台灣產玉葉金花生殖生物學與族群遺傳之研究

Abstract

本研究在研究一個台灣獨特的例子-玉葉金花（ Mussaenda pubescens），其在台灣北部和 東北部的族群中，缺乏明顯的萼片來吸引傳粉者，但是結果率仍然很高。我們希望瞭解它是 如何克服這個先天的劣勢。玉葉金花是台灣低海拔中常見的植物之一，它是一個雌雄異株的 植物。玉葉金花常可以見到花萼其中的一個裂片尖端膨大成一個外形類似葉子、但顏色為白 色或紅色的構造，稱為葉狀萼片（calycophylls, 或floral semaphylls）。而玉葉金花名稱的由 來，即源於它的花序中黃色的花瓣和白色的葉狀萼片而來。這些葉狀萼片不管在細胞形狀或 細胞排列上，都與正常的花瓣類似，加上有著顯著的顏色，一般皆認為這些葉狀萼片在功能 上與花瓣無異，而與吸引有效傳粉者有關。在前人與我們的觀察中發現，在台灣北部至新竹， 及東北部以至南澳的玉葉金花族群中，都沒有膨大的花萼構造。我們選擇了台北縣樹梅坪， 苗栗三義，和屏東南仁山的三個族群進行研究。其中只有樹梅坪的族群是沒有膨大的花萼構 造。我們針對這些族群進行傳粉者，蜜腺分泌，花粉萌發率，結果率的觀察，以及利用SEM 進行花器細部觀察。另外我們也同時利用分子工具進行譜系分析。我們所選用的是核內ITS 的序列。藉由對玉葉金花的生殖生物學的研究，我們想探討東北部的族群中，是否有新的傳 粉者，或者有其他的因素能幫它們克服失去膨大花萼的劣勢。本計畫原本為期兩年，但因經 費僅支持一年，故本報告實為不完整的先期報告。

Floral display is critical to attract pollinators for animal-pollinated plants. Loss of visual signal of flowers may well decrease the reproductive success, and eventually lead to extinction of such plant. We would like to investigate a unique case in Taiwan’s Mussaenda pubescens, in which some populations may have survived the loss of showy floral signal. Mussaenda pubescens Ait., a member of Rubiaceae, has a distinct enlarged calyx-lobe which is generally thought to attract pollinators like butterflies. The high-contrast visual signals have been shown to be essential for high fruit sets in another Mussaenda species, M. parviflora. Based on our survey, we found many of the M. pubescens populations in northeastern Taiwan lack the showy semaphyll. The preliminary observation showed that these individuals are able to bear fruits, suggesting that cross-pollination still occurs and they somehow overcame the deficiency in pollinator attractants. We performed a survey for floral morphology, nectar secretion pattern, and SEM observation among the populations with and without enlarged semaphylls. We also performed a phylogenetic analysis using nrITS sequences among three study sites of M. pubescens. This will help to understand the systematic identities with different semaphyll types in M. pubescens,. The original plan is to have a two-year experiment for long-term observation. Since this grant is funded only for one year. We have preliminary data shown here.