Plant-pollinator mutualisms may be disrupted by alien ants. Such threats are likely to vary spatio-temporally and with other biological invasions, but these aspects are rarely studied. We examined a threatened island endemic scrambler (Roussea simplex, Rousseaceae) about a decade after its pollination by an endemic reptile was found to be disrupted by an invasive alien ant and we investigated whether progressive invasion by plants has an influence on alien ant distribution. We quantified ant-infestations of the scrambler’s flowers and the vertical distribution of alien ants in the habitats through baiting experiment over 2 years and characterised the height of plants within habitat patches that face contrasting levels of alien plant invasion. Two alien and one native ant species were found visiting the flowers, namely Technomyrmex albipes, Anoplolepis gracilipes and Plagiolepis madecassa respectively. Few flowers (6.1%) had alien ants and ant-infested flowers occurred mostly nearer the ground. Mean alien ant abundance varied annually for A. gracilipes but not for T. albipes which however is much rarer than a decade previously. Alien ant-occupied baits showed higher probability of occurring predominantly nearer the ground. Roussea plants were much shorter where alien plant invasion is high, compared to where habitats are well-preserved. The severity of alien ant-infestation that leads to mutualism-disruption varies spatially and at different time scales. As alien plant invasion progresses, the resulting higher native plants’ mortality causes Roussea to lose its supporting host plants and collapse closer to the ground where it faces greater infestation of the alien ants that are documented to disrupt its pollination. Incorporating spatio-temporal variation of threats and unravelling possible interactions between sympatric invasive alien species should be important considerations for conservation managers.

植物授粉媒介的共生关系可能会被外来蚂蚁破坏。此类威胁可能会随时间和其他生物入侵而变化，但是很少研究这些方面。我们检查了一个濒临灭绝的岛屿地方性扰乱者（Roussea simplex卢梭科）被一种地方性爬行动物授粉后约十年，被入侵的外来蚂蚁破坏，我们调查了植物的渐进入侵是否会对外来蚂蚁的分布产生影响。我们通过2年的诱饵实验，量化了扰乱者的花朵的蚂蚁侵扰和栖息地中外来蚂蚁的垂直分布，并针对面临着不同外来植物入侵水平的栖息地斑块中的植物高度进行了表征。发现有两种外来蚂蚁物种和一种本地蚂蚁物种参观了花朵，分别是Technomyrmex albipes，Anoplolepis gracilipes和Plagiolepis madecassa分别。很少有花朵（6.1％）带有外来蚂蚁，并且被蚂蚁侵扰的花朵大多发生在地面附近。平均外星人蚂蚁丰度变化，每年A.细梗而不是T. albipes然而这是十几年来非常罕见前面。外来蚂蚁占据的诱饵显示出主要发生在靠近地面的可能性更高。与生境保存完好的地方相比，外来植物入侵程度高的罗西植物要短得多。导致相互破坏的外来蚂蚁侵扰的严重性在空间上和在不同的时间尺度上是变化的。随着外来​​植物入侵的进行，由此导致的更高的原生植物死亡率导致了Roussea失去其支持的寄主植物，并在接近地面的地方倒塌，在地面上，外来蚂蚁受到更大的侵扰，据记载，这些蚂蚁会破坏其授粉。纳入威胁的时空变化并阐明同伴入侵外来物种之间可能的相互作用，应该是保护管理人员的重要考虑因素。