Coadaptation entre rythmes de fructification et frugivorie en forêt tropicale humide du Gabon : mythe ou réalité ?

Fruiting patterns were studied for a year in lowland evergreen forest at Makokou, Gabon. Temporal patterns of fruiting were analysed according to vegetative life-form of the parent, morphological fruit type, seed dispersal mode and seed weight. In addition, fruiting cycles of 109 individuals of 13 species were monitored for two years. The results are summarized as follows : 1. Fruiting at Makokou is seasonal : fruiting peaks occur during the major rainy season and minor dry season, while the major dry season and minor rainy season are periods of fruit scarcity. A comparison with data from earlier years shows that there can be large inter-year variations in fruiting patterns. 2. There are some differences in the amplitude of fruiting seasonality depending on the parental life-form : as a group, medium-sized trees are the most strongly seasonal, emergent trees are less so. The monthly patterns of numbers individuals fruiting also differ between life-forms, as does the timing of fruiting peaks. 3. There is no clear seasonal difference in the amplitude of fruiting seasonality for different morphological types of fruits, or seed dispersal modes. Moreover, the yearly maxima in numbers of fruiting species are the same for anemochores, zoochores and autochores ; however, seasonal patterns differ depending on the fruit type (dehiscent vs indehiscent ; dull-colored fleshy fruit vs brightly-colored fleshy fruit). 4. There is no clear difference in amplitude of seasonality for fruits with different seed weights. 5. Analysis by species shows that regardless of dispersal mode, there is a complete gradient from species with strong seasonality, either annually uni-modal, or bi-modal, to those with weak seasonality and fruit production throughout most of the year. 6. Monitoring individual trees showed that among zoochorous species there can be annual, biennal or multiannual cycles, with regular, irregular or without obvious periodicity, and with fruiting synchrony or asynchrony among individuals of the same species. These results are compared to those reported for other tropical rainforests. Although we showed in a simultaneous study that there are broad suites of morphological fruit characters associated with broad categories of consumers (Gautier-Hion and al., 1985), the results presented here do not suggest an evo¬ lutionary influence of consumers on the timing of fruiting. While it is possible by selecting appropriate species subsets to suggest correlations demonstrating the influence of dispersal agents on phenology, it is likewise possible by choo¬ sing different subsets to formulate hypotheses about fruiting phenology in which coadaptation with dispersers does not play any role.Gautier-Hion Annie, Duplantier Jean-Marc, Emmons L., Feer F., Heckestweiler P., Moungazi A., Quris R., Sourd C. Coadaptation entre rythmes de fructification et frugivorie en forêt tropicale humide du Gabon : mythe ou réalité ?. In: Revue d'Écologie (La Terre et La Vie), tome 40, n°4, 1985. pp. 405-434