Reproductive ecology of white cacao (Theobroma bicolor Humb. & Bonpl.) in Ecuador, western Amazonia: floral visitors and the impact of fungus and mistletoe on fruit production

Abstract

Theobroma bicolor is widely distributed in the Neotropics with great potential for economic use. However, very little is available in literature about its pollinators and reproductive ecology in comparison to what is available about its economically more important relative T. cacao. We studied aspects of the floral biology, reproductive phenology and biotic restrictions to the reproduction of the species. We measured, observed and monitored flowers and described their morphology, breeding system, receptivity times of the stigma and peaks of flower and fruit production. During 20 consecutive days, we collected floral visitors of 135 ± 45 flowers per day. We also calculated the damage in fruit production generated by the mistletoe (Oryctanthus cf. alveolatus) and the fungus (Moniliophthora roreri). We found that flower stigma was more receptive between 6:00–10:00 and flowers last up to three days on the tree, which is less time than what has been reported elsewhere. We collected 211 insects from 68 different morphotypes, but five of these represented 49.8% of the total; specimens of Ceratopogonidae, Chironimidae and Sciaridae were the most abundant and could be pollinators of the species. The flowering of T. bicolor showed a positive correlation (r > 0.75) with the months with higher temperature and solar radiation. We recorded an average per tree of 7 ± 5 fruits. We found a drastic loss of 84% of fruits in the plants infested by the mistletoe O. cf. alveolatus and of 29% when infested by the fungus M. roreri. The results of this study serve as a basis to generate local management practices.