Grillo Michael, Gutiérrez Andrés
Department of Biology, Loyola University Chicago 1032 W. Sheridan Rd. Chicago, IL 60660, United States.
AoB Plants. 2024 Dec 31;17(1):plae073. doi: 10.1093/aobpla/plae073. eCollection 2025 Jan.
The shift from outcrossing to predominantly selfing is one of the most common transitions in plant evolution. This evolutionary shift has received considerable attention from biologists; however, this work has almost exclusively been focused on animal-pollinated systems. Despite the seminal ecological and economic importance of wind-pollinated species, the mechanisms controlling the degree of outcrossing in wind-pollinated taxa remain poorly understood. As a first step toward addressing this issue, we have conducted a comparative study of floral biology between two recently diverged sister species, and (Poaceae), that are wind-pollinated and possess distinct mating systems with being outcrossing and highly self-fertilized Therefore, these species present an ideal system for exploring mating system evolution in wind-pollinated taxa. We have identified key floral traits that differ between populations of these species and that are associated with mating system divergence including anther length, anther basal pore size, stigma papillae density, panicle shape, panicle exsertion, pollen viability, and early anther dehiscence. Of these traits, large anther basal pore size and early anther dehiscence are hypothesized to confer reliable autogamous selfing in . Manipulations of floret number were conducted to partition the role of geitonogamy and autogamy in conferring self-fertilization. This experiment revealed that selfing in is consistent with autogamous selfing, whereas achieves selfing through geitonogamy. This study serves as a model for understanding the floral mechanisms controlling the outcrossing rate in other wind-pollinated systems, most notably other grasses.
从异交为主转变为主要自交是植物进化中最常见的转变之一。这种进化转变受到了生物学家的广泛关注；然而，这项工作几乎完全集中在动物传粉系统上。尽管风媒传粉物种具有重要的生态学和经济意义，但控制风媒传粉类群异交程度的机制仍知之甚少。作为解决这一问题的第一步，我们对两个最近分化的姊妹物种——[物种名1]和[物种名2]（禾本科）进行了花生物学的比较研究，它们都是风媒传粉的，并且具有不同的交配系统，[物种名1]为异交，[物种名2]高度自花受精。因此，这些物种为探索风媒传粉类群的交配系统进化提供了一个理想的系统。我们已经确定了这些物种种群之间不同且与交配系统分化相关的关键花部性状，包括花药长度、花药基部孔径、柱头乳突密度、圆锥花序形状、圆锥花序伸出度、花粉活力和花药早期开裂。在这些性状中，大的花药基部孔径和花药早期开裂被认为赋予了[物种名2]可靠的自花自交能力。通过对小花数量的操作来区分同株异花授粉和自花授粉在实现自花受精中的作用。该实验表明，[物种名2]的自交与自花自交一致，而[物种名1]则通过同株异花授粉实现自交。这项研究为理解控制其他风媒传粉系统，尤其是其他禾本科植物异交率的花部机制提供了一个模型。
