Environmental Studies Program, University of Colorado, Boulder, Colorado, 80302, USA.
Biology Department, Appalachian State University, Boone, North Carolina, 28608, USA.
Ecology. 2019 Apr;100(4):e02639. doi: 10.1002/ecy.2639. Epub 2019 Mar 11.
Population-wide outcomes such as abundance, reproductive output, or mean survival can be stabilized by non-synchronous variation in the performance of individuals or subpopulations. Such "portfolio effects" have been increasingly documented at the scale of subpopulations and are thought to play an important role in generating stability of population phenomena in the face of environmental variation. However, few studies quantify the strength and origin of portfolio effects at the finer scale of individuals. We used 16 yr of fruit production and climate data for an alpine plant to dissect the scale of portfolio effects in reproduction, as well as the contribution of individual traits including size and flowering time in driving reproductive output. Asynchrony in reproductive success substantially reduces variation in population-level reproductive output, with approximately one-fourth of this stabilizing effect arising from individual differences, mostly not those characterized by measured traits, and approximately three-fourths from asynchrony across subpopulations. These results emphasize the different scales and causes of portfolio effects. The decomposition for portfolio effects we provide can facilitate similar breakdowns of the strength and causes of these effects in other systems.
人口的广泛结果，如丰度、生殖输出或平均存活，可以通过个体或亚种群表现的非同步变化来稳定。这种“投资组合效应”在亚种群规模上得到了越来越多的记录，被认为在面对环境变化时对产生种群现象的稳定性起着重要作用。然而，很少有研究在个体更精细的尺度上量化投资组合效应的强度和来源。我们使用了 16 年的高山植物的果实产量和气候数据，来剖析繁殖中的投资组合效应的规模，以及包括大小和开花时间在内的个体特征在驱动生殖输出方面的贡献。生殖成功的异步性大大降低了种群水平生殖输出的变异性，其中约四分之一的稳定作用来自个体差异，主要不是那些由测量特征来区分的个体差异，而大约四分之三的稳定作用来自亚种群间的异步性。这些结果强调了投资组合效应的不同尺度和原因。我们提供的投资组合效应分解可以促进在其他系统中对这些效应的强度和原因进行类似的细分。
