穴居鋸針蟻的超級群落與微衛星標幟 – 台灣新興 引入針蟻亞科鋸針蟻之初探

Abstract

隨著人類活動擴張，許多物種被帶離其原生地，對全球生態和農業造成嚴重威脅。非洲穴居鋸針(Odontomachustroglodytes) 原生於非洲，近年來族群爆發於台灣西南部果樹園，對於台灣生態及農業經濟造成潛在危害。與此同時，穴居鋸針蟻也展現出超級群落的潛力，加深此物種潛在的侵略性。目前有關這種鋸針蟻的族群結構侵略特性及基因層面的研究十分有限，這將使得制定相對防治方針時缺乏參考資料。本研究旨在填補有關穴居鋸針蟻的知識缺口，了解其行為 模式、生殖策略和族群結構。 本研究收集了嘉義和高雄的穴居鋸針蟻族群，進行巢間攻擊行為實驗，以探討此物種是否存在超級群落。實驗結果顯示，不同巢的穴居鋸針蟻並未展現攻擊性，表示入侵族群間具有相容性，可能形成高密度蟻群壟斷周圍資源。由於目前非洲穴居鋸針蟻沒有可用的微衛星遺傳標記，本研究中利用次世代定序技術篩選微衛星基因座，測試20組標記後，篩選出11個具有多型性的遺傳標記進行遺傳分析。遺傳分析結果顯示穴居鋸針蟻只使用有性生殖模式，並且在等位基因上缺乏多樣性。族群分化分析顯示嘉義族群與高雄族群可分為兩個不同的族群，代表台灣的入侵族群有可能是多次入侵的。然而，嘉義的族群卻同時具有較低的等位 基因數，並且缺乏族群獨有的等位基因，使得嘉義的族群也有可能源自等位基因 數更高並且具有獨有的等位基因的高雄族群。 本研究不僅提供台灣的穴居鋸針蟻入侵族群在行為、生殖模式及族群結構上的資訊，也是鋸針蟻族內首次記錄到超級群落的特性。我們的研究有助於解析新入侵螞蟻族群的結構和特性，並為該物種的生物防治管理和策略制定提供生態習性與族群遺傳分化上的貢獻。

Human activities have facilitated the global spread of numerous invasive species. Among invasive insects, ants are particularly successful due to reproductive flexibility, including mechanisms like polygyny and asexual reproduction, which likely facilitate their establishment and expansion in new environments. Besides reproductive flexibility, some ant species develop “Supercoloniality”, where individuals from geographically disparate colonies recognize each other as colony members. Supercoloniality diminishes intraspecific competition and strengthens resource monopolization, allowing these ants to dominate native competitors and disrupt the entire ecosystem. Odontomachus troglodytes, a recently-invaded African Ponerinae that took root in the southern part of Taiwan, is suspected to possess traits similar to other successful invasive ants. Clarifying the social structure and reproductive mechanism of this alien species can contribute to its scarce studies and the development of effective prevention measures that may mitigate its impact on the native fauna. Twelve colonies were collected followed by ant-to-ant aggression assays that were conducted to test the hostility of the colonies within and between the two invaded regions: Chiayi and Kaohsiung. The aggressiveness of every pair was graded, with a total of 107 bioassay pairs exhibiting no aggressive behaviour toward non-nestmates up to 120 kilometers apart, suggesting that this newly invaded Ponerinae possess the fundament trait of supercoloniality, which would be the first record in the Odontomachini tribe and in the Ponerinae subgamily. Rapid antennation among different pairing groups were analyzed and the duration of rapid antennation over time was met with a steep decline from the second bout. Microsatellite genotyping with the assist of field and laboratory observations were used to clarify the breeding structure and reproductive mechanism of the invaded O. troglodytes populations. Twenty potential microsatellite loci were selected, of which 12 were successfully amplified and 11 were found to be polymorphic. The collected colonies exhibited a high percentage of polygyny, with none of the genotyping results of the colonies indicate a reproduction method outside of reproducing sexually. Additionally, eight out of the nine genotyped colonies produced diploid males and/or extracted diploid sperm, indicating the introduced populations are under inbreeding situation typical to newly invaded ant species. The population differentiation analysis suggests two distinct genetic clusters exist between the two regions, supporting the hypothesis of multiple invasions by two distinct populations, yet the allelic summary shows that the Chiayi region has less abundant allele composition and lacks regional private alleles, arguing the case of post- colonization genetic mutation due to geographical barriers after inland bridgehead expansion. Our study fills the knowledge gaps about this newly invaded ant species on both behavioral and molecular perspectives and serve as the fundamental base for future mitigation measurements to minimize the impact of this alien species on the native ecosystems of Taiwan.