Floral reproductive biology of Xylopia championii Hook. F. and Thoms. (Annonaceae)
2004
Ratnayake, R.M.C.S.(The Univ. of Hong Kong, Pokfulam Road, Hong Kong (China). Dept. of Ecology and Biodiversity)E-mail:[email protected] | Gunatilleke, L.A.U.N | Wijesundara, D.S.A. | Saunders, B.M.K.
The Annonaceae exhibits a great diversity of floral structures with a correspondingly broad range of pollination systems. Most previous research into the reproductive biology of the family has been focused on neotropical species. The present research describes beetle pollination in the rare Sri Lankan endemic, Xylopia championii Hook. f. and Thoms. The flowers are hermaphroditic, with three large outer petals and three smaller inner petals; the inner petals form an enclosed chamber over the reproductive organs. Penological research shows that the flowers are reproductively functional for a 2-day period. The flowers are photogynous , with the pistillate phase beginning around 15:00 hrs on day 1; this phase continues until 6:00 hrs on day 2, when stigmatic receptivity ceases. There is then an interim period until the flower enters its staminate phase (with anther dehiscence) at around 14:00 hrs on day 2; this period continues until early the next morning. Thermogenesis is evident during both reproductive phases. The main floral visitors are small Endaeus weevils (Coleoptera: Curculionidae), which are attracted by 'fruity' scents emitted when the flowers are receptive. The weevils were observed to have pollen of X. championii adhering to their bodies, indicating that they are effective pollinators. Chemical analysis of the volatile compounds in the odours reveal the presence of several compounds previously reported to act as sex pheromones in related Coleoptera groups. Controlled pollination experiments conducted in the field confirm that X. championii is self-incompatible and xenogamous.
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