Am Nat. 2021 Apr;197(4):405-414. doi: 10.1086/713066. Epub 2021 Feb 24.
AbstractEnvironmental fluctuations can mediate coexistence between competing species via the storage effect. This fluctuation-dependent coexistence mechanism requires three conditions: (i) there is a positive covariance between species responses to environmental conditions and the strength of competition, (ii) there are species-specific environmental responses, and (iii) species are less sensitive to competition in environmentally unfavorable years. In serially uncorrelated environments, condition (i) occurs only if favorable environmental conditions immediately and directly increase the strength of competition. For many demographic parameters, this direct link between favorable years and competition may not exist. Moreover, many environmental variables are temporal autocorrelated, but theory has largely focused on serially uncorrelated environments. To address this gap, a model of competing species in autocorrelated environments is analyzed. This analysis shows that positive autocorrelations in demographic rates that increase fitness (e.g., maximal fecundity or adult survival) produce the positive environment-competition covariance in condition (i). Hence, when these demographic rates contribute to buffered population growth, positive temporal autocorrelations generate a storage effect; otherwise, they destabilize competitive interactions. For negatively autocorrelated environments, this theory highlights an alternative stabilizing mechanism that requires three conditions: (i') there is a negative environment-competition covariance, (ii) there are species-specific environmental responses, and (iii') species are less sensitive to competition in more favorable years. When the conditions for either of these stabilizing mechanisms are violated, temporal autocorrelations can generate stochastic priority effects or hasten competitive exclusion. Collectively, these results highlight that temporal autocorrelations in environmental conditions can play a fundamental role in determining ecological outcomes of competing species.
摘要
环境波动可以通过存储效应介导竞争物种共存。这种依赖于波动的共存机制需要三个条件：（i）物种对环境条件的响应与竞争强度之间存在正协方差，（ii）存在物种特异性的环境响应，以及（iii）在环境不利的年份，物种对竞争的敏感性降低。在连续不相关的环境中，条件（i）仅在有利的环境条件立即且直接增加竞争强度时才会发生。对于许多人口参数，有利年份与竞争之间可能不存在这种直接联系。此外，许多环境变量是时间自相关的，但理论主要集中在连续不相关的环境上。为了解决这一差距，分析了自相关环境中竞争物种的模型。该分析表明，增加适合度的人口率的正自相关（例如，最大繁殖力或成年存活率）在条件（i）中产生正的环境-竞争协方差。因此，当这些人口率有助于缓冲种群增长时，正的时间自相关会产生存储效应；否则，它们会破坏竞争相互作用。对于负自相关环境，该理论强调了一种替代的稳定机制，该机制需要三个条件：（i'）存在负的环境-竞争协方差，（ii）存在物种特异性的环境响应，以及（iii'）在更有利的年份，物种对竞争的敏感性降低。当这些稳定机制的条件之一被违反时，时间自相关会产生随机优先效应或加速竞争排除。总的来说，这些结果表明，环境条件的时间自相关可以在决定竞争物种的生态结果方面发挥根本作用。
