Spatiotemporal variation in natural selection is expected, but difficult to estimate. Pollinator-mediated selection on floral traits provides a good system for understanding and linking variation in selection to differences in ecological context. We studied pollinator-mediated selection in five populations of Dalechampia scandens (Euphorbiaceae) in Costa Rica and Mexico. Using a nonlinear path-analytical approach, we assessed several functional components of selection, and linked variation in pollinator-mediated selection across time and space to variation in pollinator assemblages. After correcting for estimation error, we detected moderate variation in net selection on two out of four blossom traits. Both the opportunity for selection and the mean strength of selection decreased with increasing reliability of cross-pollination. Selection for pollinator attraction was consistently positive and stronger on advertisement than reward traits. Selection on traits affecting pollen transfer from the pollinator to the stigmas was strong only when cross pollination was unreliable and there was a mismatch between pollinator and blossom size. These results illustrate how consideration of trait function and ecological context can facilitate both the detection and the causal understanding of spatiotemporal variation in natural selection. This article is protected by copyright. All rights reserved.

中文翻译：

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使用生态环境来解释自然选择的时空变化

自然选择的时空变化是可以预料的，但难以估计。传粉媒介介导的花卉性状选择提供了一个很好的系统，可以理解选择的变异并将其与生态环境的差异联系起来。我们在哥斯达黎加和墨西哥的五个大戟科（大戟科）种群中研究了传粉媒介介导的选择。使用非线性路径分析方法，我们评估了选择的几个功能组件，并将传粉媒介介导的选择跨时间和空间的变化与传粉媒介组合的变化联系起来。在校正估计误差后，我们在四个开花性状中的两个上检测到净选择的适度变化。选择机会和平均选择强度都随着异花授粉可靠性的增加而减少。对传粉媒介吸引力的选择在广告上始终是积极的，而且比奖励性状更强。只有当异花授粉不可靠并且传粉媒介和花朵大小不匹配时，才会对影响花粉从传粉媒介转移到柱头的性状进行选择。这些结果说明了对性状功能和生态环境的考虑如何促进对自然选择中时空变化的检测和因果理解。本文受版权保护。版权所有。这些结果说明了对性状功能和生态环境的考虑如何促进对自然选择中时空变化的检测和因果理解。本文受版权保护。版权所有。这些结果说明了对性状功能和生态环境的考虑如何促进对自然选择中时空变化的检测和因果理解。本文受版权保护。版权所有。