菊科外來歸化植物之入侵性初步探討

Potential Asteraceae Invaders in Taiwan: Insights from the Flora and Herbarium Records of Casual and Naturalized Alien Species

有鑒於外來植物在侵入原生環境之前皆須經過歸化（naturalization）階段，本研究依據先前所發表的台灣歸化植物名錄，針對歸化之菊科植物基本資料進行整理與探討，藉以瞭解潛在入侵菊科植物之生物特性及來源。並藉由分析標本記錄，預測菊科歸化植物之入侵性（invasiveness）。結果顯示，菊科歸化植物共有51種，其中44%為入侵物種，然而，多數的物種的引進原因不明。美洲的熱帶地區是台灣菊科歸化植物的主要原生地，歐洲及美洲溫帶地區其次。大多數的菊科歸化植物為一年生，入侵性強的多年生植物則可能造成環境問題。這些外來的植物多以不同的速度擴散，即使是具有相同駐在時間（minimum residence time）的同屬種類，亦有不同的表現。據我們的推測及分析顯示，此一不同的擴散趨勢，可作為這些物種入侵能力的指標。

Naturalization has been shown to be one of the primary stages of plant invasions; therefore, studies on naturalized plant species may generate valuable insights of possible invaders and invasions. Background information of casual and naturalized Asteraceae species provided by a comprehensive list of casual and naturalized species in Taiwan was examined to estimate the basic biological traits and geological origins of potential invasive species in this study. Besides, herbarium records were collected and analyzed to predict the invasiveness of casual and naturalized Asteraceae species. Our results showed that 44.0% out of the 51 casual and naturalized Asteraceae species were classified as invasive in the field, and a notable portion of these species were probably introduced accidently. Tropical Americas were the most important origins of casual and naturalized Asteraceae species, followed by Europe and temperate Americas. Most of the casual and naturalized Asteraceae species were annual herbs, and a few perennial species categorized as invasive may cause profound environmental problems. The herbarium record showed that species possessed different numbers of localities within the same time frame. We suggested that casual and naturalized Asteraceae species collected in more localities are more invasive than those species found in fewer localities within the same period of time.