Diversity and evolution of the gynoecium in Cuscuta (dodders, Convolvulaceae) in relation to their reproductive biology: two styles are better than one
Diversity and evolution of the gynoecium in Cuscuta (dodders, Convolvulaceae) in relation to their reproductive biology: two styles are better than one
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菟丝子（菟丝子、旋花科）雌蕊的多样性和进化与其生殖生物学的关系：两种风格优于一种风格
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发表时间：
2011
影响因子：
1.9
通讯作者：
M. Costea
中科院分区：
文献类型：
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作者：
Michael A. R. Wright;M. Welsh;M. Costea
利用光学显微镜和扫描电镜对菟丝子属122种14变种的雌蕊群进行了研究，以评估其多样性和进化，并为了解该属中不同的生殖策略提供形态学基础。根据核ITS和质体trnL-F序列，将数据优化到由该属的三个大规模分子遗传学构建的共识树中。花柱的数量和柱头的形状是唯一能区分菟丝子亚属的花/果特征。此外，雌蕊群的形态是有用的界定物种在一些分支。亚属的单花柱雌蕊群。Monogynella很可能是祖先，而具有两种风格的雌蕊花则来自于Cuscuta和Grammica亚属。雌蕊花有两种风格，在后面的亚属中遇到提供了一个更大的形态复杂性和灵活性的各种生殖策略。在subg.在菟丝子属中，花开放后，花柱和柱头都继续伸长并改变位置，直到授粉发生。在subg. Grammica，两个不等的风格可能会导致空间分离的性别在花，herkogamy，而两个柱头成熟顺序，并有不同的时间，他们的受粉。蜜腺由子房基部的一圈改良气孔组成，相当于许多旋花科中存在的下位蜜腺盘，在所有菟丝子属物种中首次观察到。花柱的脉管系统减少，主要由韧皮部代表;木质部仅存在于亚木质部中。单雌虫雌蕊的乳突直径、柱头表面积、柱头宽度、花柱宽度等性状与花粉量、花粉极赤道比、顶盖穿孔等性状呈中度相关。雌蕊群的特征表明菟丝子属与旋花科中的“双枝分支”（Dicranostyloideae）有亲缘关系。
The gynoecium of 122 species and 14 varieties of Cuscuta (dodders) was investigated by light and scanning electron microscopy to assess its diversity and evolution and to provide a morphological foundation for understanding the different reproductive strategies encountered in the genus. Data were optimized into a consensus tree constructed from three large-scale molecular phylogenies of the genus based on nuclear ITS and plastid trnL-F sequences. The number of styles combined with the stigma shape are the only floral/fruit characters that enable the separation of Cuscuta subgenera. In addition, gynoecium morphology is useful for delimiting species in some clades. The one-style gynoecium of subg. Monogynella is mostly likely ancestral whereas gynoecia with two styles are derived in subgenera Cuscuta and Grammica. Gynoecia with two styles encountered in the latter subgenera provide a greater morphological complexity and flexibility for various reproductive strategies. In subg. Cuscuta, both the equal styles and stigmas continue to elongate and modify their position after the flowers open, until pollination occurs. In subg. Grammica, the two unequal styles may cause a spatial separation of the sexes in the flower, herkogamy, while the two stigmas mature sequentially and have a differential timing of their receptivity for pollen. A nectary consisting of a ring of modified stomata at the base of the ovary, the equivalent of the hypogynous nectary disc present in many Convolvulaceae, was observed for the first time in all Cuscuta species. The vasculature of the styles is reduced, represented mostly by phloem; xylem is present only in subg. Monogynella. Some gynoecial characters, for example papillae diameter, stigma surface area, stigma width, and style width were moderately correlated with pollen volume, pollen polar–equatorial ratio and tectum perforation. Gynoecium features suggest that Cuscuta is allied with the “bifid clade” (Dicranostyloideae) in Convolvulaceae.