Study On The Reproductive Ecology Of Zingiberaceae

The Zingiberaceae is a large family of animal-pollinated tropical monocotyledons with approximate 1,500 species in 50 genera. Members of this family display a broad range of pollination and breeding systems. Ginger plants are considered to be an ideal plant group for studying the evolution of pollination and breeding system of flowering plant. In this study, 4 ginger species in 3 genera with different floral characteristics are selected for studying the reproductive ecology with special focus on floral longevity.Curcumorpha longiflora (Wallich) A. S. Rao & D. M. Verma is a perennial chasmophyte ginger that usually grows in crevices of calcareous rocks and forms patches on the understory of limestone monsoon rainforests. The pollination ecology of C. longiflora was studied by monitoring phenology and flowering behavior, observing pollinator activity, and the quantity and quality of pollination services. We also investigated the germination of pollen grains and growth of pollen tubes after different pollination treatments to detect its breeding system. Based on the results: (1) for the first time in Zingiberaceae a new protandrous mechanism was found with a two-day flowering to avoid autogamy in this species; (2) under field conditions, all individuals of C. longiflora usually produced only one flower every other day to keep geitonogamy to a minimum; (3) germination of pollen grains and growth rates of pollen tubes under different pollination treatments were the same 4 h later after pollination, suggesting that C. longiflora is completely self-compatible; (4) among the limited visitors, Bombus sp. and Apis florae were effective pollinators, but they were active at different times and at different stages of the flower, probably receiving different rewards.Rhynchanthus beesianus W. W. Smith is an epiphytic tropical ginger with a very conspicuous floral display, but almost no fruit set under field conditions. The reproductive ecology encompassing phenology, floral biology, and pollination and breeding systems was investigated in an evergreen broadleaved forest in Yunnan Province, Southwest China. The flowers possess a typical bird pollination syndrome, but no effective pollinators were observed during 138 h of observation. Female Black-breasted Sunbird (Aethopyga saturata) and bumblebees visited R. beesianus regularly, but they all played roles as nectar robbers. No fruit was found in the bagging treatment, and fruit set following manual self-pollination (57.55±4.08%) was comparable with cross-pollination (64.32±4.42%), suggesting that R. beesianus is self-compatible but spontaneous self-pollination in this species does not occur. R. beesianus was dependent on animals for fertilization and suffered a serious pollinator-limitation. Bird extinctions as a result of habitat fragmentation may lead to a decline of pollination and fruit set in R. beesianus. The floral longevity of R. beesianus is 2.5 days, but its showy red bracts last for 4-5 days as attractant to pollinators.Hedychium coccineum Smith is a self-compatible ginger with very conspicuous floral display at the inflorescence level, but fruit set in natural population suffered both serious pollen-limitation and resource-limitation. Butterflies are main pollinators of H. coccineum. In our observation, the visit frequency of 3 butterflies to H. coccineum increased greatly following the increase of total flowers on an inflorescence. The floral longevity of H. coccineum is 2 days. A cincinnus contains 3-4 flowers, and flowers bloom in turn. In cincinnus, the pollen grains of different flowers increase significantly in ture, but ovules numbers decline significantly in ture. Large floral display at the inflorescence level is advantageous both to attract pollinators and increase male fittness in H. coccineum. The two varieties of Hedychium villosum Wallich in Roxburgh, diploidy var. tenuiflorum and tetraploidy var. villosum, are morphologically different in palnt size, floral size and numbers of pollen grains, ovules and cincinnus. There is no any difference in floral design between two varieties. Tetraploidy var. villosum is much widespread than diploidy var. tenuiflorum geographically and ecologically, and the reproductive isolation occur between two varieties through flowering season. Diploidy var. tenuiflorum is post-zygotic self-incompatible and tetraploidy var. villosum is completely self-compatible. Both butterflies and hawkmothes are effective pollinators of two varieties, but strong differentiation in butterfly and hawkmoth species occurred to two varieties. The floral longevity of var. tenuiflorum and var. villosum are 4 days and 5 days respectively. Diploidy var. tenuiflorum shows stronger clonal ability than tetraploidy var. villosum does, and the fruit-set of var. tenuiflorum is significantly negative relative to clone size in natural population. The breakdown of self-incompatibility associated with polyploidy in H. villosum lead to changes in flowering time, pollinators, sexual versus asexual reproduction between diploidy var. tenuiflorum and tetraploidy var. villosum, which may cause tetraploidy var. villosum can explore new habitation and widespread. Polyploidy may play an very important role in distribution of Hedychium specieas from tropical area to high elevation area. Hedychium J. Konig is the only large genera distributed from tropical area to high elevation area in Zingiberaceae. Members of this genera vary greatly in floral longevity. The floral longevity of Hedychium villosum var. villosum is 5 days which is much longer than other sympatric gingers. We reduced the functional floral longevity for female function by clipping stigmas to test whether the long flowering duration of var. villosum increase female fitness by measure the fruit-set of different treatments.The results show that fruit-set incresed following the increse of female functional duration. Flowers with reduced functional floral longevity to 1 day had only 1.85±1.59% fruit-set which is significantly lower than 20.96±4.13% fruit-set of control flowers with natural longevity. Meanwhile, the mean pollen grains remiand on anthers of flowers 1 day after anthesis has no significant difference with the mean pollen grains of unopened flowers, but the mean pollen grains remiand on anthers of flowers 2, 3, 4 days after anthesis are all significantlly lower than the mean pollen grains of unopened flowers. These results indicate that the long floral longevity is advantageous both to male and female fitness in var. villosum. Long floral longevity may contribute to exploring new habitation and spreading toward high elevation area in tetraploidy var. villosum.Floral longivity not only plays a key role in form of diversity and evolution of pollination and breeding system of ginger famlily, but also plays an very important role in exploring new habitation and spreading toward high elevation area from tropical area in ginger famlily.