yet ever changing and adapting. ”
In this chapter we focus on selected processes of plant reproduction in the highly seasonal dry forest of Costa Rica and their evolutionary implications. The chapter has three goals. First, we document the diversity of flowering phenological patterns and pollination systems in the dry forest. Second, we compare the diversity with that of other tropical forests. Third, we explore the significance of this diversity and how it might be affected by environmental disturbances caused by humans.
Community-level periodicity patterns of leaf fall, leaf flushing, flowering, and fruiting were determined for Costa Rican dry forest trees and shrubs from 1969 to 1970 and from 1971 to 1973. Patterns were found to be closely associated with the highly seasonal dry and wet periods (Frankie et al. 1974; Opler et al. 1975, 1976, 1980). The major seasons are the long dry period from early November to early May and the wet period from late May to early November, with a brief, but variable, dry spell from July to August (Frankie et al. 1974). The forestwide patterns, as well as