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，或因气候变化进一步加剧。针对这类物种与气候变化的交互作用的预测，在南大洋岛屿（Southern Ocean islands）中最为显著——该区域的环境正趋于改善，预计将缓解啮齿动物所面临的温度与资源限制。然而，目前该区域仍缺乏确凿证据表明啮齿动物种群会随气候变化发生改变，也尚未有研究证实此类种群变化会对陆地环境产生相关影响。本研究基于亚南极马里恩岛（sub-Antarctic Marion Island）逾三十年的实地调查数据，开展实证检验，探讨了两个核心问题：其一，小鼠种群是否随时间发生了显著变化；其二，此类变化是否与非生物条件（abiotic conditions）的改变存在显著关联。此前有研究将无脊椎动物（invertebrate）种群的变化归因于小鼠捕食，但鲜有开展明确的种群统计分析，本研究也对该类种群变化进行了考察，以判断其是否与小鼠种群的变动存在关联。1979-1980年至2008-2011年间，该岛年度峰值密度下的小鼠总数量增长了530.0%。此次种群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。小鼠直接降低了无脊椎动物的种群密度，部分生境的无脊椎动物生物量降幅可达两个数量级。这类无脊椎动物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适宜的生存条件，其造成的生态影响严重程度也将随之升高。同时，本研究也强调了啮齿动物根除（rodent eradication）工作对于受损岛屿生态修复的重要意义。