Department of Life Science, National Taiwan Normal University, Taipei, Taiwan.
Department of Life Sciences, National Chung Hsing University, Taichung, Taiwan.
Ann Bot. 2024 Jun 7;134(1):71-84. doi: 10.1093/aob/mcae037.
Niche differentiation is a crucial issue in speciation. Although it has a well-known role in adaptive processes of hybrid angiosperms, it is less understood in hybrid ferns. Here, we investigate whether an intermediate ecological niche of a fern hybrid is a novel adaptation that provides insights into fern hybrid speciation.
Pteris fauriei (Pteridaceae) is a natural hybrid fern, occurring in environments between its parent species. The maternal Pteris minor is found in sunny areas, but the habitat of the paternal Pteris latipinna is shady. We combined data from morphology, leaf anatomy and photosynthetic traits to explore adaptation and differentiation, along with measuring the environmental features of their niches. We also performed experiments in a common garden to understand ecological plasticity.
The hybrid P. fauriei was intermediate between the parent species in stomatal density, leaf anatomical features and photosynthetic characteristics in both natural habitats and a common garden. Interestingly, the maternal P. minor showed significant environmental plasticity and was more similar to the hybrid P. fauriei in the common garden, suggesting that the maternal species experiences stress in its natural habitats but thrives in environments similar to those of the hybrid.
Based on the similar niche preferences of the hybrid and parents, we propose hybrid superiority. Our results indicate that the hybrid P. fauriei exhibits greater fitness and can compete with and occupy the initial niches of the maternal P. minor. Consequently, we suggest that the maternal P. minor has experienced a niche shift, elucidating the pattern of niche differentiation in this hybrid group. These findings offer a potential explanation for the frequent occurrence of hybridization in ferns and provide new insights into fern hybrid speciation, enhancing our understanding of fern diversity.
生态位分化是物种形成过程中的一个关键问题。虽然它在杂交被子植物的适应过程中起着众所周知的作用，但在杂交蕨类植物中却知之甚少。在这里，我们研究蕨类植物杂种的中间生态位是否是一种新的适应，从而为蕨类植物杂种的形成提供了新的认识。
凤尾蕨（凤尾蕨科）是一种自然杂交蕨类植物，存在于其亲代物种之间的环境中。其母本细叶凤尾蕨分布在阳光充足的地区，而父本阔鳞凤尾蕨的栖息地则较为阴凉。我们结合形态学、叶片解剖学和光合作用特征的数据，来探索适应和分化，并测量其生态位的环境特征。我们还在一个普通花园中进行了实验，以了解生态可塑性。
杂交凤尾蕨在自然生境和普通花园中，在气孔密度、叶片解剖特征和光合作用特征方面都介于双亲之间。有趣的是，母本细叶凤尾蕨表现出明显的环境可塑性，在普通花园中与杂交凤尾蕨更为相似，这表明母本在其自然生境中受到压力，但在类似于杂种的环境中茁壮成长。
基于杂种和双亲对相似生态位的偏好，我们提出了杂种优势假说。我们的结果表明，杂交凤尾蕨表现出更高的适应性，可以与母本细叶凤尾蕨竞争并占据其初始生态位。因此，我们认为母本细叶凤尾蕨经历了生态位转移，阐明了该杂交群体中生态位分化的模式。这些发现为蕨类植物中频繁发生的杂交现象提供了潜在的解释，并为蕨类植物杂种的形成提供了新的认识，增强了我们对蕨类植物多样性的理解。
