Department of Biosciences, Program in Ecology and Evolutionary Biology, Rice University, 6100 Main Street, MS-170, Houston, Texas, 77005-1892, USA.
Ecology. 2019 Nov;100(11):e02826. doi: 10.1002/ecy.2826. Epub 2019 Aug 14.
Climate change-induced phenological shifts are ubiquitous and have the potential to disrupt natural communities by changing the timing of species interactions. Shifts in first and/or mean phenological date are well documented, but recent studies indicate that shifts in synchrony (individual variation around these metrics) can be just as common. However, we know little about how both types of phenological shifts interact to affect species interactions and communities. Here, we experimentally manipulated the hatching phenologies of two competing species of larval amphibians to address this conceptual gap. Specifically, we manipulated the relative mean hatching time (early, same, or late relative to competitor) and population synchrony (high, medium, or low levels of variation around the mean) in a full 3 × 3 factorial design to measure independent and interactive effects of phenological mean and population phenological synchrony on competitive outcomes. Our results indicate that phenological synchrony within a population strongly influences intraspecific competition by changing the density of individuals and relative strength of early- vs. late-arriving individuals. Individuals from high-synchrony populations competed symmetrically, whereas individuals from low-synchrony populations competed asymmetrically. At the community scale, shifts in population phenological synchrony interact with shifts in phenological mean to affect key demographic rates (survival, biomass export, per capita mass, and emergence timing) strongly. Furthermore, changes in mean timing of species interactions altered phenological synchrony within a population at the next life stage, and phenological synchrony at one life stage altered the mean timing of the next life stage. Thus, shifts in phenological synchrony within populations cannot only alter species interactions, but species interactions in turn can also drive shifts in phenology.
气候变化引起的物候变化普遍存在，通过改变物种相互作用的时间，有可能破坏自然群落。物候期的最早和/或平均日期的变化已经有充分的记录，但最近的研究表明，同步性（围绕这些指标的个体变异）的变化也可能同样常见。然而，我们对这两种物候变化如何相互作用影响物种相互作用和群落知之甚少。在这里，我们通过实验操纵两种竞争的幼体两栖动物的孵化物候来解决这一概念上的差距。具体来说，我们在完全的 3×3 析因设计中操纵相对平均孵化时间（早、同、晚相对于竞争者）和种群同步性（围绕平均值的高、中、低水平变异），以测量物候平均和种群物候同步性对竞争结果的独立和交互影响。我们的结果表明，种群内的物候同步性通过改变个体密度和早到与晚到个体的相对强度，强烈影响种内竞争。来自高同步种群的个体进行对称竞争，而来自低同步种群的个体进行不对称竞争。在群落尺度上，种群物候同步性的变化与物候平均的变化相互作用，强烈影响关键的人口率（存活率、生物量输出、人均质量和出现时间）。此外，物种相互作用的平均时间变化在下一个生命阶段改变了种群内的物候同步性，而一个生命阶段的物候同步性改变了下一个生命阶段的平均时间。因此，种群内物候同步性的变化不仅可以改变物种相互作用，而且物种相互作用反过来也可以驱动物候的变化。
