The temporal storage effect—that species coexist by partitioning abiotic niches that vary in time—is thought to be an important explanation for how species coexist. However, empirical studies that measure multiple mechanisms often find the storage effect is weak. We believe this mismatch is because of a shortcoming of theoretical models used to study the storage effect: that while the storage effect is described as having just three requirements (partitioning of temporal variation, buffered population growth, and a covariance between environment and density-dependence), models used to study the storage effect make four assumptions, which are mathematically subtle but biologically important. In this paper, we examine those assumptions. First, models assume that environmental variation leads to a rapid impact on density-dependence. We find that delays in density-dependence (including delays caused by competition between cohorts) weaken the storage effect. Second, models assume that intraspecific competition is almost identical to interspecific competition. We find that unless resource or predator partitioning are virtually absent, then variation-independent mechanisms will overshadow the benefits of the storage effect. Third, models assume even though there is vast variation in the environment, species are equally adapted on average (i.e., zero fitness-differences). We show that fitness differences are particularly problematic in the storage effect because specializing on temporally rare niches is far less effective than specializing on other types of rare niches. Finally, models assume that stochastic extinctions can be ignored, and invader growth can determine coexistence. We show that storage effects tend to reduce mean persistence times, even if invader growth rates are positive. These results suggest that the assumptions needed for the storage effect are strict: if the first or second assumption is relaxed, it will greatly weaken the stabilizing mechanism; if the third or fourth assumption is relaxed, it will create a diversity-destroying effect that may undermine coexistence. We examine three real-world communities—annual plants, tropical forests, and iguanid lizards—and find that empirical studies suggest that all three communities violate multiple assumptions. This suggests that the temporal storage effect is probably not an important explanation for species diversity in most systems.

中文翻译：

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重新审视储存效应：为什么非生物因素的时间变化似乎不太可能导致共存

时间储存效应——物种通过划分随时间变化的非生物生态位而共存——被认为是物种如何共存的重要解释。然而，衡量多种机制的实证研究往往发现存储效应较弱。我们认为这种不匹配是因为用于研究存储效应的理论模型存在缺陷：虽然存储效应被描述为只有三个要求（时间变化的划分、缓冲的人口增长以及环境与密度依赖性之间的协方差） ），用于研究存储效应的模型做出了四个假设，这些假设在数学上很微妙，但在生物学上很重要。在本文中，我们研究了这些假设。首先，模型假设环境变化会对密度依赖性产生快速影响。我们发现密度依赖性的延迟（包括群体之间的竞争引起的延迟）削弱了存储效应。其次，模型假设种内竞争与种间竞争几乎相同。我们发现，除非资源或捕食者分区实际上不存在，否则变化无关的机制将掩盖存储效应的好处。第三，模型假设即使环境存在巨大差异，物种的平均适应能力也相同（即适应度差异为零）。我们表明，适应度差异在存储效应中尤其成问题，因为专门针对暂时稀有的生态位远不如专门针对其他类型的稀有生态位有效。最后，模型假设随机灭绝可以忽略不计，入侵者的增长可以决定共存。我们表明，即使入侵者增长率为正，存储效应也往往会减少平均持久时间。这些结果表明，存储效应所需的假设是严格的：如果放松第一个或第二个假设，将大大削弱稳定机制；如果放松第三个或第四个假设，就会产生破坏多样性的效应，从而可能破坏共存。我们研究了三个现实世界的群落——一年生植物、热带森林和鬣蜥——并发现实证研究表明这三个群落都违反了多种假设。这表明时间存储效应可能不是大多数系统中物种多样性的重要解释。