Differences in exploitation and interference ability between two dominant ants: the invasive Argentine ant (Linepithema humile) and Tapinoma magnum

The Argentine ant is a highly invasive species that can cause significant ecosystem alterations. Its spread in the invaded areas is usually associated with the displacement of native ant species by means of strong interference competition mechanisms. According to recent studies, Tapinoma nigerrimum s.l., a native Mediterranean ant, can potentially limit the expansion of the Argentine ant. The aim of the present study is to determine the ethological features that discriminate against the ability of L. humile and T. magnum (nigerrimum complex) to exploit a trophic resource both in the presence and in the absence of the competitor. We conducted behavioural assays on experimental colonies using foraging arenas in a laboratory experiment. Linepithema humile colonies showed the ethological profile typical of the species, as they carried out more intense recruitment, initially concentrated on the whole foraging site rather than on the bait. Linepithema humile workers were more aggressive and fought cooperatively during inter-specific interactions. Tapinoma magnum colonies apparently showed a more food-oriented profile as they were faster in the search for food and concentrated the recruitment on it rather than on the whole foraging site. Tapinoma magnum workers tried to avert the competitor using threat postures rather than physical aggression. Tapinoma magnum colonies were systematically excluded by L. humile colonies from the trophic resource and underwent a visible reduction in surface activity. These results suggest that L. humile used a different and more effective interference competition strategy compared to T. magnum.

阿根廷蚁（Linepithema humile）是一种极具入侵性的物种，可对生态系统造成显著改变。其在入侵区域的扩散通常与通过强力干扰竞争机制排挤本地蚁类密切相关。近期研究表明，地中海本土蚁类黑腹铺道蚁复合种（Tapinoma nigerrimum s.l.）具备限制阿根廷蚁扩张的潜在能力。本研究旨在明确可区分阿根廷蚁与巨首铺道蚁（Tapinoma magnum，隶属于黑腹铺道蚁复合种）利用营养资源能力的行为学特征，无论竞争者存在与否。我们在实验室实验中利用觅食竞技场对实验蚁群开展行为测定。阿根廷蚁群展现出该物种典型的行为学特征：其招募行为更为强烈，初始活动会集中于整个觅食场地而非诱饵点位。阿根廷蚁工蚁攻击性更强，且在种间相互作用中会协同作战。巨首铺道蚁群则明显呈现出更偏向食物导向的行为模式：其搜寻食物的速度更快，且会将招募行为集中于诱饵而非整个觅食场地。巨首铺道蚁工蚁会通过威慑姿态而非物理攻击来规避竞争者。阿根廷蚁群会系统性地将巨首铺道蚁群排挤在营养资源之外，并使其地表活动量出现显著下降。上述结果表明，相较于巨首铺道蚁，阿根廷蚁采用了更为独特且高效的干扰竞争策略。