台灣植物種子大小及其與環境的關係

Abstract

種子大小是植物生活史中重要的關鍵角色，影響到種子傳播能力與小苗的競爭力。特別是在逆境(遮蔭、乾旱、貧瘠)或是高競爭壓力的環境下，儲備養分多的大型的種子的物種表現出較高的更新能力。因此在不同的逆境程度下，植物的種子大小表現是可預測的。除了環境逆境外，種子大小在植物生長型、傳播模式間一致的變化趨勢也必須一併考慮。 台灣位於熱帶、亞熱帶交會處，幾乎涵蓋全世界所有的生育地類型。多樣異質的環境孕育出豐富的生物多樣性，適合進行植物生活史特性間與環境因子之間的研究，以檢驗目前所提出的植物分布的假說。因此本研究利用文獻蒐集的方式取得台灣被子植物生活史特性(life history traits)的資料。這些資料包括種子的大小(seed size)、種子傳播特徵(seed dispersal mode)以及生活型。並配合臺灣國家植群多樣性調查及製圖計劃中物種分布、植物社會組成的資料。利用這些資料來討論植物生活史特性之間的關聯以及與植物社會組成上、環境因子的相關性，藉此了解這些特性在生態上分布的特色。 研究結果顯示在種子大小在生長型、傳播模式間具有顯著差異。在物種間，體型大或是具有肉質果實(動物傳播型)的植物種類傾向產生大型的種子。影響群落種子大小表現氣候因子中，溫度是最重要因素。溫度為海拔、緯度上種子大小的變異的主要影響因素。在溫暖潮濕的亞熱帶海島地區，雨量、輻射對植物種子大小的變化影響不大。

Seed size is an important plant life history trait, determining seed dispersal ability and seedling establishment. Particularly in stress (shaded, dry) or with higher competition pressure, larger seed species with much reserve can have a higher establishment success. Therefore, seed size of plant is predictably under different stress conditions. In addition to environmental stress, the constant trends among seed size in plant growth forms and dispersal modes need to be considered. Taiwan is located between tropical and subtropical areas, and contains almost all types of habitats in the world. Heterogeneous environment creates extraordinary biodiversity. It is suitable for verifying the distribution hypothesis about plant life history characteristics and environmental factors. To date there no relevant research in Taiwan. Therefore, I compiled a dataset of life history traits of angiosperms in Taiwan trough literatures survey. This information included seed size, seed dispersal syndrome, and life form. As for species distribution and plant community composition, I used the data from National Vegetation Survey and Mapping Program in Taiwan. The study showed the significant difference between growth forms and dispersal modes. Among species, those with larger body or fleshy fruit tend to have larger seed. Temperature is most important climatic factors affect performance of community seed size. Temperature is the main factor of seed size variation along altitude and latitude. In the warm, humid subtropical island regions, rainfall and solar radiation have little effect on variation of plant seed size.