Biology Department, Franklin & Marshall College, Lancaster, 17604, USA.
Sci Rep. 2018 Dec 13;8(1):17802. doi: 10.1038/s41598-018-36152-2.
The consequences of altered flowering dates due to climate change can be severe, especially for plants that rely on coordinated flower and pollinator emergence for reproduction. The plant Asclepias syriaca (Common Milkweed) relies on pollinators for movement of its pollen and evidence suggests that it has recently been declining. Given these factors and this plant's importance as a host species for the declining Danaus plexippus (Monarch Butterfly), it is critical to determine if its flowering is being modified by climate change. As a first step to answering this question I quantified the relationship between climate and flowering date for A. syriaca using data from the USA National Phenology Network repository and the National Oceanic and Atmospheric Administration. I found that temperatures were higher than they had been historically (1895-2010) and mean flowering dates occurred earlier with higher temperatures. Additionally, there is a significant negative interactive effect of temperature and year on flowering date indicating that from 2011 through 2016 higher temperatures are correlated with increasingly earlier flowering dates. The change in flowering appears to be symmetrical in regards to the flowering time distribution, in that along with the mean, both maximum and minimum flowering dates are occurring earlier, as well. There is no evidence that earlier flowering is due to earlier initial growth or results in later fruit ripening. Consequences of this shift in flowering can only be speculated upon at this point, but due to the ecological importance of A. syriaca and its susceptibility to phenological mismatch, they should be considered when developing conservation plans for A. syriaca and the organisms for which it is a host.
由于气候变化导致花期改变的后果可能很严重，特别是对于那些依赖协调的花和传粉者出现进行繁殖的植物来说。植物 Asclepias syriaca（普通乳草）依赖传粉者来移动其花粉，有证据表明它最近正在减少。考虑到这些因素以及这种植物作为 Danaus plexippus（帝王蝶）这种数量减少的蝴蝶的宿主物种的重要性，确定其花期是否因气候变化而改变至关重要。作为回答这个问题的第一步，我使用来自美国国家物候网络数据库和美国国家海洋和大气管理局的数据来量化 Asclepias syriaca 的气候与花期之间的关系。我发现，温度比历史上（1895-2010 年）更高，随着温度的升高，平均开花日期更早。此外，温度和年份对开花日期有显著的负交互作用，这表明 2011 年至 2016 年，较高的温度与开花日期的提前呈正相关。开花的变化在开花时间分布方面似乎是对称的，因为除了平均值外，最大和最小开花日期也更早。没有证据表明较早的开花是由于较早的初始生长或导致果实较晚成熟。目前，只能推测这种开花时间变化的后果，但由于 Asclepias syriaca 的生态重要性及其对物候不匹配的敏感性，在制定保护 Asclepias syriaca 和其宿主的生物的保护计划时，应该考虑到这些后果。
