1. Invasive species pose one of the most serious global threats to biodiversity. Investigations into the interactions of native and non‐native species focus on the impacts of single species, despite being embedded in a network of direct and indirect interactions between multiple species and their environments.
2. We developed 1‐km² resolution, single‐species and multi‐species occupancy models using quantitative camera trap data collected by citizen scientists at 332 sites in a regional survey comprising the 14,130 km² of Northern Ireland.
3. Recent research suggests that native red and invasive grey squirrels in Britain and Ireland are linked by resource and disease‐mediated competition, and by a shared enemy, the European pine marten. We demonstrate that the presence of the pine marten reverses red squirrel replacement by grey squirrels on a regional basis, with red squirrel occupancy positively affected by exposure to pine marten. In contrast, the grey squirrel has a strongly negative response to the presence of pine marten.
4. Modelling habitat suitability of pine marten and both squirrel species suggests that, despite the potentially strong effect of a recovering population of pine martens in controlling grey squirrel distribution, the latter is likely to persist in urban refugia that are either inaccessible or avoided by the pine marten.
5. Synthesis and applications. Sustainable recovery of both the red squirrel and the pine marten across the wider landscapes of Ireland, Scotland and Northern England seems probable, while in Southern England and Wales, although possible, chances are more remote. Increasing native woodland cover on a landscape scale to facilitate pine marten recovery may assist in realizing this scenario. Despite the ongoing recovery of the pine marten, and resultant declines in grey squirrels, isolated populations are likely to persist in urban areas. Human‐lead control of grey squirrel populations in urban refugia requires urgent funding and implementation to avoid the development of novel genotypes in grey squirrel source populations that enable the species to better avoid predation by the pine marten.

中文翻译：

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入侵性灰松鼠种群的减少可能会持续在避难所中，因为本地捕食者的恢复会逆转松鼠物种的替代

1. 入侵物种构成了对生物多样性最严重的全球威胁之一。尽管已嵌入多种物种与其环境之间的直接和间接相互作用的网络中，但对本土和非本土物种相互作用的调查仍侧重于单个物种的影响。
2. 我们使用定量科学家捕获的定量照相机陷阱数据，在包括北爱尔兰的14,130 km ²的区域调查中，开发了1 km ²分辨率，单物种和多物种占用模型。
3. 最近的研究表明，英国和爱尔兰的本地红松鼠和入侵性灰松鼠与资源和疾病介导的竞争以及共同的敌人欧洲松貂联系在一起。我们证明，在区域基础上，松貂的存在会逆转灰松鼠对红松鼠的替代，而红松鼠的占有率会受到松貂的正面影响。相反，灰松鼠对松貂存在强烈的负面反应。
4. 对松貂和两种松鼠物种的栖息地适应性进行建模表明，尽管恢复中的松貂种群在控制灰松鼠分布方面具有潜在的强大作用，但松鼠可能无法在城市避难所中避免后者逃避。
5. 综合与应用。红松鼠和松貂在爱尔兰，苏格兰和英格兰北部更广阔的土地上的可持续恢复似乎是可能的，而在英格兰南部和威尔士，尽管可能，但机会却很少。在景观尺度上增加原生林地覆盖以促进松貂的恢复可能有助于实现这种情况。尽管松貂不断恢复，灰松鼠因此减少，但偏远地区的种群仍可能持续存在。人为控制城市避难所中灰松鼠种群需要紧急资金和实施，以避免灰松鼠种群中出现新的基因型，从而使该物种更好地避免松貂的捕食。