Duperrea pavettifoliais a small tree typically growing in moist valleys in Southeast Asia including Xishuangbanna in the south of China. The wild populations are small and far distant from each other. Its flowers have a long exerted style with a large stigma, and show the typical features of secondary pollen presentation (SPP) type C (pollen deposition on the outer side of the stigma), according to Puff's classification. However, little is known about the species’ reproductive biology or the mechanisms involved in SPP.
Prof. Gao Jiangyun and his research team of Xishuangbanna Tropical Botanical Garden (XTBG) conducted an investigation in Xishuangbanna National Nature Reserve. They used ecological and microsatellite methods to study the reproductive biology of D. pavettifolia. Field work was carried out at the beginning of the rainy season, from May to June, in 2009, 2010, and 2011. Additional observations and experiments were also carried out on six individuals transplanted to XTBG.
They mainly addressed the four questions: (1) What is the mechanism of SPP in D. pavettifolia? (2) How does this species reduce the self-interference induced by the proximity of pollen and stigma? (3) What are the flower visitors and their influence on the reproduction of D. pavettifolia? (4) What is the mating system and genetic diversity of the wild population?
Their results indicated that protandry and the visitation of stingless bees reduced the amount of self-pollen on the still unreceptive stigma and self-incompatibility prevented fertilization by un-removed self-pollen.
The study entitled “Self-interference is reduced in a secondary pollen presentation species, Duperrea pavettifolia (Rubiaceae)” has been published in Flora - Morphology, Distribution, Functional Ecology of Plants， 207（12）: 895-902, http://dx.doi.org/10.1016/j.flora.2012.10.001
(a) Inflorescence of Duperrea pavettifolia; (b) stigmas with abundant pollen in functional male stage;
(c) furrows were obvious in functional female stage;
(d)–(g) flower visitors: (d) stingless bee; (e) fly; (f) butterfly (Papilio polytes); (g) hawkmoth (Macroglossum insipida).
(Images by Lin Hua)