1. Globally endangered ecosystems, such as ephemeral wetlands, are often critical habitat for multiple interacting imperilled species. To conserve this biodiversity, managers must consider both species-specific resource requirements and mechanisms for endangered species coexistence under variable habitat conditions.
2. We examined communities native to California playa pools, ephemeral wetlands that have declined by >90% from their historic extent. Specifically, we describe the diet of a federally Threatened amphibian (Ambystoma californiense), and characterise interactions between this amphibian and two federally Endangered macrocrustaceans (Branchinecta conservatio and Lepidurus packardi) across three rain years to understand how these imperilled species coexist. We examined the dietary preferences of A. californiense larvae, metamorphs, juveniles, and breeding adults, and determined how prey electivity by larval A. californiense differs between natural playa pools and human-modified stock ponds.
3. Within playa pools, both breeding adult and larval A. californiense preyed extensively on L. packardi, whereas fully terrestrial juveniles had relatively empty stomachs. We provide evidence for size-moderated optimal foraging by larval A. californiense, and show that larval prey differed dramatically between playa pools and stock ponds. Additionally, an ontogenetic progression from smaller to larger prey gave the relatively large, endangered macrocrustaceans an early-season temporal refuge, during which they reached maturity in all three rain years.
4. Consistent with complex life cycle theory, our results suggest that ephemeral wetland habitat offers abundant food resources for A. californiense relative to terrestrial habitat. Our findings also suggest that diet flexibility facilitates the persistence of this imperilled amphibian in human-modified stock ponds. Temporal offsets in prey maturation rates and ontogenetic shifts in predator diets are likely to facilitate coexistence among the focal endangered species.
5. We highlight the importance of accounting for spatial and temporal variation in interspecific interactions when predicting the effects of environmental change on biodiversity, particularly in highly threatened ecosystems.

中文翻译：

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加利福尼亚春季水池中濒临灭绝的捕食者-猎物社区的共存

1. 全球濒临灭绝的生态系统，例如短暂的湿地，通常是多种相互作用的濒危物种的重要栖息地。为了保护这种生物多样性，管理人员必须考虑特定物种的资源需求和不同栖息地条件下濒危物种共存的机制。
2. 我们研究了加利福尼亚海滩泳池的原生社区，这些临时湿地比历史范围下降了 90% 以上。具体来说，我们描述了联邦受威胁的两栖动物 ( Ambystoma californiense )的饮食，并描述了这种两栖动物与两种联邦濒危大型甲壳类动物 ( Branchinecta conservatio和Lepidurus packardi ) 在三个雨年之间的相互作用，以了解这些濒危物种如何共存。我们检查了A. californiense幼虫、变体、幼体和繁殖成虫的饮食偏好，并确定了A. californiense幼虫的猎物选择性在天然海滩池和人工改造的池塘之间有何不同。
3. 在滩池，养殖成虫和幼虫都A. californiense广泛捕食L. packardi，而全地面青少年具有相对饿着肚子。我们提供了幼虫A. californiense进行大小调节的最佳觅食的证据，并表明幼虫猎物在海滩池和种群池塘之间存在显着差异。此外，从较小到较大的猎物的个体发育过程为相对较大的濒危大型甲壳类动物提供了早期的时间避难所，在此期间它们在所有三个雨年都达到了成熟。
4. 与复杂生命周期理论一致，我们的结果表明，相对于陆地栖息地，短暂的湿地栖息地为A. californiense提供了丰富的食物资源。我们的研究结果还表明，饮食的灵活性有助于这种濒危两栖动物在人类改造的池塘中的持久性。猎物成熟率的时间偏移和捕食者饮食的个体发生变化可能会促进重点濒危物种之间的共存。
5. 我们强调在预测环境变化对生物多样性的影响时，特别是在高度受威胁的生态系统中，考虑种间相互作用的空间和时间变化的重要性。