Biodiversity Science ›› 2011, Vol. 19 ›› Issue (1): 24-33.doi: 10.3724/SP.J.1003.2011.10167

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Floral syndrome and secondary pollen presentation in Codonopsis clem-atidea (Campanulaceae)

Li Wang1, 2, Dunyan Tan1*   

  1. 1Xinjiang Key Laboratory of Grassland Resources and Ecology & Ministry of Education Key Laboratory for Western Arid Region Grassland Resource and Ecology, College of Grassland and Environment Sciences, Xinjiang Agricultural University, Urümqi 830052

    2Qinggeda Lake Nature Reserve Administration Station, Xinjiang Production and Construction Corps Construction of the Sixth Agricultural Division, Wujiaqu, Xinjiang 831300
  • Received:2010-06-30 Revised:2010-10-03 Online:2011-04-01
  • Dunyan Tan E-mail:tandunyan@163.com

Secondary pollen presentation has been described as a reproductive strategy that enhances the ef-ficiency and accuracy of pollen exportation and pollen reception, thereby promoting outcrossing. Codonopsis clematidea is characterized by secondary pollen presentation. The objective of this research is to study the floral syndrome and the procedure of secondary pollen presentation of this species, with special reference to the adaptive significance of these features based on the field observations, hand-pollination experiments and indoor microscopic observations. The results showed that the blue campanulate pendulous corolla and black and yellow nectary of C. clematidea not only protect the androecium and gynoecium from rain damage and prevent rain water from diluting the nectar and removal of pollen by wind, but they also attract more pollina-tors and extend the duration of pollen viability and stigma receptivity. The secondary pollen presentation of this species is sub-terminal stylar presenters and belongs to the deposition mechanism. This character limits the amount of pollen removed by the pollinators and prolongs pollen presentation, thus attracting more pollinators and thereby increasing male fitness. The protandry and the change of the spatial position of male and female organs during the flowering stage of C. clematidea not only avoid interference between male and fe-male functions, but also create a passageway for pollinators to forage for nectar and pollen and for stigmas to receive outcross pollen. Bombus silvarum, B. paradoxus and Dolichovespula sylvestris are the effective pol-linators in the generalist pollination system of this species. Other floral characteristics of this species, such as long flowering duration (approximately 6 d) per flower, overlap of the peak of insects visitation in the male and female phases with the period of highest pollen viability and the optimal stigma receptivity of pollen, lots of nectar that contains a higher sugar concentration and a long period of nectar secretion during the flowering stage, etc, enhance visitation frequencies and the chances of successful pollination. Therefore, these traits help improve pollination efficiency and promote outcrossing. The special floral syndrome and the mechanism of secondary pollen presentation are significant in improving pollination efficiency and promoting the repro-ductive success of Codonopsis clematidea by outcrossing under changeable weather conditions in Tianshan Mountains.

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