Tidal regime dictates the cascading consumptive and nonconsumptive effects of multiple predators on a marsh plant
Tidal regime dictates the cascading consumptive and nonconsumptive effects of multiple predators on a marsh plant
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DOI：
10.1890/11-0596.1
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发表时间：
2012-02-01
期刊：
影响因子：
4.8
通讯作者：
Kimbro, David L.
中科院分区：
文献类型：
--
作者：
Kimbro, David L.
猎物对捕食者的感知可以决定猎物如何在行为上平衡避免被吃掉的需要和消耗资源的需要，并且这种感知和随之而来的行为可能会受到物理过程的强烈影响。然而，物理因素也会改变捕食者捕食猎物的密度和多样性。因此，仍然不确定可变的风险感知和反捕食者行为与捕食者对猎物的消耗的变化在多大程度上构成了猎物资源动态的基础，并在自然系统中引起了大规模的模式。在一个实验食物网中，沼泽的潮汐淹没控制了捕食者接近猎物的方式，螃蟹和海螺（捕食者）影响了蜗牛（猎物）的生存和反捕食行为，无论潮汐淹没是在白天还是混合半日发生。具体来说，任一捕食者的线索都会导致蜗牛爬上沼泽树叶；不受限制的螃蟹比不受限制的海螺更能降低蜗牛的存活率；尽管存在干扰，但在多个捕食者的情况下，蜗牛的存活率比任何单一捕食者的存活率最低。与这些潮汐一致的直接消耗和非消耗效应相反，间接捕食者效应因潮汐状态而异：在日潮中，在捕食者存在的情况下，蜗牛对沼泽树叶的吃草量增加，但在混合半日潮汐时间表中减少，压倒了直接捕食导致的蜗牛密度差异。此外，结果表明，在捕食者提示存在的情况下，蜗牛可能会增加觅食，以补偿压力引起的代谢需求。跨越 400 公里海岸线的潮汐淹没梯度（从日潮到混合半日潮）的天然沼泽的模式与实验结果一致：尽管捕食者、蜗牛、非生物应激源和沼泽生产力的密度空间变化很小，但在暴露于日潮的海岸线上，蜗牛对沼泽植物的吃草增加，植物生物量减少。由于现场和实验结果都可以通过潮汐引起的风险感知和蜗牛行为的变化来解释，而不是通过蜗牛密度的变化来解释，因此这项研究强调了复杂自然系统和大空间尺度中非消耗性捕食者效应的重要性。
Prey perception of predators can dictate how prey behaviorally balance the need to avoid being eaten with the need to consume resources, and this perception and consequent behavior can be strongly influenced by physical processes. Physical factors, however, can also alter the density and diversity of predators that pursue prey. Thus, it remains uncertain to what extent variable risk perception and antipredator behavior vs. variation in predator consumption of prey underlie prey-resource dynamics and give rise to large-scale patterns in natural systems. In an experimental food web where tidal inundation of marsh controls which predators access prey, crab and conch (predators) influenced the survivorship and antipredator behavior of snails (prey) irrespective of whether tidal inundation occurred on a diurnal or mixed semidiurnal schedule. Specifically, cues of either predator caused snails to ascend marsh leaves; snail survivorship was reduced more by unrestrained crabs than by unrestrained conchs; and snail survivorship was lowest with multiple predators than with any single predator despite interference. In contrast to these tidally consistent direct consumptive and nonconsumptive effects, indirect predator effects differed with tidal regime: snail grazing of marsh leaves in the presence of predators increased in the diurnal tide but decreased in the mixed semidiurnal tidal schedule, overwhelming the differences in snail density that resulted from direct predation. In addition, results suggest that snails may increase their foraging to compensate for stress-induced metabolic demand in the presence of predator cues. Patterns from natural marshes spanning a tidal inundation gradient (from diurnal to mixed semidiurnal tides) across 400 km of coastline were consistent with experimental results: despite minimal spatial variation in densities of predators, snails, abiotic stressors, and marsh productivity, snail grazing on marsh plants increased and plant biomass decreased on shorelines exposed to a diurnal tide. Because both the field and experimental results can be explained by tidal-induced variation in risk perception and snail behavior rather than by changes in snail density, this study reinforces the importance of nonconsumptive predator effects in complex natural systems and at large spatial scales.