Reproductive Traits of Pteris cadieri and P. grevilleana in Taiwan: Implications for Their Hybrid Origin

由二形鳳尾蕨及翅柄鳳尾蕨的生殖特徵推論其雜交起源

趙怡姍(Yi-Shan Chao) ； 劉和義(Ho-Yih Liu) ； 黃曜謀(Yao-Moan Huang) ； 邱文良(Wen-Liang Chiou)

《Botanical Studies》 51卷2期 (2010/04) Pp. 209-216

摘要

二形鳳尾蕨具有明顯的形態變異，葉形由單回羽片至二回羽裂。由於其形態與翅柄鳳尾蕨成一連續變異，故過去研究認為二形鳳尾蕨是一個雜交種而翅柄鳳尾蕨為其親本之一，但並無提供進一步證據或反證。本篇研究以台灣產的二形鳳尾蕨與翅柄鳳尾蕨的生殖特徵，探討此雜交起源的假設。研究發現二形鳳尾蕨具二倍體與三倍體，翅柄鳳尾蕨為二倍體，但兩種均行無配生殖。兩種在生殖特徵相似：孢子形狀具變異（四面體形，圓形，豆形），孢子發芽率具變異，幼孢子體的第一片葉具有中脈，配子體具偶發的多胚現象。生殖特徵的研究結果支持二形鳳尾蕨與翅柄鳳尾蕨同為雜交起源，而建議重新考慮翅柄鳳尾蕨為二形鳳尾蕨親本的假說。此外，本篇為無配生殖蕨類具多胚性的首次報導。

關鍵字

無配生殖 ； 雜交 ； 形態變異 ； 多倍體 ； 二形鳳尾蕨 ； 翅柄鳳尾蕨

並列摘要

Pteris cadieri (Pteridaceae) exhibits significant morphological variation, its fronds range from simply pinnate to bipinnatifid. The morphological characteristics of P. cadieri and P. grevilleana vary along a continuum and suggest that P. cadieri is a hybrid species and P. grevilleana is a potential parent species. However, previous studies do not provide evidence to support or refute this hypothesis. To explore this hypothesis of hybrid origin, the reproductive biology of P. cadieri and P. grevilleana was studied in Taiwan. There were diploid and triploid P. cadieri, but P. grevilleana was diploid. All plants of both species were apogamous. In both species, spore shape varied (tetrahedral, globose, ellipsoidal) and germination rate varied, the first frond of some juvenile sporophytes had a midrib, and polyembryony occasionally occurred, the latter being the first report of polyembryony in apogmous ferns. Variation in spore number per sporangium, spore size and spore shape indicated abnormal sporogenesis. All these traits suggested that P. cadieri and P. grevilleana are of hybrid origins. However, the hypothesis that P. grevilleana is a parent of P. cadieri should be reconsidered.

並列關鍵字

Apogamy ； Hybridization ； Morphological variation ； Polyploids ； Pteris cadieri ； Pteris grevilleana