Phenological diversity in tropical forests

One of the most intriguing and complex characteristics of reproductive phen ology in tropical forests is high diversity within and among forests. To un derstand such diversity, Newstrom et al. provided a systematic framework fo r the classification of tropical flowering phenology. They adopted frequenc y and regularity as criteria with priority, and classified plants in La Sel va, Costa Rica, where most plants reproduced more than once a year irregula rly. Many other studies have demonstrated annual cycles corresponding to ra infall patterns at the community level in Neotropical forests, including La Selva. On the other hand, supraannual flowering synchronized among various plant species, called general flowering, is known from aseasonal lowland d ipterocarp forests in Southeast Asia. Within both forests, a wide spectrum of flowering patterns is found. This range of patterns suggests the great p otential of tropical phenological studies to explore the selective pressure s on phenology. Various abiotic and biotic factors can be selective agents. The shared pollinators hypothesis suggests that plant species sharing poll inators segregate flowering temporarily to minimize interspecific overlap i n flowering times and thus minimize ineffective pollination or competition for pollinators, indicating strong phylogenetic constraints in timing and v ariation of flowering. Comparison of phenology within and among forests may help our understanding of phenological diversity. Attempts are now being m ade to develop a common language to communicate concepts and render interpr etations of data more compatible among investigators and to create a networ k to promote comparative studies.