Ehrlén Johan, Münzbergová Zuzana
Department of Botany, Stockholm University, SE-106 91 Stockholm, Sweden.
Am Nat. 2009 Jun;173(6):819-30. doi: 10.1086/598492.
The timing of reproduction influences how organisms interact with the environment and can have important fitness effects. In plants, the evolution of flowering phenology is often interpreted as the response to selection from mutualists, although antagonistic interactions may also be important. We examined direct and indirect phenotypic selection on the start of flowering via mutualistic and antagonistic interactions in the perennial herb Lathyrus vernus over 7 years. Flowering start influenced seed set, predispersal seed predation, and risk of grazing. These effects were in opposed directions and partly influenced different components of fitness. Combining information about effects on fitness components with information about links between fitness components and average lifetime fitness, in terms of population growth rate, showed that earlier flowering was associated with higher lifetime fitness in all years. These relationships were, however, mediated largely by variation in flower number, and direct selection on first flowering date was more variable among years. We conclude that long-term studies correcting for indirect selection and environmental covariance are needed to understand selection on reproductive phenology and that demographic approaches are necessary to assess selection mediated by several agents and influencing several components of fitness.
繁殖时间会影响生物体与环境的相互作用方式，并可能产生重要的适合度效应。在植物中，开花物候的进化通常被解释为对互利共生者选择的响应，尽管拮抗相互作用可能也很重要。我们在7年时间里，通过多年生草本植物春巢菜中的互利共生和拮抗相互作用，研究了对开花起始的直接和间接表型选择。开花起始影响结实率、种子传播前的种子捕食以及放牧风险。这些影响方向相反，部分影响了适合度的不同组成部分。将关于对适合度组成部分的影响信息与关于适合度组成部分与平均寿命适合度（以种群增长率衡量）之间联系的信息相结合，结果表明，在所有年份中，较早开花都与较高的寿命适合度相关。然而，这些关系很大程度上是由花数量的变化介导的，对首次开花日期的直接选择在不同年份间变化更大。我们得出结论，需要进行长期研究以校正间接选择和环境协方差，从而理解对繁殖物候的选择，并且人口统计学方法对于评估由多种因素介导并影响适合度多个组成部分的选择是必要的。
