Data from: Testing the effects of ant invasions on non-ant arthropods with high-resolution taxonomic data

Invasions give rise to a wide range of ecological effects. Many invasions proceed without noticeable impacts on the resident biota, whereas others shift species composition and even alter ecosystem function. Ant invasions generate a broad spectrum of ecological effects, but controversy surrounds the extent of these impacts, especially with regard to how other arthropods are affected. This uncertainty in part results from the widespread use of low-resolution taxonomic data, which can mask the presence of other introduced species and make it difficult to isolate the effects of ant invasions on native species. Here, we use high-resolution taxonomic data to examine the effects of Argentine ant invasions on arthropods on Santa Cruz Island, California. We sampled arthropods in eight pairs of invaded and uninvaded plots and then collaborated with taxonomic experts to identify taxa in four focal groups: spiders, bark lice, beetles, and ants. Spiders, bark lice and beetles made up approximately 40% of the 9868 non-ant arthropod individuals sampled; the majority of focal group arthropods were putatively native taxa. Although our results indicate strong negative effects of the Argentine ant on native ants, as is well documented, invaded and uninvaded plots did not differ with respect to the richness, abundance or species composition of spiders, bark lice and beetles. One common, introduced species of bark louse was more common in uninvaded plots than in invaded plots, and including this species into our analyses changed the relationship between bark louse richness versus L. humile abundance from no relationship to a significant negative relationship. This case illustrates how failure to differentiate native and introduced taxa can lead to erroneous conclusions about the effects of ant invasions. Our results caution against unqualified assertions about the effects of ant invasions on non-ant arthropods and more generally demonstrate that accurate assessments of invasion impacts depend on adequate information about species identity.

生物入侵可引发多样化的生态效应。多数入侵事件未对本地生物群(resident biota)产生可观测的影响，而部分入侵则会改变物种组成(species composition)，甚至改变生态系统功能(ecosystem function)。蚂蚁入侵同样会产生广谱性的生态效应，但其影响范围尚存争议，尤其是在对其他节肢动物(arthropods)的影响层面。这种不确定性部分源于研究中广泛采用低分辨率分类学数据(taxonomic data)——这类数据可能掩盖其他外来物种(introduced species)的存在，且难以精准剥离蚂蚁入侵对本地物种(native species)的影响。
本研究借助高分辨率分类学数据，针对加利福尼亚州圣克鲁兹岛的阿根廷蚁(Linepithema humile)入侵对节肢动物的影响开展研究。我们在8组配对的入侵样地与未入侵样地中采集节肢动物样本，并联合分类学专家对4类目标类群(focal groups)进行物种鉴定：蜘蛛(spiders)、啮虫(bark lice)、甲虫(beetles)以及蚂蚁(ants)。本次采集的9868头非蚂蚁节肢动物(non-ant arthropod)个体中，蜘蛛、啮虫与甲虫合计占比约40%；目标类群节肢动物的绝大多数为疑似本地类群(putatively native taxa)。尽管研究结果证实了阿根廷蚁对本地蚂蚁的强烈负面影响（这与已有研究结论一致），但入侵与未入侵样地在蜘蛛、啮虫和甲虫的物种丰富度(richness)、个体丰度(abundance)及物种组成(species composition)方面均未表现出显著差异。
有一种常见的外来啮虫在未入侵样地中的个体丰度显著高于入侵样地；将该物种纳入分析后，啮虫物种丰富度与阿根廷蚁(L. humile)种群密度间的相关性从无显著关联转变为显著负相关。这一案例表明，若未能区分本地与外来类群，可能会得出关于蚂蚁入侵影响的错误结论。本研究结果警示，不应未经限定地断言蚂蚁入侵对非蚂蚁节肢动物的影响；更广泛而言，准确评估入侵影响，有赖于对物种身份的精准认知。