Yu Zhang1, Yuan-Yuan Li2, Miaomiao Wang3, Jia Liu3, Fanqiang Luo4, Yung-I Lee5,6. 1. Beijing Floriculture Engineering Technology Research Centre, Beijing Laboratory of Urban and Rural Ecological Environment, Beijing Botanical Garden, Beijing, 100093, China. bjyzhang@hotmail.com. 2. College of Plant Protection/Beijing Key Laboratory of Seed Disease Testing and Control, China Agricultural University, Beijing, 100193, China. 3. Beijing Floriculture Engineering Technology Research Centre, Beijing Laboratory of Urban and Rural Ecological Environment, Beijing Botanical Garden, Beijing, 100093, China. 4. Administration Bureau of Hainan Diaoluoshan National Nature Reserve, Diaoluoshan Forestry Bureau of Hainan Province, Lingshui County, 572433, Hainan, China. 5. Biology Department, National Museum of Natural Science, 40453, Taichung, Taiwan. leeyungi@hotmail.com. 6. Department of Life Sciences, National Chung Hsing University, 40227, Taichung, Taiwan. leeyungi@hotmail.com.
Abstract
BACKGROUND: Seed dispersal allows plants to colonize new habitats that has an significant influence on plant distribution and population dynamics. Orchids produce numerous tiny seeds without endosperm, which are considered to be mainly wind-dispersed. Here, we report avian seed dispersal for an early diverging orchid species, Neuwiedia singapureana, which produces fleshy fruits with hard seed coats in the understory of tropical forests. RESULTS: Neuwiedia singapureana produced fleshy fruits that turned red in autumn, and birds were confirmed to be the primary seed dispersers. As compared to its sister species, N. veratrifolia with dehiscent capsular fruits, embryos of N. singapureana were larger and enclosed by thickened and lignified seed coats. After passing through the digestive tracts of birds, the seeds still stayed alive, and the walls of seed coat contained several cracks. The germination percentage increased significantly for digested seeds as compared with seeds from intact fruits. CONCLUSION: The thickened and lignified seed coat may protect seeds as they passed through the digestive tracts of birds. Taken together with a recent report of insect-mediated seed dispersal system in the subfamily Apostasioideae, the animal-mediated seed dispersal may be an adaptive mechanism promoting the success of colonization in dark understory habitats.
BACKGROUND: Seed dispersal allows plants to colonize new habitats that has an significant influence on plant distribution and population dynamics. Orchids produce numerous tiny seeds without endosperm, which are considered to be mainly wind-dispersed. Here, we report avian seed dispersal for an early diverging orchid species, Neuwiedia singapureana, which produces fleshy fruits with hard seed coats in the understory of tropical forests. RESULTS:Neuwiedia singapureana produced fleshy fruits that turned red in autumn, and birds were confirmed to be the primary seed dispersers. As compared to its sister species, N. veratrifolia with dehiscent capsular fruits, embryos of N. singapureana were larger and enclosed by thickened and lignified seed coats. After passing through the digestive tracts of birds, the seeds still stayed alive, and the walls of seed coat contained several cracks. The germination percentage increased significantly for digested seeds as compared with seeds from intact fruits. CONCLUSION: The thickened and lignified seed coat may protect seeds as they passed through the digestive tracts of birds. Taken together with a recent report of insect-mediated seed dispersal system in the subfamily Apostasioideae, the animal-mediated seed dispersal may be an adaptive mechanism promoting the success of colonization in dark understory habitats.