早期发散被子植物番荔枝科关键功能花卉性状的演化,Journal of Systematics and Evolution

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早期发散被子植物番荔枝科关键功能花卉性状的演化
Journal of Systematics and Evolution ( IF 3.4 ) Pub Date : 2020-07-01 , DOI: 10.1111/jse.12645
Richard M. K. Saunders ₁

Affiliation

在物种丰富的早期发散被子植物番荔枝科中评估了潜在的关键功能花卉性状。传粉者（通常是甲虫）被各种线索（特别是视觉、嗅觉和产热）吸引，传粉者在部分封闭的花室内获得花蜜（通常为柱头渗出液）、热量和保护。花瓣有时充当传粉者的繁殖场所，尽管这可能具有欺骗性。番荔枝科物种是自交亲和的，异交由原型、雌雄同体、花同步和二期的组合促进。花粉聚集、花期持续时间的变化和传粉媒介捕获（涉及花瓣运动和传粉媒介的昼夜节律之间的紧密对齐）提高了授粉效率。大多数番荔枝科的花是露头的，同心性仅限于极少数谱系；因此，通过花粉管的心皮间生长优化受精，通过柱头渗出液（上雌蕊外层）或可能的花托（下层雌外层）。虽然番荔枝科缺乏独特的花柱，但几个谱系的柱头被拉长形成“假花柱”，被认为是花粉竞争的场所。花可被视为胚珠尚未受精的未成熟果实，其花性状在开花期间可能几乎没有选择优势，理论上可促进果实和种子的传播。番荔枝科花卉可能延续了拟真果树的特性，因为它促进了单果树的独立扩散（来自不同的心皮），从而最大化幼苗之间的空间/时间距离。这可能会弥补由于花粉供体的多样性有限而导致果实内种子之间缺乏遗传多样性的问题。

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The evolution of key functional floral traits in the early divergent angiosperm family Annonaceae

Potential key functional floral traits are assessed in the species‐rich early divergent angiosperm family Annonaceae. Pollinators (generally beetles) are attracted by various cues (particularly visual, olfactory, and thermogenic), with pollinators rewarded by nectar (generally as stigmatic exudate), heat, and protection within the partially enclosed floral chamber. Petals sometimes function as pollinator brood sites, although this could be deceptive. Annonaceae species are self‐compatible, with outcrossing promoted by a combination of protogyny, herkogamy, floral synchrony, and dicliny. Pollination efficiency is enhanced by pollen aggregation, changes in anthesis duration, and pollinator trapping involving a close alignment between petal movements and the circadian rhythms of pollinators. Most Annonaceae flowers are apocarpous, with syncarpy restricted to very few lineages; fertilization is therefore optimized by intercarpellary growth of pollen tubes, either by stigmatic exudate (suprastylar extragynoecial compitum) or possibly the floral receptacle (infrastylar extragynoecial compitum). Although Annonaceae lack a distinct style, the stigmas in several lineages are elongated to form “pseudostyles” that are hypothesized to function as sites for pollen competition. Flowers can be regarded as immature fruits in which the ovules are yet to be fertilized, with floral traits that may have little selective advantage during anthesis theoretically promoting fruit and seed dispersal. The plesiomorphic apocarpous trait may have been perpetuated in Annonaceae flowers as it promotes the independent dispersal of fruit monocarps (derived from separate carpels), thereby maximizing the spatial/temporal distance between seedlings. This might compensate for the lack of genetic diversity among seeds within fruits arising from the limited diversity of pollen donors.

更新日期：2020-07-01

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