Pollination System of Mucuna thailandica (Fabaceae), a Species Endemic to Thailand

The pollination modes of plants vary among regions owing to faunal variations; however, knowledge of pollinators in tropical montane Asia is insufficient. Here, we elucidate the pollination system of Mucuna thailandica (Fabaceae), a plant endemic to the montane forest of Thailand. The genus Mucuna exhibits a distinctive pollination mechanism called “explosive opening″. The stamens and pistils of Mucuna flowers are covered by a pair of keel petals, and pollination is only possible when a flower is opened by a pollinator, which exposes stamens and pistil. In bagging experiments, unopened M. thailandica flowers did not bear fruit, indicating that an explosive opening was necessary for successful pollination. Automatic camera surveys showed that squirrels (Callosciurus finlaysonii/erythraeus complex and Dremomys rufigenis), masked palm civets (Paguma larvata), and northern treeshrews (Tupaia belangeri) opened the flowers explosively. Among them, the C. finlaysonii/erythraeus squirrels opened flowers most frequently, and three flowers bore fruits. Thus, C. finlaysonii/erythraeus squirrels may be effective pollinators of M. thailandica. Opening the flowers grants pollinators access to a large volume of nectar with a high sugar concentration as a reward. Our findings suggest that the role of nonflying mammals as pollinators in tropical Asian montane forests may be greater than previously thought.