入侵紅火蟻之族群生物學與其入侵性之關係

Abstract

入侵種於全球的傳播已嚴重威脅全球生態系，並造成大量經濟損失，甚至危及人畜生命。對於這些物種全盤瞭解，尤其針對某些導致入侵成功之特殊生物特徵，對於預測入侵潛力以及採取有效防治方法有絕對正面之幫助。在眾多入侵物種中，社會性昆蟲，特別是已經造成許多危害之螞蟻類群，成為近來關注之議題。若就嚴重性以及對於人類生活直接衝擊之程度而言，入侵紅火蟻 (Solenopsis invicta，以下簡稱火蟻) 被認為是最具代表性的入侵螞蟻物種，加上於本世紀初之短短數年間成功定殖澳洲、台灣以及中國，若不加以採取必要防範措施，不難想像其全球分布的可能性。因此，本研究針對各種生物學角度，包括族群遺傳、社會性組織以及天敵脫離 (enemy release) 等論點，解析此物種入侵成功之因素。另外，進一步重建此螞蟻於當前入侵地間之可能傳播途徑，追溯可能來源族群。研究結果顯示，火蟻入侵台灣後所呈現之遺傳形式大致與美國族群相符，但仍具有與近期入侵事件導致族群結構改變之痕跡；火蟻族群中，兩種不同社會性組織，包括多蟻后以及單蟻后，生物學上之互補性可能有利於其成功入侵，以及入侵後之內穩態 (homeostasis) 維持；幾乎所有天敵 (除了影響力稍弱之物種) 皆不存在於近期入侵之火蟻族群中，顯示火蟻成功立足之主要因素也可能來自其脫離主要且致命之天敵物種；遺傳資料也顯示，美國最有可能為所有近期入侵族群之來源，族群之間並無基因交流且包含九次獨立入侵事件。本研究以多元角度切入探究火蟻入侵成功之因素，還原其全球入侵歷史，除了更廣泛瞭解火蟻入侵成功之因素，期能進一步將所得資訊應用於防治策略之擬定。

Invasive species are recognized as major threats to native biodiversity, public health, and agriculture, often resulting in considerable economic loss. The full understanding of species’ characteristics that potentially could be transformed to the factors underlying the invasion success may assist accurate prediction of invasion potential as well as development of control strategies. Many social insects, particularly ants, are well known as being damaging pests, and one of the most notorious invasive ant species is the red imported fire ant, Solenopsis invicta. Recent multiple successful invasions by this exotic pest into several continents raise the concern about its imminent worldwide spread from the existing populations. To understand the invasiveness of S. invicta, the present study explored several key components of this pest ant species including population genetics, social organization and patterns of release from natural enemies. Also, the global movement of this ant was constructed to ascertain whether particular routes of invasion are common. The combined results showed that (1) introduction of fire ant in Taiwan left a modest footprint on pattern of genetic structure, (2) the interaction in a complementary fashion between two distinct colony social forms, monogyne and polygyne, likely contribute to the invasion and subsequent spread of S. invicta in Taiwan, (3) the success of recently established S. invicta populations may result from decreased pressure from natural enemy species with strong fitness effects compared with those that are less detrimental, (4) the USA represents the most likely common source population of all recently introduced areas, and the current distribution of S. invicta worldwide results from at least nine independent introductions. Multiple analyses of a large amount of data on different aspects of S. invicta provide guidelines for understanding the success of this pest ant species, as well as provide crucial information for the development of appropriate management strategies and facilitate the complete picture of fire ant invasions.