and Fruit Set of Six Neotropical Shrubs1

Abstract

Temporal patterns of flower production and the level of fruit set were determined for 20 individuals each of six shrub species (four families) in a semi-deciduous lowland forest in Panama. The species were: Hybanthus prunifolius, Turnera panamensis, Rinorea sylvatica, Psychotria horizontalis, Erythrina costaricensis var. panamensis, and Pentagonia macrophylla. There were two objectives of the study: 1) to compare among species the relation between the individual's flowering pattern and the population's flowering synchrony; and 2) to compare within species the relative influence of the individual's and the population's flowering phenology on the individual's fruit set. The six species differed in number of flowers per individual (mean values for species ranged from 98-2995), how long the individual produced flowers (mean values ranged from 3.5-59.0 days), and synchrony of the individual with its conspecifics (mean values ranged from 0.48-0.95, where value of 1.0 = perfect synchrony). Among the six species, population synchrony increased as the mean duration of an individual's flowering decreased. Population synchrony of the first day, peak (median) day, and the entire flowering period were highly correlated. When comparing individuals within each species, the individual's flower number was the best predictor of fruit set. Neither the individual's length of flower production nor its synchrony with conspecifics added significantly in explaining the variance in fruit set. A regression including the individual's number of flowers, length of flower production, and synchrony with conspecifics as independent variables and the proportion fruit set (and its arcsin transformation) as the dependent variable yielded no significant regressions. The consequences of these widely varying phenological patterns are discussed. Comparisons are made with the temporal patterns observed in other tropical forests. OUR