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科学网—Current Biology：有花植物中闭花受精的演化机制

花匠小妙招
2024-11-12 08:08

Repeated evolution of a reproductive polyphenism in plants is strongly associated with bilateral flower symmetry

第一作者：Simon Joly

第一单位：加拿大蒙特利尔植物园

通讯作者：Daniel J. Schoen

Abstract

非遗传多型性：Polyphenisms are a special type of phenotypic plasticity in which the products of development are not continuous but instead are separate and distinct phenotypes produced in the same genetic background.

闭花受精-概念：One of the most widespread polyphenisms in the flowering plants is cleistogamy, in which the same individual plant produces both open, cross-pollinated flowers as well as highly reduced and closed, self-pollinated (cleistogamous) flowers.

闭花受精-演化：Cleistogamy is not a rare evolutionary phenomenon. It has evolved independently at least 41 times. But what favors the evolution of cleistogamy is still largely unknown.

达尔文的假设-1：Darwin proposed a hypothesis that has never been properly tested. He observed that cleistogamy is more common in taxa with bilaterally symmetric (zygomorphic) flowers than in those with radially symmetric (actinomorphic) flowers.

达尔文的假设-2：Moreover, Darwin suggested that cleistogamous flowers help to ensure pollination, which he postulated is less certain in zygomorphic taxa that rely on more specialized groups of pollinators.

结果-1：Here, we combined the largest datasets on floral symmetry and cleistogamy and used phylogenetic approaches to show that cleistogamy is indeed disproportionately associated with zygomorphic flowers and that zygomorphic species are more likely to evolve cleistogamy than actinomorphic species.

结果-2：We also show that zygomorphic species are less capable of autonomous open-flower self-pollination (lower autofertility), suggesting that selection of cleistogamy via reproductive assurance in zygomorphic taxa could help account for Darwin’s observation.

结论：Our results provide support for the hypothesis that polyphenisms are favored when organisms encounter contrasting environments.

摘要

非遗传多型性（polyphenism）是表型可塑性的一种特殊类型，其发育结果是不连续的，在同一遗传背景下能够产生分离的、不同的表型。有花植物中最普遍的一种非遗传多型性就是闭花受精（cleistogamy），即同一株植物既有开放、异交授粉的花，也有高度退化的、封闭的自交授粉的花。闭花受精并不是一个罕见的演化现象。其在整个有花植物谱系中至少独立演化了41次。但是，驱动闭花受精演化的因素还是不清楚。达尔文曾提出一个假设，但是从未被证实过。他发现闭花受精在具有两侧对称花的植物中，要比在具有辐射对称花的植物中更加普遍。此外，达尔文还表示闭花受精能够保证授粉的成功率，这有助于具有左右对称花的植物保证生殖成功，因为这一类植物的授粉十分依赖于高度特化的传粉群。本文中，作者结合大范围的花对称性数据以及闭花受精现象，利用系统发育的方法揭示闭花受精确实与左右对称花呈现出不成比例的相关性，即左右对称花要比辐射对称花更多的演化出闭花受精这一性状。作者还发现左右对称花的物种自主开花自交授粉的能力较差，即自我繁殖能力更低，说明通过左右对称花植物中通过生殖保证来对闭花受精进行选择可以帮助解释达尔文的观察。本文的研究结果支持这样一个假设，即当生物体遭遇完全不同的环境时，闭花受精就会具有演化上的优势。

通讯作者