PREMISE Understanding how environmental stress affects the strength of mutualisms is critically important given observed and projected environmental changes. In particular, the frequency and duration of drought have been increasing worldwide. We investigated how water availability affects plant traits that mediate a pollination mutualism. METHODS For butterfly-pollinated Phlox drummondii, we determined how moisture availability affects flower size, nectar volume, and nectar sugar amount. Furthermore, we explored the role that local adaptation may play in responses to moisture availability by including plants collected from regions that differ in aridity. Finally, we determined whether responses of plant populations to selection may differ under drought by calculating heritability of traits under control and dry conditions. RESULTS Flower size was generally smaller in dry plants than in control plants. Early in the treatment period, nectar volume and sugar were higher in dry plants than in control plants for plants from both arid and wetter regions. With prolonged dry treatment, nectar volume and sugar remained higher only in plants from the arid region. Heritability of floral traits was lower for water-limited plants than for control plants. CONCLUSIONS Plant investment into pollination mutualisms under environmental stress may depend on the extent to which populations are already locally adapted to such conditions, suggesting that mutualism may remain strong, at least in arid regions. However, decreases in heritability under water-limitation suggest that responses to selection imposed by pollinators may be low, even if drought-adapted plants maintain production of rewards to pollinators.

中文翻译：

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局部适应介导一年生野花对水分限制的花卉反应

前提 考虑到观察到和预测的环境变化，了解环境压力如何影响共生关系的强度至关重要。特别是，世界范围内干旱的频率和持续时间都在增加。我们调查了水的可用性如何影响介导授粉互惠的植物性状。方法对于蝴蝶授粉的福禄考，我们确定了水分可用性如何影响花朵大小、花蜜量和花蜜糖量。此外，我们通过包括从不同干旱地区收集的植物，探讨了局部适应在响应水分可用性方面可能发挥的作用。最后，我们通过计算控制和干燥条件下性状的遗传力来确定植物种群对选择的反应在干旱下是否可能不同。结果 干燥植物的花大小通常比对照植物小。在处理早期，对于来自干旱和湿润地区的植物，干燥植物的花蜜量和糖分高于对照植物。随着干燥处理时间延长，只有干旱地区植物的花蜜量和糖分保持较高。限水植物的花卉性状遗传力低于对照植物。结论 植物在环境压力下对授粉互惠的投资可能取决于种群在当地适应这种条件的程度，这表明互惠可能仍然很强，至少在干旱地区。然而，在限水条件下遗传力的下降表明对传粉媒介施加的选择的反应可能很低，