Changing Climate Drives Divergent and Nonlinear Shifts in Flowering Phenology across Elevations

First author: Nicole E. Rafferty; Affiliations: University of California, Riverside (加利福尼亚大学河滨分校): Riverside, USA

Corresponding author: Nicole E. Rafferty

Climate change is known to affect regional weather patterns and phenology (物候); however, we lack understanding of how climate drives phenological change across local spatial gradients. This spatial variation is critical for determining whether subpopulations and metacommunities are changing in unison or diverging in phenology. Divergent responses could reduce synchrony both within species (disrupting gene flow among subpopulations) and among species (disrupting interspecific interactions in communities). We also lack understanding of phenological change in environments where life history events are frequently aseasonal, such as the tropical, arid, and semi-arid ecosystems that cover vast areas. Using a 33-year-long dataset spanning a 1,267-m semi-arid elevational gradient in the southwestern United States, we test whether flowering phenology diverged among subpopulations within species and among five communities comprising 590 species. Applying circular statistics to test for changes in year-round flowering, we show flowering has become earlier for all communities except at the highest elevations. However, flowering times shifted at different rates across elevations likely because of elevation-specific changes in temperature and precipitation, indicating diverging phenologies of neighboring communities. Subpopulations of individual species also diverged at mid-elevation but converged in phenology at high elevation. These changes in flowering phenology among communities and subpopulations are undetectable when data are pooled across the gradient. Furthermore, we show that nonlinear changes in flowering times over the 33-year record are obscured by traditional calculations of long-term trends. These findings reveal greater spatiotemporal complexity in phenological responses than previously recognized and indicate climate is driving phenological reshuffling across local spatial gradients.

气候变化能够影响地区的天气模式以及物候，然而，目前对于气候是如何驱动不同地区空间梯度上的物候变化还不清楚。空间变化对于决定亚群和元群落的物候是一致变化还是分化是至关重要的。不同的响应可能会降低物种内部（破坏不同亚群之间的基因流）和物种之间（破坏群落内不同物种间的相互作用）的同步性。同时，我们对于生活史事件频繁发生季节变化的环境下物候变化的理解还有所缺乏，例如覆盖广阔区域的热带，干旱和半干旱生态系统。基于33年对于美国西南部横跨1267米海拔梯度的半干旱地区的数据，作者测试了同一物种内不同亚群及包含590个物种构成的五个群落之间是否存在开花物候的分化。通过圈图统计测试不同年份区间开花时间的变化，作者发现除了高海拔地区外，所有地区的开花都变得比以前更早了。但是，不同的海拔下开花时间的变化速率不太一致，有可能是海拔特异性的温度和降水变化所导致，显示了临近群落之间的物候分化。单个物种的不同亚群在中间海拔高度时物候存在分化，但在高海拔时则趋同。当作者将不同梯度收集的数据混和时，检测不到不同群落或不同亚群之间的物候变化。此外，作者还发现传统长期趋势估算会掩盖开花时间的非线性变化。本文的发现揭示了物候响应的时空复杂性要比之前所认为的更加复杂，并且揭示了气候驱动了不同地区在空间梯度上物候变化。

通讯：Nicole E. Rafferty (https://profiles.ucr.edu/app/home/profile/rafferty)

个人简介：2011年，威斯康星大学麦迪逊分校，博士。

研究方向：由气候变化诱导的物候和分布变化对于物种之间相互关系的影响。

doi: https://doi.org/10.1016/j.cub.2019.11.071

Journal: Current Biology

Published date: January 02, 2020