Diversity, Distribution and Behavior of Bee Pollinators (Hymenoptera: Apoidea) Effect the Amount of Pollen Grains on Physic Nut (Jatropha curcas L.) in Thailand

Abstract

A survey was made on the diversity and distribution of bee pollinators visiting physic nut (Jatropha curcas L.) flowers, and on flower sex variation, covering sample plantation sites in 20 provinces in Thailand from April to August, 2009. Sixty-one species of bee in the superfamily Apoidea were found visiting flowers of the physic nut. The Indian honey bee (Apis cerana indica F.), in the social bees, had the most widespread distribution, followed by the dwarf honey bee (A. florea F.), the giant honey bee (A. dorsata F.), and a stingless bee (Tetragonula pagdeni Schwarz). Bee pollinators preferred female to male flowers. Physic nut flowers in all locations were mainly pollinated by bees. Physic nut plants were found to be androgynous, polygamous and/or gynoecious. A single gynoecious plant, producing only female flowers, was observed, which was the first such plant to be reported in Thailand. In the wet season, the flower sex ratio among the 5 regions was significantly different. The ratios in the south, north and east regions (1 female per 10.00±1.38, 10.33±3.76 and 10.50±1.10 male flowers, respectively) were higher than those in the central and northeast regions (1 female per 13.67±7.80 and 15.00±5.51 male flowers). The polygamous plants in Suphan Buri province exceptionally showed 9 females: 23 males: 7 perfect flowers in non-toxic variety.