Changes in phenology are a conspicuous fingerprint of climate change, leading to fears that phenological mismatches among interacting species will be a leading cause of population declines and extinction. We used quantile regression to analyze museum collection data and estimate changes in the phenological overlap of Baltimore checkerspot butterflies and 12 common nectar plant species over several decades in two geographic regions. We combined these museum data with field estimates of each species' flower density and nectar sugar production to estimate changes in resource availability caused by shifts in phenological overlap. Phenological overlap (measured as the proportion of plant flowering during the flight period of an average butterfly) decreased through time, primarily because the flowering period of nectar plants was longer, but the flight period of butterflies was shorter in recent years. Our study was also motivated by the hypothesis that phenological mismatches may be more severe in the southern region due to a midsummer dearth in floral resources, but this hypothesis was not supported by our data. Although phenological overlap was somewhat smaller in the southern region, changes in overlap through time were similar in both regions. When phenological overlap was weighted by nectar sugar production of different species, the overlap increased in the southern region but decreased in the northern region (the opposite of our prediction). Overall, nectar resources were much more abundant at study sites in our northern region than in our southern region, possibly due to differences in land management. Our study demonstrates the complexities of phenological mismatch of interacting species and highlights that phenological changes may have small impacts on population viability.

中文翻译：

---

对于方格斑蝶来说，物候不匹配不如花蜜总可用性重要


物候的变化是气候变化的一个明显指纹，导致人们担心相互作用的物种之间的物候不匹配将成为种群数量下降和灭绝的主要原因。我们使用分位数回归来分析博物馆收藏数据，并估计两个地理区域几十年来巴尔的摩方格斑蝶和 12 种常见花蜜植物物种的物候重叠变化。我们将这些博物馆数据与每个物种的花密度和花蜜糖产量的实地估计相结合，以估计物候重叠变化引起的资源可用性变化。物候重叠（以普通蝴蝶飞行期间植物开花的比例衡量）随着时间的推移而减少，主要是因为花蜜植物的开花时间较长，但近年来蝴蝶的飞行期较短。我们的研究还受到这样一个假设的推动，即由于盛夏花卉资源匮乏，南部地区的物候错配可能更严重，但这一假设没有得到我们的数据支持。尽管南部地区的物候重叠略小，但两个地区的重叠随时间的变化相似。当物候重叠按不同物种的花蜜糖产量加权时，重叠在南部地区增加，而在北部地区减少（与我们的预测相反）。总体而言，我们北部地区的研究地点的花蜜资源比我们南部地区丰富得多，这可能是由于土地管理的差异。 我们的研究证明了相互作用物种物候不匹配的复杂性，并强调物候变化可能对种群生存能力产生很小的影响。