Long-term cloud forest response to climate warming revealed by insect speciation history

Montane cloud forests are areas of high endemism, and are one of the more vulnerable terrestrial ecosystems to climate change. Thus, understanding how they both contribute to the generation of biodiversity, and will respond to ongoing climate change, are important and related challenges. The widely accepted model for montane cloud forest dynamics involves upslope forcing of their range limits with global climate warming. However, limited climate data provides some support for an alternative model, where range limits are forced downslope with climate warming. Testing between these two models is challenging, due to the inherent limitations of climate and pollen records. We overcome this with an alternative source of historical information, testing between competing model predictions using genomic data and demographic analyses for a species of beetle tightly associated to an oceanic island cloud forest. Results unequivocally support the alternative model: populations that were isolated at higher elevation peaks during the Last Glacial Maximum are now in contact and hybridising at lower elevations. Our results suggest that genomic data is a rich source of information to further understand how montane cloud forest biodiversity originates, and how it is likely to be impacted by ongoing climate change.

山地云雾林是特有性极高的区域，也是受气候变化影响最为脆弱的陆地生态系统之一。因此，厘清山地云雾林如何推动生物多样性的形成，以及其将如何响应持续的气候变化，是兼具重要性与关联性的科学难题。目前学界广泛认可的山地云雾林动态模型认为，全球气候变暖会导致其分布范围上限向高海拔区域推进。然而，受限于有限的气候数据，有研究支持另一套替代模型：该模型提出气候变暖会使得分布范围上限向低海拔区域退缩。由于气候与孢粉记录本身存在固有局限，对这两种模型进行验证存在较大难度。本研究借助一种替代性的历史信息来源，针对一种与大洋岛云雾林紧密共生的甲虫类群，利用基因组数据与种群动态分析方法对两种竞争性模型的预测结果进行验证，从而解决了上述难题。研究结果明确支持替代模型：在末次盛冰期（Last Glacial Maximum）被隔离于高海拔山峰的种群，如今已在低海拔区域发生接触并产生杂交。本研究结果表明，基因组数据是进一步解析山地云雾林生物多样性起源，以及其将如何受到持续气候变化影响的宝贵信息来源。