Taiwania

Introduction of a non-native lineage is linked to the recent black cocoa ant, Dolichoderus thoracicus (Smith, 1860), outbreaks in Taiwan The black cocoa ant, Dolichoderus thoracicus (Smith), is widely distributed across the Indomalayan region including Taiwan. Until the recent localized outbreaks in central Taiwan, this ant has never been considered as a pest. The current study tested if an introduction of non-native lineage(s) potentially contributes to the ant’s sudden outbreaks in Taiwan by analyzing phylogenetic relationships of D. thoracicus in Taiwan and Southeast Asia. Our results showed that all ants were grouped into two major mitochondrial clades (Clade I and II) separated by a p-distance of 0.0414. Clade I is widespread in Taiwan and represented by six haplotypes that are genetically similar to the haplotypes from the Philippines, indicating that these ants are likely a result of range expansion of the Philippine lineage(s). In contrast, ants from central Taiwan harbor a single Clade II haplotype that is predominantly found in the samples collected from the Indochina region. Coupled with the low genetic diversity, Clade II D. thoracicus in Taiwan was most likely introduced from the Indochina region. The possibility is further supported by the fact that most D. thoracicus intercepted at the Taiwanese borders had an Indochina origin. Overall, this study suggests that a non-native lineage is responsible for the recent outbreaks of this ant in Taiwan, highlighting a potential research avenue for future research on the association between the “pest” trait and non-native genetic variant in invaded area.

非本土谱系的引入与近期台湾地区黑可可蚁（Dolichoderus thoracicus Smith, 1860）的爆发密切相关。黑可可蚁（Dolichoderus thoracicus Smith）广泛分布于印度-马来群岛地区，包括台湾。直至近期在台湾中部地区出现的局部爆发，该蚁种从未被视为害虫。本研究旨在通过分析台湾及东南亚地区D. thoracicus的进化关系，探究非本土谱系引入是否可能为该蚁种在台湾的突发性爆发提供潜在原因。研究结果表明，所有蚁种被分为两个主要的线粒体类群（类群I和II），两者之间的遗传距离为0.0414。类群I在台湾广泛分布，由六个基因型相似于菲律宾基因型的单倍型所代表，表明这些蚁种很可能是菲律宾谱系扩张的结果。相比之下，来自台湾中部的蚁种携带单个类群II单倍型，该单倍型主要在从印度支那地区收集的样本中找到。结合较低的遗传多样性，台湾地区的类群II D. thoracicus最有可能源自印度支那地区。这一可能性进一步得到支持，因为大多数在台湾边境截获的D. thoracicus均具有印度支那的起源。总体而言，本研究表明非本土谱系是导致该蚁种在台湾近期爆发的原因，为未来研究入侵区域“害虫”性状与非本土遗传变异之间的关系提供了潜在的研究方向。