Gynodioecy or leaky dioecy? The unusual sexual system of a coral dune-habitant Tournefortia argentea (Boraginaceae)
Gynodioecy or leaky dioecy? The unusual sexual system of a coral dune-habitant Tournefortia argentea (Boraginaceae)
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DOI：
10.1007/s00606-020-01698-0
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发表时间：
2020-07
影响因子：
1.9
通讯作者：
Xiangping Wang;Meihong Wen;Ming-Jou Wu;Yuanqing Xu;Kai-Hong Zhang;Dianxiang Zhang
中科院分区：
文献类型：
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作者：
Xiangping Wang;Meihong Wen;Ming-Jou Wu;Yuanqing Xu;Kai-Hong Zhang;Dianxiang Zhang
银合欢（Tournefortia argentea）是印度-太平洋沿岸的一种草本植物，其独特的有性系统至今仍不清楚。在这里，我们研究了T. argentebased上的形态和微形态研究，以及操纵授粉处理。西沙群岛自然种群中存在两性植物和雌性植物两种类型。每一个有性形态都表现出不同的花特征，表现出适度的两性异形。两性花的花冠和花药明显大于雌花。自然坐果率和人工授粉坐果率均远低于雌株，表现出渗漏型雌雄异株特征。我们调查了这些差异在花性状之间的女性和雌雄同体影响传粉者的选择。虽然雌花和两性花在T. argentea吸引了相同的传粉者物种，包括蜜蜂，Syrphidae和Utetheisa loyaldae（Arctiidae）的组合，减少分配到传粉者吸引结构（花冠）和奖励产品导致蜜蜂科访问雌花显着减少。因此，T. argenteis是紫草科开花植物中雌蕊异株物种的另一个例子，具有明显的两性二型性，发生在海洋岛屿上。银汉木的性系统可能意味着在进化到雌雄异株的过渡阶段，并且可能在殖民到新开垦的栖息地期间受到青睐，在那里交配伴侣可能有限。
The high occurrence of dioecy on oceanic islands has attracted much attention from plant evolutionary biologists.Tournefortia argentea(Boraginaceae), an Indo-Pacific strand plant, has an unusual sexual system which remains poorly understood. Here, we investigated the sexual system ofT. argenteabased on morphological and micromorphological studies, as well as manipulated pollination treatments. Two morphs of plants were found in the natural populations on Xisha Islands: hermaphrodite and female plants. Each sexual morph exhibited different floral traits, showing a modest form of sexual dimorphism. Flowers of hermaphrodites display significantly larger size in corolla and anther than those of females. Fruit sets under natural condition and hand pollination in hermaphroditic individuals were both far lower than that of female ones, which shows characteristics of both leaky dioecy and gynodioecy. We investigated how these differences in floral traits between females and hermaphrodites affect the choice of pollinators. Although females and hermaphroditic flowers inT. argenteaattracted the same assemblage of pollinator species, including Apidae, Syrphidae andUtetheisa lotrix(Arctiidae), the reduction in allocation to pollinator-attracting structures (corolla) and rewarding products caused a significant reduction in Apidae visitation to female flowers. Accordingly,T. argenteais another example of a gynodioecious species of flowering plants in Boraginaceae with clear sexual dimorphism occurring in oceanic islands. The sexual system inT. argenteamay imply a transitional stage in the evolution to dioecy and may have been favored during colonization to newly reclaimed habitats, where mating partners may be limited.