臺灣白肉榕的物候

Abstract

物候生物學是植物科學中重要的基礎資訊，榕屬植物和榕果小蜂間的互動使植物呈現出獨特的物候關係，而此研究的目的是瞭解台灣白肉榕（Ficus virgata Reinw)的生長與繁殖。白肉榕是台灣常見榕屬植物之一，為雌雄異株的半附生灌木或喬木，源自於熱帶地區，北以日本南端島嶼為界。本研究在台北市區有14棵樣樹，東北角海岸的鼻頭角則有11棵，從2010年4月至2012年3月歷時2年，每週記錄樣枝上葉片與榕果生長情形，並統計分析不同性別、地區的生長差異。 白肉榕為常綠植物，葉片壽命約1年，新葉在老葉脫落之前萌發，使樹能維持穩定的總葉量；榕果和葉片生長情形有些許差異，榕果每年有兩次主要生長期：一次發生於早春至早夏，另一次則是晚夏至秋季。台北市因為都市熱島效應影響微氣候，平均溫度較高，但白肉榕的生長模式與台灣其他榕屬植物並沒有太大差異，顯示白肉榕在台灣的生長十分穩定；相對來說，鼻頭角的氣候較為濕冷，因而使植物物候與台北市有所差異：台北市的族群以母樹葉量、果量和花期均勻度值較高；鼻頭角則剛好相反，以公樹葉量、果量花期均勻值較高。 雌雄異株的植物為了適應環境，雌雄株有不同的生殖策略。白肉榕的雄樹族群幾乎全年皆有連續果期產生，以維持小蜂族群；雌樹則無明顯連續的果期，僅在溫暖季節長果，幫助種子發育並提供更多機會吸引食果動物取食、散播，此外，因應種子發育所需提供大量的養分，雌榕果的體積、重量皆高於雄榕果；表現出雌雄異株植物在生長、繁殖中，有不同的資源投資策略。 這是白肉榕的首次研究成果，展現臺灣雌雄異株榕屬植物的特有物候模式。也希望這樣的研究，可以幫助榕屬植物的保育，並提供更多資料幫助都市化對物候與生物多樣性影響的研究。

Phenology is important basic information for understanding the mutualistic interactions between Ficus plants (Moraceae) and fig wasps (Agaonidae). The purpose of this study is to investigate the growth and reproduction pattern of Ficus virgata at northen Taiwan. Ficus virgata is one of the common fig tree species in Taiwan which is a dioecious hemiepiphytic shrub or tree. It mainly distributed in tropical area and the its northern limit is Ryukyu Islands (Japan) and the North of Taiwan Island. In this study, 14 trees at Taipei city and 11 trees at Bitou cape ( on the northeast coast) were regularly surveyed by every 1-3 week from April 2010 to March 2012. Besides establishing the first baseline data on description of phenology and fig growth patterns of this Ficus species, my analyzing focus are variation between genders and between habitats. The leaf phenology showed that F. virgate was a evergreen plant species and the life span of leaves lasted about one year. New leaves germinated before old leaves fell off , thus the total leaves maintained stable on the tree. In contrast, the fig phenology showed two main growing seasons, early spring to early summer, and late summer to autumn. In addition, the fig phenology showed obvious difference between two study sites as well as between sexes of trees, the amount of leaves and figs on female trees were higher at Taipei than at Bitou, but those on male trees were opposite. The spatial variation is consistent with the microclimate variation. Urban heat island effect should be stronger at Taipei city, while Bitou cape was relatively cold and wet due to facing beach and northeast monsoon. On the whole, the growth of F. virgata in northern Taiwan was very stable, although there is its northern limitation for distribution. The crops of two study sites showed similar patterns, the male trees carried continuous crops for all year round and the female trees only bred crops during warm and humid seasons. However, the size and weight of figs showed significantly sexual variation, female figs were bigger and heavier than those of male figs. The female figs should load more nutrients to help seed developing and attract frugivores. In addition, while the male and female plants of F. virgate generally showed high within-trees synchrony, but the evenness varied with different sexes as well as sites. The evenness was higher for female trees at Taipei, but it was higher for male trees at Bitou cape. These variation may related with adaptive strategy for different environments, and to maintain wasps population and expansion of this Ficus population. In future research, the analysis of the composition of wasps and seeds can be added to understand the growth pattern of male and female trees in different seasons. So that we can know more about the phenology of dioecious Ficus, and more helpful for the conservation for tropical plants.