Adler Peter B, HilleRisLambers Janneke, Kyriakidis Phaedon C, Guan Qingfeng, Levine Jonathan M
Department of Wildland Resources and the Ecology Center, 5230 Old Main Hill, Utah State University, Logan, UT 83422, USA.
Proc Natl Acad Sci U S A. 2006 Aug 22;103(34):12793-8. doi: 10.1073/pnas.0600599103. Epub 2006 Aug 14.
How expected increases in climate variability will affect species diversity depends on the role of such variability in regulating the coexistence of competing species. Despite theory linking temporal environmental fluctuations with the maintenance of diversity, the importance of climate variability for stabilizing coexistence remains unknown because of a lack of appropriate long-term observations. Here, we analyze three decades of demographic data from a Kansas prairie to demonstrate that interannual climate variability promotes the coexistence of three common grass species. Specifically, we show that (i) the dynamics of the three species satisfy all requirements of "storage effect" theory based on recruitment variability with overlapping generations, (ii) climate variables are correlated with interannual variation in species performance, and (iii) temporal variability increases low-density growth rates, buffering these species against competitive exclusion. Given that environmental fluctuations are ubiquitous in natural systems, our results suggest that coexistence based on the storage effect may be underappreciated and could provide an important alternative to recent neutral theories of diversity. Field evidence for positive effects of variability on coexistence also emphasizes the need to consider changes in both climate means and variances when forecasting the effects of global change on species diversity.
气候变率的预期增加将如何影响物种多样性，取决于这种变率在调节竞争物种共存中所起的作用。尽管有理论将时间性环境波动与多样性的维持联系起来，但由于缺乏适当的长期观测，气候变率对稳定共存的重要性仍然未知。在此，我们分析了来自堪萨斯草原三十年的种群统计学数据，以证明年际气候变率促进了三种常见草种的共存。具体而言，我们表明：（i）这三个物种的动态满足基于具有重叠世代的补充变率的“存储效应”理论的所有要求；（ii）气候变量与物种表现的年际变化相关；（iii）时间变率增加了低密度生长率，使这些物种免受竞争排斥。鉴于环境波动在自然系统中普遍存在，我们的结果表明基于存储效应的共存可能未得到充分认识，并且可能为近期的中性多样性理论提供重要的替代解释。变率对共存产生积极影响的实地证据还强调，在预测全球变化对物种多样性的影响时，需要考虑气候均值和方差的变化。
