Disturbance plays a key role in structuring community dynamics and is central to conservation and natural resource management. However, ecologists continue to debate the importance of disturbance for species coexistence and biodiversity. Such disagreements may arise in part because few studies have examined variation across multiple dimensions of disturbance (e.g., size, frequency) and how the effects of disturbance may depend on species attributes (e.g., competitiveness, dispersal ability). In light of this gap in understanding and accelerating changes to disturbance regimes worldwide, we used spatial population models to explore how disturbance size and frequency interact with species attributes to affect coexistence between seagrass (Zostera marina) and colonial burrowing shrimp (Neotrypaea californiensis) that compete for benthic space in estuaries throughout the west coast of North America. By simulating population dynamics under a range of ecologically-relevant disturbance regimes, we discovered that intermediate disturbance (approximately 9-23% of landscape area per year) to short-dispersing, competitively-dominant seagrass can foster long-term stable coexistence with broad-dispersing, competitively-inferior burrowing shrimp via the spatial storage effect. When holding the total extent of disturbance constant, the individual size and annual frequency of disturbance altered landscape spatial patterns and mediated the dominance and evenness of competitors. Many small disturbances favored short-dispersing seagrass by hastening recolonization, whereas fewer large disturbances benefitted rapidly-colonizing burrowing shrimp by creating temporary refugia from competition. As a result, large, infrequent disturbances generally improved the strength and stability of coexistence relative to small, frequent disturbances. Regardless of disturbance size or frequency, the dispersal ability of the superior competitor (seagrass), the competitive ability the inferior competitor (burrowing shrimp), and the reproduction and survival of both species strongly influenced population abundances and coexistence. Our results show that disturbance size and frequency can promote or constrain coexistence by altering the duration of time over which inferior competitors can escape competitive exclusion, particularly when colonization depends on the spatial pattern of disturbance due to dispersal traits. For coastal managers and conservation practitioners, our findings indicate that reducing particularly large disturbances may help conserve globally-imperiled seagrass meadows and control burrowing shrimp colonies that can threaten the viability of oyster aquaculture.

中文翻译：

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干扰大小和频率介导底栖空间竞争者的共存

干扰在构建社区动态方面起着关键作用，并且是保护和自然资源管理的核心。然而，生态学家继续争论干扰对物种共存和生物多样性的重要性。产生这种分歧的部分原因可能是因为很少有研究考察干扰的多个维度（例如，大小、频率）的变化以及干扰的影响如何取决于物种属性（例如，竞争力、扩散能力）。鉴于在理解和加速全球扰动机制变化方面的差距，我们使用空间种群模型来探索干扰大小和频率如何与物种属性相互作用，以影响海草 (Zostera marina) 和群居穴居虾 (Neotrypaea californiensis) 之间的共存，它们在整个北美西海岸的河口争夺底栖空间。通过模拟一系列与生态相关的干扰机制下的种群动态，我们发现中度干扰（每年大约占景观面积的 9-23%）对短时间分散、竞争优势的海草可以促进与广泛的长期稳定共存。通过空间存储效应分散、竞争劣势的穴居虾。当保持总扰动程度不变时，个体规模和年度干扰频率改变了景观空间格局并调节了竞争者的优势和均匀度。许多小干扰通过加速重新定植有利于短距离海草，而较少的大干扰通过在竞争中创造临时避难所使快速定植的穴居虾受益。因此，相对于小而频繁的干扰，大的、不频繁的干扰通常会提高共存的强度和稳定性。无论干扰大小或频率如何，优势竞争者（海草）的传播能力、劣势竞争者（穴居虾）的竞争能力以及两个物种的繁殖和生存都强烈影响种群丰度和共存。我们的结果表明，干扰的大小和频率可以通过改变劣势竞争者逃避竞争排斥的持续时间来促进或限制共存，特别是当殖民化取决于分散特征引起的干扰空间模式时。对于沿海管理者和保护从业者，我们的研究结果表明，减少特别大的干扰可能有助于保护全球濒临灭绝的海草草甸，并控制可能威胁牡蛎养殖可行性的穴居虾群。