Qian Hong, Kessler Michael
Research and Collections Center, Illinois State Museum, Springfield, IL 62703, USA.
Department of Systematic and Evolutionary Botany, University of Zurich, Zurich, Switzerland.
Ann Bot. 2025 May 9;135(5):991-1000. doi: 10.1093/aob/mcaf013.
Mount Kinabalu is an isolated, geologically young mountain (Pliocene and early Pleistocene) in northern Borneo harbouring a highly diverse flora with a high level of endemism. It is one of the global centres of fern diversity, but how this diversity has evolved has not been studied to date. We assess patterns of evolutionary legacies in the fern flora of Mount Kinabalu, with an emphasis on testing the tropical niche conservatism hypothesis.
We used several metrics of phylogenetic structure, including phylogenetic diversity (PD), mean nearest taxon distance (MNTD), mean pairwise distance (MPD), and their respective standardized effect sizes (PDses, MNTDses and MPDses), which represent different depths of evolutionary history, to investigate patterns of evolutionary legacies in the fern flora of Mount Kinabalu.
We found that there was a decrease of PDses with elevation, reflecting a tropical origin of ferns and a gradual evolutionary adaptation to colder environments by fewer successive lineages. However, when separating the evolutionary old non-polypod lineages from the modern polypod radiation, we found a decrease of MNTD with elevation for the former, reflecting an ongoing upslope evolutionary trend, whereas for the modern polypod radiation, the inverse was true. Within the polypods, terrestrial and epiphytic species also showed different patterns, with the former showing a hump-shaped pattern for all phylogenetic diversity metrics, whereas the latter showed a more or less linear decline. Again, this suggests different evolutionary histories for ferns inhabiting the forest floor and canopy, due to the influence of the different habitat conditions. Finally, we found that mean annual temperature had a much stronger effect on phylogenetic diversity metrics than annual precipitation.
We found that the current fern assemblages on Mount Kinabalu show a strong evolutionary legacy that mirrors that of other mountains, suggesting a global consistency in phylogenetic diversity patterns of ferns along elevational transects, presumably due to a combination of dispersal between mountains and evolutionary convergence.
基纳巴卢山是婆罗洲北部一座孤立的、地质年代较新的山脉（上新世和早更新世），拥有高度多样化且特有程度高的植物群。它是全球蕨类植物多样性中心之一，但这种多样性是如何演化的，迄今为止尚未得到研究。我们评估了基纳巴卢山蕨类植物群的进化遗留模式，重点是检验热带生态位保守性假说。
我们使用了几种系统发育结构指标，包括系统发育多样性（PD）、平均最近类群距离（MNTD）、平均成对距离（MPD）及其各自的标准化效应大小（PDses、MNTDses和MPDses），这些指标代表了不同深度的进化历史，以研究基纳巴卢山蕨类植物群的进化遗留模式。
我们发现，PDses随海拔升高而降低，这反映了蕨类植物的热带起源以及较少的连续谱系对较冷环境的逐渐进化适应。然而，当将进化古老的非水龙骨谱系与现代水龙骨辐射谱系分开时，我们发现前者的MNTD随海拔升高而降低，反映了持续的上坡进化趋势，而对于现代水龙骨辐射谱系，情况则相反。在水龙骨类中，陆生和附生种类也表现出不同的模式，前者在所有系统发育多样性指标上呈现驼峰状模式，而后者则或多或少呈线性下降。同样，这表明由于不同栖息地条件的影响，栖息在森林地面和树冠层的蕨类植物有着不同的进化历史。最后，我们发现年平均温度对系统发育多样性指标的影响比年降水量大得多。
我们发现，基纳巴卢山目前的蕨类植物组合显示出强烈的进化遗留，这与其他山脉的情况相似，表明沿海拔梯度蕨类植物系统发育多样性模式具有全球一致性，这可能是山脉间扩散和进化趋同共同作用的结果。
