Data from: Climate change leads to increasing population density and impacts of a key island invader

The considerable threats of invasive rodents to island biodiversity are likely to be compounded by climate change. Forecasts for such interactions have been most pronounced for the Southern Ocean islands where ameliorating conditions are expected to decrease thermal and resource restrictions on rodents. Firm evidence for changing rodent populations in response to climate change, and demonstrations of associated impacts on the terrestrial environment, are nonetheless entirely absent for the region. Using data collected over three decades on sub-Antarctic Marion Island, we tested empirically whether mouse populations have changed through time and whether these changes can be associated significantly with changing abiotic conditions. Changes in invertebrate populations, which have previously been attributed to mouse predation, but with little explicit demographic analysis, were also examined to determine whether they can be associated with changing mouse populations. The total number of mice on the island at annual peak density increased by 530.0% between 1979-80 and 2008-11. This increase was due to an advanced breeding season, which was robustly related to the number of precipitation-free days during the non-breeding season. Mice directly reduced invertebrate densities, with biomass losses of up to two orders of magnitude in some habitats. Such invertebrate declines are expected to have significant consequences for ecosystem processes over the long term. Our results demonstrate that as climate change continues to create ameliorating conditions for invasive rodents on sub-Antarctic islands, the severity of their impacts will increase. They also emphasize the importance of rodent eradication for the restoration of invaded islands.

入侵啮齿动物（invasive rodents）对岛屿生物多样性（island biodiversity）造成的严重威胁，大概率会因气候变化（climate change）而进一步加剧。针对这类物种互作的预测，在南大洋岛屿（Southern Ocean islands）中最为显著：预计当地生境条件将更趋适宜，从而缓解啮齿动物面临的温度与资源限制。然而，该区域迄今仍缺乏能够证明啮齿动物种群随气候变化发生改变的确凿证据，也尚未有研究证实其对陆地环境（terrestrial environment）产生的相关影响。本研究依托在亚南极马里恩岛（sub-Antarctic Marion Island）收集的三十年跨度数据，通过实证检验，探究了家鼠种群是否随时间发生变化，以及这些变化是否与非生物环境条件（abiotic conditions）的改变存在显著关联。此前有研究将无脊椎动物（invertebrate）种群变化归因于家鼠的捕食行为，但相关分析极少涉及明确的种群统计分析（demographic analysis）；本研究同时对无脊椎动物种群变化展开考察，以判断其是否与家鼠种群的变动存在关联。1979-1980年至2008-2011年间，该岛屿家鼠种群的年度峰值总数量增长了530.0%。这一增长源于繁殖季提前，而繁殖季提前与非繁殖季的无降水天数显著相关。家鼠直接降低了无脊椎动物的种群密度，部分生境中的无脊椎动物生物量损失最高可达两个数量级。此类无脊椎动物种群的减少，预计将对长期生态系统过程（ecosystem processes）产生重大影响。本研究结果表明：随着气候变化持续为亚南极岛屿的入侵啮齿动物创造更趋适宜的生境条件，其生态影响的严重程度也将不断加剧；同时也凸显了啮齿动物根除（rodent eradication）工程对恢复受入侵岛屿生态系统的重要性。