稜果榕榕果生產及其揮發物之季節性變化

Abstract

榕屬植物 (Ficus spp.) 為泛熱帶及亞熱帶之關鍵物種，為台灣低海拔地區重要組成物種。本研究分為三部分探討稜果榕 (Ficus septica Burm. f.) 與共生生物之關係。第一部分為稜果榕榕果物候，探討4年2個月調查期間各年度之物候差異、雌雄株族群果候及葉候與氣象因子間的關係。葉候結果顯示台中地區稜果榕成熟葉量呈明顯季節變化，春、夏2季成熟葉量最高，冬季最低。調查期間雌株單株平均一年有2.89個果季、雄株有4.75個果季，雄株果季較雌株多約1.6倍。成熟葉量與榕果量呈顯著正相關，與平均氣溫、累積雨量及全天空日射量均呈顯著正相關。雌株榕果葉量比較雄株低，應為雌株對榕果投資與雄株不同。雌、雄株雌花期榕果幾乎全年不間斷，僅冬天雌株榕果生產較少，雌、雄株雌花期榕果量呈顯著正相關，榕果多能進入花間期且生產高峰多有重疊現象；雄株雄花期出現多能與雌花期榕果配合，反映樹德公園之稜果榕與授粉蜂有良好的共生關係。第二部份為稜果榕榕果揮發物，榕果揮發物被認為是吸引共生昆蟲的關鍵，且因榕果不同果期有不同的共生生物，因此各果期榕果揮發物有所差異。雌、雄株雌花期揮發物相似；雌、雄株花間期揮發物種類有所不同，雌株揮發物相對含量以主成分及非度量多維度排序法分析較群聚，然仍與雄株較難區分；雌、雄株成熟階段榕果揮發物有明顯區隔，表示榕果揮發物有性別分化。雌花期與花間期榕果揮發物未能清楚區隔，然明顯與成熟期及雄花期榕果區隔。與共生生物之關係：雌花期榕果揮發物能吸引授粉蜂，相似的揮發物可混淆授粉蜂判別榕果性別，分別進入榕果授粉或產卵；花間期榕果揮發物推測能幫助雌花期榕果吸引授粉蜂時，同時有著吸引寄生蜂的揮發物；成熟期榕果吸引昆蟲幫助其傳播，雄花期榕果為小蜂羽化之時，其揮發物與雌株不同，不吸引動物取食。第三部分為雌花期與花間期榕果揮發物之季節性變化，配合物候調查，發現2時期榕果揮發物相似程度恰相反。雌花期榕果生產高峰揮發物相似度提高可混淆授粉蜂，榕果生產低落的冬季揮發物較不相似，可能使授粉蜂較順利進入雌花期榕果。花間期榕果生產高峰揮發物相似度降低，雄株可能較吸引寄生蜂，此時榕果量足以被寄生而較不影響授粉蜂，冬季榕果生產較少揮發物相似度提高，可能使寄生蜂混淆，降低被寄生的機率。

Ficus spp. are the important compositions in lowland Taiwan and pantropical and subtropical “keystone species” This study was divided into three parts to discuss the mutualism of Ficus septica Burm. f. and its mutualistic fig-wasps. First was the phenology survey from November 2007 to February 2012, the purposes of the investigation were aimed on the fig phenology and leaf phenology with climate factors in any year. In leaf phenology, mature leaves showed seasonally, leaf quantity was spring and summer more than winter. Mature leaves were corresponded positively significant with average fig quantity, average temperature, precipitation and light radiation. During the period of phenology survey, figs growth complete had 2.89 times/year in female tree, 4.75 times/year in male tree. The production of fig/ leaf ratio was female tree less than male tree. May two genders had different investment in figs. Almost all the year had figs on trees, except on the production of winter. The fig production of two genders had positive significant. The production of figs had overlapped on genders, and genders female phase figs appeared simultaneously. Male phase and female phase fig could match each other, and growth to inter-floral phase, it illustrate the well mutualism of Ficus septica and its pollinator. Second part was use GC-MS to analysis different phase of fig volatiles. Fig volatile was considered to be the key of Ficus plants and pollinator mutualism. And the different fig phase volatiles impacted on different creature to symbiosis. The volatiles of genders female phase was similarity. In principal component analysis, the kind of inter-floral phase fig volatile compounds was different grouped, though the volatile of genders was a level of similarity. In mature stage fig, two genders volatile was pretty different, illustrated sex differential. Female phase and inter-floral phase odors was similarity, though the two phases had different on mature stage fig. Genders female phase odors similar could make pollinator confusion. Inter-floral fig odors like female phase may help to attract to pollinator, and it had some signal to attract non-pollinators. Mature phase attracted insect to be seed dispersers. Male phase not attracted to frugivores, ensure the pollinator not be disturbed. The final part was discussion the odors seasonal change of female phase and inter-floral phase with the background of fig phenology. In female phase, when fig produced higher, the genders fig odors emitted more similarity. In this situation, fig volatiles make pollinator confusion. When fig produced lower, the genders odors emitted less similarity. It may promote pollinators to male fig. In inter-floral phase, when fig produced higher, the fig odors emitted less similarity. It occurred in summer, figs had enough pollinate site to be pollinated by non-pollinators. When fig produced lower, the fig odors emitted more similarity. It occurred in winter, high similarity may make confusion to non-pollinator. Moreover, it may the mechanism of Ficus septica protecting it pollinator crowd.