East Carolina University, Department of Biology, Howell Science Building, Greenville, NC, 27858.
Southeast Missouri State University, Department of Biology, One University Plaza, MS 6200, Cape Girardeau, MO, 63701.
Am J Bot. 2018 Apr;105(4):641-655. doi: 10.1002/ajb2.1045. Epub 2018 Apr 6.
In a seminal body of theory, Lloyd showed that the fitness consequences of selfing will depend on its timing in anthesis. Selfing that occurs after opportunities for outcrossing or pollen dispersal can provide reproductive assurance when pollinators are limited and is expected to incur little cost, even when inbreeding depression is high. As a result, delayed selfing is often interpreted as a "best-of-both-worlds" mating system that combines the advantages of selfing and outcrossing.
We surveyed 65 empirical studies of delayed selfing, recording floral mechanisms and examining information on inbreeding depression, autofertility, and other parameters to test the support for delayed selfing as a best-of-both-worlds strategy.
Phylogenetic distribution of the diverse floral mechanisms suggests that some basic floral structures may predispose plant taxa to evolve delayed selfing. Delayed selfing appears to serve as a best-of-both-worlds strategy in some but not all species. While the capacity for autonomous selfing is often high, it is lower, in some cases, than in related species with earlier modes of selfing. In other delayed-selfers, low inbreeding depression and reduced investment in corollas and pollen suggest limited benefits from outcrossing.
Despite a growing literature on the subject, experimental evidence for delayed selfing is limited and major gaps in knowledge remain, particularly with respect to the stability of delayed selfing and the conditions that may favor transitions between delayed and earlier selfing. Finally, we suggest a potential role of delayed selfing in facilitating transitions from self-incompatibility to selfing.
在一个重要的理论体系中，劳埃德表明自交的适合度后果将取决于其在花期的时间。在有机会进行异交或花粉传播之后发生的自交，当传粉者受到限制时，可以提供繁殖保障，并且预计即使自交衰退率很高，也不会产生太大的成本。因此，延迟自交通常被解释为一种“两全其美”的交配系统，它结合了自交和异交的优势。
我们调查了 65 项关于延迟自交的实证研究，记录了花卉机制，并检查了关于自交衰退、自交亲和性和其他参数的信息，以检验延迟自交作为一种“两全其美”策略的支持。
各种花卉机制的系统发育分布表明，某些基本的花卉结构可能使植物类群更容易进化出延迟自交。延迟自交似乎在某些但不是所有物种中充当“两全其美”的策略。虽然自主自交的能力通常很高，但在某些情况下，它比具有较早自交模式的相关物种要低。在其他延迟自交者中，自交衰退率较低，以及对花冠和花粉的投资减少，表明从异交中获得的收益有限。
尽管关于这个主题的文献越来越多，但延迟自交的实验证据仍然有限，并且仍然存在重大的知识差距，特别是关于延迟自交的稳定性以及可能有利于延迟自交和更早自交之间转变的条件。最后，我们提出了延迟自交在促进从自交不亲和到自交的转变中的潜在作用。
