Pollination of Schisandra henryi (Schisandraceae) by female, pollen-eating Megommata species (Cecidomyiidae, Diptera) in south-central China.
OBJECTIVE
The mutualistic interaction between insects and flowers is considered to be a major factor in the early evolution of flowering plants. The Schisandraceae were, until now, the only family in the ANITA group lacking information on pollination biology in natural ecosystems. Thus, the objective of this research was to document the pollination biology and breeding system of Schisandra henryi.


METHODS
Field observations were conducted in three populations of S. henryi and the floral phenology, floral characters and insect activities were recorded. Floral fragrances were sampled in the field and analysed using TCT-GC-MS. Floral thermogenesis was measured with a TR-71U Thermo Recorder. Pollen loads and location of pollen grains on insect bodies (including the gut) were checked with a scanning electron microscope and under a light microscope.


RESULTS
Schisandra henryi is strictly dioecious. Male flowers are similar to female flowers in colour, shape, and size, but more abundant than female flowers. The distance between tepals and the androecium or gynoecium is narrow. Neither male nor female flowers are fragrant or thermogenic. Schisandra henryi is pollinated only by adult female Megommata sp. (Cecidomyiidae, Diptera) that eat the pollen grains as extra nutrition for ovary maturation and ovipositing. Both male and female flowers attract the pollinators using similar visual cues and thus the female flowers use deceit as they offer no food.


CONCLUSIONS
Schisandra henryi exhibits a specialized pollination system, which differs from the generalized pollination system documented in other ANITA members. Pollen is the sole food resource for Megommata sp. and the female flowers of S. henryi attract pollinators by deceit. This is the first report of predacious gall midges utilizing pollen grains as a food source. The lack of floral thermogenesis and floral odours further enforces the visual cues by reducing attractants for other potential pollinators.
Yuan
Liang-Chen
LC
State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Xiangshan, Beijing 100093, People's Republic of China.
Luo
Yi-Bo
YB
Thien
Leonard B
LB
Fan
Jian-Hua
JH
Xu
Huan-Li
HL
Chen
Zhi-Duan
ZD
D000818:Animals; D001947:Breeding; D002681:China; D004175:Diptera / Q000502:physiology* / Q000648:ultrastructure; D005247:Feeding Behavior; D005260:Female; D035264:Flowers / Q000033:anatomy & histology / Q000254:growth & development; D008855:Microscopy, Electron, Scanning; D011058:Pollen / Q000254:growth & development / Q000502:physiology*; D032141:Schisandra / Q000502:physiology*; D014919:Wind