Feral African Bees Augment Neotropical Coffee Yield

No previous work describes natural history of coffee pollination in semi-natural habitats, but without intrusion of hived bee colonies. In Panama highlands having feral honeybees since 1985, the fruit and seed set of Coffea arabica was monitored during 1997 in bagged and open flowers on 558 shrubs in 11 transects within a range of 13 km, at elevations of 13001600 m. Caturra varieties were studied either next to old forest or in more open, mosaic habitats, while Catimor, an interspecific hybrid grown in “sun” plantations, was studied at a single site. Four honeybee hives were kept in the Catimor plantation. Bees, the common visitors, were most abundant on flowers near old forest. Significant native visitors included Centris festiva, Bombus pullatus, B. volucelloides, Trigona fulviventris, T. nigerrima, and T. (Tetragonisca) angustula, but Apis mellifera scutellata made >95% of all flower visits in all areas. Visitation was not accurately measured by number of bees per flowering shrub, compared to bees per flower. Neither was the value of open pollination adequately gauged within a single branch with bagged and open flowers, compared to bagged and open branches on the same shrub. Flowers of C. arabica were found to be distylous, with 11 individual shrubs having short-styled flowers. Their fruit set and seed set, both in bagged and open flowers, was no different from the more common long-styled plants. Caturra and Catimor showed over 25% fruit retention increases from pollinating visits by bees. For the former, seeds were over 25% heavier and developed faster from open pollination. Yield benefit from open pollination, chiefly by feral African bees, was 56%. Older plants, however, did not respond by increasing fruit set, nor did Catimor produce heavier fruit when pollinated by bees.