末次盛冰期以来观光木的潜在地理分布变迁

观光木(Tsoongiodendron odorum)是木兰科的古老残遗物种, 目前正面临严峻的生存威胁, 属于极小种群濒危植物。通过生态位模型(ENM)能够重建观光木地理分布格局的历史变迁, 探究气候变化对该物种分布的影响, 并了解其地理分布与气候需求间的关系, 从而为全球变暖背景下观光木的保护提供理论基础。该文基于96条现代分布记录和8个环境变量, 采用最大熵(MaxEnt)模型模拟观光木在末次盛冰期、全新世中期、现代和未来(2061-2080年, RCP 8.5)的潜在分布区, 利用SDM toolbox分析观光木的地理空间变化, 并综合贡献率、置换重要值和Jackknife检验来评估气候因子的重要性。研究结果表明: (1)观光木的高度适生区在南岭地区, 末次盛冰期时没有大尺度向南退缩, 很可能在山区避难所原地存活; (2)在全新世中期和未来两个增温的气候情境下, 观光木的分布区均表现为缩减, 其中未来分布的减幅更大, 表明气候变暖对观光木的生长有一定的负面影响; (3)总体上看, 观光木各个时期的地理分布范围相对稳定, 说明观光木对气候变化有一定的适应能力, 人为活动或自身繁育问题可能是致濒的重要原因, 并建议对广东和广西群体进行优先保护。

Changes in potential geographical distribution of Tsoongiodendron odorum since the Last Glacial Maximum

Aims Tsoongiodendron odorum is an ancient relic species belonging to the family Magnoliaceae, but it is labelled endangered plant with extremely small populations and facing serious threats to its wild survival now. Using Ecological Niche Modelling (ENM) to hindcast historical changes in its distribution during the Last Glacial Maximum (LGM), this study aims to explore the impact of climate change on the distribution of T. odorum, and to evaluate the relationship between species distribution and environmental variables. The results of this study could contribute to the conservation of T. odorum in the context of global warming.
Methods Based on 96 modern geographical distribution records and 8 bioclimatic variables, we simulated the potential distribution of T. odorum during the LGM, Mid-Holocene, present and future (period of 2061-2080 in the Representative Concentration Pathway 8.5 climate scenario) with MaxEnt model. The changes in species distribution through time were analyzed by SDM toolbox, while the importance of bioclimatic variables was evaluated by percent contribution, permutation importance and Jackknife test.
Important findings (1) The highly suitable region for T. odorum was Nanling region, and this area might be the refuge where T. odorum survived in situ during the LGM because only slightly southward retreat in distribution was detected in this region during the LGM. (2) In the two warming climate scenarios (Mid-Holocene and future), the area of the suitable region was reduced, and the decrease of future distribution is greater than that during the Mid-Holocene, which suggests that warming climate might have a negative impact on the distribution of T. odorum. (3) Overall the stability of distribution range of T. odorum in each period indicates the climate adaptation of this species. Human activity or self-breeding problem was likely the significant cause leading to endangered condition. Guangdong and Guangxi should be regarded as priority conservation areas as shown by our results.