A reduced role for water transport during the Cenozoic evolution of epiphytic Eupolypod ferns
A reduced role for water transport during the Cenozoic evolution of epiphytic Eupolypod ferns
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DOI：
10.1111/nph.18667
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发表时间：
2023-01-05
期刊：
影响因子：
9.4
通讯作者：
Watkins，James E.
中科院分区：
文献类型：
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作者：
Pittermann，Jarmila;Baer，Alex;Watkins，James E.
白垩纪-新生代热带森林的扩张创造了冠层空间，随后被包括真足类蕨类植物在内的各种附生植物群落所占据。真足类动物在这个压力更大的生态位中繁殖，在那里，竞争更低，使数千种物种能够适应辐射。在这里，我们研究木质部特征是否有助于形成新生代欧洲多足类蕨类植物的辐射。研究了39种属于真足类I和真足类II支系的叶柄木质部解剖特征，分别占据了附生、半附生和陆生生态位，并评估了其中一部分物种的栓塞易感性。向冠层过渡与木质部含量减少和管胞直径减小有关，但对栓塞的易碎性和坑膜厚度没有差异。系统发育分析支持了在真足类动物1种中与减少水分转运有关的性状的选择。我们假设在真多足类附生植物中，选择倾向于通过较厚的叶片和较低的气孔密度保持水分，而不是较高的水分输送率。因此，叶片失水减少，木质部数量减少，管胞直径变窄。与水分保持相关的性状在陆生真足类蕨类植物中很明显，这可能使这一分支倾向于树冠辐射。
The Cretaceous–Cenozoic expansion of tropical forests created canopy space that was subsequently occupied by diverse epiphytic communities including Eupolypod ferns. Eupolypods proliferated in this more stressful niche, where lower competition enabled the adaptive radiation of thousands of species. Here, we examine whether xylem traits helped shape the Cenozoic radiation of Eupolypod ferns.We characterized the petiole xylem anatomy of 39 species belonging to the Eupolypod I and Eupolypod II clades occupying the epiphytic, hemiepiphytic, and terrestrial niche, and we assessed vulnerability to embolism in a subset of species.The transition to the canopy was associated with reduced xylem content and smaller tracheid diameters, but no differences were found in species vulnerability to embolism and pit membrane thickness. Phylogenetic analyses support selection for traits associated with reduced water transport in Eupolypod 1 species.We posit that in Eupolypod epiphytes, selection favored water retention via thicker leaves and lower stomatal density over higher rates of water transport. Consequently, lower leaf water loss was coupled with smaller quantities of xylem and narrower tracheid diameters. Traits associated with water conservation were evident in terrestrial Eupolypod 1 ferns and may have predisposed this clade toward radiation in the canopy.