Phenology and Floral Biology of Gustavia superba (Lecythidaceae) in Central Panama

Abstract

Leaf fall, leaf production, flower and fruit production, and floral biology of Gustavia superba (Kunth) Berg were studied for a year in the tropical moist forest of central Panama. Although leaves fall throughout the year, peak fall occurs in the first month of the wet season. Leaf production on any branch is possible throughout the year, but within the population studied two pronounced peaks were observed, one in the late wet-early dry season and the other after the first rains of the wet season. Flowering began about one month after the rains ceased and continued throughout the dry season into the first month of the following wet season. Fruits reached maturity at the end of the dry season and into the early wet season. The severity of the dry season of 1974-1975 may have altered the normal flowering pattern and reduced fruit production in this species. Observations revealed that the flowers are diurnal, without odor anid nectar, and are visited by bees for their pollen. A limited number of crosses suggest that this species is self-incompatible. SEVERAL PAPERS IN RECENT YEARS have emphasized the peak in flowering of trees in the seasonally dry forests of Central America in the dry season (Fournier and Salas 1966, Janzen 1967, Croat 1969, Frankie et al. 1974). Not only do more tree species bloom during this time of the year but those that do bloom tend to have larger, more spectacular flowers. In central Panama the large, bright-yellow flowers of Tabebuia guayacan (Seem.) Hemsl., T. ochracea (Cham.) Standl. subsp. neochrysantha (A. Gentry), A. Gen,try, Cespedesia macrophylla Seem., and Cochlospermum vitifolium (Willd.) Spreng., the golden-yellow flowers of Cassia moschata Benth., the duller yellow flowers olf Byrsonima crassifolia (L.) H.B.K., the pink flowers of Tazbebiaz rosea (Bertol.) DC., and the red ones of several species of Erythfina are among the more spectacular indicators of the dry season. The number of species with maturing fruit is also greater during the dry season (Janzen 1967, Croat 1969, Smythe 1970, Frankie et al. 1974). Smythe (1970) has demonstrated a pronounced peak of large animal-dispersed seeds (over 1.5 cm in greatest diameter) at the end of the dry season into the early wet season. In addition to flowering and fruiting, certain vegetative phenomena coincide with the dry season in the seasonal tropical forests of Central America. Frankie et al. (1974) and Daubenmire (1972) have shown a distinct dry-season peak in leaf fall for a number of species of trees studied in Guanacaste Province, Costa Rica. Production of new leaves at the beginning of the dry season has been demonstrated in several species by Rockwood (1975, table 8) and toward the end of the dry season and into the rainy season by Daubenmire (1972) and Frankie et al. (1974). Even though certain phenological patterns predominate in moist tropical forest with seasonal rainfall, there are, nonetheless, many deviations from these patterns. For example, most deciduous tree species lose their leaves in the dry season, but some species like Jacquinia pungens A. Gray (Janzen 1970) and Cordia alliodora (Ruiz & Pavon) Cham. (T. Croat, pers. colmm.) lose their leaves in the wet season. The large animal-dispersed seeds of Spondias mombin L. and S. radlkoferi J. Donn. Sm. ripen and fall in the midto late-wet season in contrast to the peak for this fruit type at the end of the dry season and early wet season (Smythe 1970, Croat 1974). Because of these and other exceptions to general phenological patterns, phenological studies of individual species of seasonal tropical forest are needed.