Kellogg Biological Station, Michigan State University, Hickory Corners, MI, 49060-9505, USA.
Department of Plant Biology, Michigan State University, East Lansing, MI, 48824-6406, USA.
Am J Bot. 2021 Jun;108(6):958-970. doi: 10.1002/ajb2.1684. Epub 2021 Jun 16.
Shifting phenology in response to climate is one mechanism that can promote population persistence and geographic spread; therefore, species with limited ability to phenologically track changing environmental conditions may be more susceptible to population declines. Alternatively, apparently nonresponding species may demonstrate divergent responses to multiple environmental conditions experienced across seasons.
Capitalizing on herbarium records from across the midwestern United States and on detailed botanical surveys documenting local extinctions over the past century, we investigated whether extirpated and extant taxa differ in their phenological responses to temperature and precipitation during winter and spring (during flowering and the growing season before flowering) or in the magnitude of their flowering time shift over the past century.
Although warmer temperatures across seasons advanced flowering, extirpated and extant species differed in the magnitude of their phenological responses to winter and spring warming. Extirpated species demonstrated inconsistent phenological responses to warmer spring temperatures, whereas extant species consistently advanced flowering in response to warmer spring temperatures. In contrast, extirpated species advanced flowering more than extant species in response to warmer winter temperatures. Greater spring precipitation tended to delay flowering for both extirpated and extant taxa. Finally, both extirpated and extant taxa delayed flowering over time.
This study highlights the importance of understanding phenological responses to seasonal warming and indicates that extirpated species may demonstrate more variable phenological responses to temperature than extant congeners, a finding consistent with the hypothesis that appropriate phenological responses may reduce species' likelihood of extinction.
为了应对气候变化而改变物候是促进种群生存和地理扩散的一种机制；因此，那些在物候上难以跟踪环境变化的物种可能更容易出现种群减少。或者，那些明显没有反应的物种可能对跨季节经历的多种环境条件表现出不同的反应。
利用美国中西部的标本馆记录和详细的植物学调查记录，我们调查了在过去一个世纪中灭绝和现存的分类群在冬季和春季（开花期和开花前的生长季节）对温度和降水的物候反应，以及它们在过去一个世纪中开花时间变化的幅度是否存在差异。
尽管整个季节的变暖会提前开花，但灭绝和现存物种对冬季和春季变暖的物候反应幅度不同。灭绝物种对春季变暖的物候反应不一致，而现存物种则一致地提前开花以应对春季变暖。相比之下，灭绝物种对冬季变暖的反应比现存物种更能促进开花。春季降水增加往往会延迟开花，无论是灭绝的还是现存的分类群。最后，灭绝和现存的分类群随着时间的推移都会延迟开花。
本研究强调了了解季节性变暖对物候的反应的重要性，并表明灭绝物种对温度的物候反应可能比现存同属种更具变异性，这一发现与适当的物候反应可能降低物种灭绝可能性的假设一致。
