Selection on flowering time in plants is often mediated by multiple agents, including climatic conditions and the intensity of mutualistic and antagonistic interactions with animals. These selective agents can have both direct and indirect effects. For example, climate might not only influence phenotypic selection on flowering time directly by affecting plant physiology, but it can also alter selection indirectly by modifying the seasonal activity and relative timing of animals interacting with plants. We used 21 yr of data to identify the drivers of selection on flowering time in the perennial herb Lathyrus vernus, and to examine if antagonistic plant–animal interactions mediate effects of climate on selection. We examined the fitness consequences of vertebrate grazing and predispersal seed predation, and how these effects varied among years and among individuals within years. Although both antagonistic plant–animal interactions had important negative effects on plant fitness, only grazing intensity was consistently related to plant phenology, being higher in early-flowering individuals. Spring temperature influenced the intensity of both plant–animal interactions, as well as the covariance between seed predation and plant phenology. However, only differences in grazing intensity among years were associated with differences in selection on flowering time; the strength of selection for early flowering being stronger in years with lower mean intensity of grazing. Our results illustrate how climatic conditions can influence plant–animal interactions that are important selective agents for plant traits. A broader implication of our findings is that both ecological and evolutionary responses to climatic changes might be indirect, and largely mediated by species interactions.

中文翻译：

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植物-动物相互作用介导气候对开花时间选择的影响

植物开花时间的选择通常由多种因素介导，包括气候条件以及与动物的互利和拮抗相互作用的强度。这些选择性试剂可以同时具有直接和间接作用。例如，气候不仅可以通过影响植物生理学直接影响开花时间的表型选择，还可以通过改变动物与植物相互作用的季节性活动和相对时间来间接改变选择。我们使用 21 年的数据来确定多年生草本Lathyrus vernus中开花时间选择的驱动因素，并检查拮抗的植物-动物相互作用是否介导了气候对选择的影响。我们检查了脊椎动物放牧和预传播种子捕食的健康后果，以及这些影响如何在不同年份和不同个体之间变化。尽管两种拮抗的植物-动物相互作用对植物适应性都有重要的负面影响，但只有放牧强度始终与植物物候相关，在早期开花的个体中更高。春季温度影响植物-动物相互作用的强度，以及种子捕食和植物物候学之间的协方差。然而，只有年份间放牧强度的差异与开花时间选择的差异有关；平均放牧强度较低的年份对早花的选择强度较强。我们的结果说明了气候条件如何影响动植物相互作用，而动植物相互作用是植物性状的重要选择因子。我们的研究结果更广泛的含义是，对气候变化的生态和进化反应可能是间接的，并且主要由物种相互作用介导。