Biodiv Sci ›› 2012, Vol. 20 ›› Issue (3): 376-385.  DOI: 10.3724/SP.J.1003.2012.10034

Special Issue: 传粉生物学:理论探讨与初步实践 传粉生物学

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Adaptive significance of mass-flowering in Hedychium coccineum (Zingiberaceae)

Jiangyun Gao1,*(), Chunling Sheng1,2, Shuxia Yang1,2   

  1. 1 Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303
    2 Graduate University of the Chinese Academy of Sciences, Beijing 100049
  • Received:2012-01-30 Accepted:2012-04-25 Online:2012-05-20 Published:2012-05-09
  • Contact: Jiangyun Gao


Hermaphroditic plants that simultaneously display multiple flowers may attract more pollinators and create more chances for mating. However, this may also lead to geitonogamy, which may have major impacts on evolution of sex allocation, floral characteristics, and dioecy. To explore adaptive significance of mass-flowering in Hedychium coccineum, we conducted studies on pollination biology of H. coccineum, via hand-pollination and manipulated experiments, pollinator observation, and investigations on population density and natural fruit sets. Overall, inflorescences of H. coccineum were composed of terminal spikes containing 57.33 ± 1.68 (n = 30) cincinnus, and each cincinnus possessed 3.8 ± 0.15 (n = 30) flowers. Flowers in each cincinnus opened in turn, and the same round flowers among each cincinnus within inflorescences opened in successive synchronous cycles. This provided a spike that kept a mass of flowers blooming simultaneously throughout the flowering period. H. coccineum displayed a large floral display at the inflorescence level. Additionally, H. coccineum was self-compatible, and spontaneous self-pollination did not occur. Fruit production of H. coccineum in natural populations was severely pollinator-limited. Meanwhile, H. coccineum was also resource-limited in fruit production. Three butterflies, Papilio memnon, Dercas lycorias, and Appias indra aristoxemus were effective pollinators of H. coccineum. Visiting frequencies of these butterfly species to three inflorescences with different floral display size were obviously different and visitation frequencies increased as the inflorescence increased in floral display size. Pollen grains and ovules of H. coccineum varied significantly among flowers of different rounds in the cincinnus. Ovule production decreased significantly from the first to the fourth round, but pollen grains increased significantly from the first round to the third round. The decrease in ovules and resource limitation in fruit production indicated that mass-flowering in H. coccineum was not for increasing fruit production. The increase in pollen grains from the first round to the third round benefits pollen export and increases male fitness.

Key words: Hedychium, floral display, floral longevity, flowering pattern, geitonogamy, inflorescence structure, sex allocation