Dauphin Island Sea Lab, Dauphin Island, Alabama, USA.
Department of Marine Science, University of South Alabama, Mobile, Alabama, USA.
Ecology. 2023 Jun;104(6):e4050. doi: 10.1002/ecy.4050. Epub 2023 May 2.
The capacity of an apex predator to produce nonconsumptive effects (NCEs) in multiple prey trophic levels can create considerable complexity in nonconsumptive cascading interactions, but these effects are poorly studied. We examined such effects in a model food web where the apex predator (blue crabs) releases chemical cues in urine that affect both the intermediate consumer (mud crabs seek shelter) and the basal prey (oysters are induced to grow stronger shells). Shelter availability and predator presence were manipulated in a laboratory experiment to identify patterns in species interactions. Then, experimentally induced and uninduced oysters were planted across high-quality and low-quality habitats with varying levels of shelter availability and habitat heterogeneity to determine the consistency of these patterns in the field. Oyster shell thickening in response to blue crab chemical cues generally protected oysters from mud crab predation in both the laboratory and in field environments that differed in predation intensity, structural complexity, habitat heterogeneity, and predator composition. However, NCEs on the intermediate predator (greater use of refugia) opposed the NCEs on oyster prey in the interior of oyster reefs while still providing survival advantages to basal prey on reef edges and bare substrates. Thus, the combined effects of changing movement patterns of intermediate predators and morphological defenses of basal prey create complex, but predictable, patterns of NCEs across landscapes and ecotones that vary in structural complexity. Generalist predators that feed on multiple trophic levels are ubiquitous, and their potential effects on NCEs propagating simultaneously to different trophic levels must be quantified to understand the role of NCEs in food webs.
顶级捕食者在多个猎物营养层产生非消耗性影响（NCEs）的能力会在非消耗性级联相互作用中产生相当大的复杂性，但这些影响的研究还很薄弱。我们在一个模型食物网中研究了这些影响，其中顶级捕食者（蓝蟹）在尿液中释放化学信号，影响中间消费者（泥蟹寻找庇护所）和基础猎物（牡蛎被诱导生长更强壮的壳）。在实验室实验中操纵庇护所的可用性和捕食者的存在，以确定物种相互作用的模式。然后，将实验诱导和未诱导的牡蛎种植在具有不同庇护所可用性和栖息地异质性水平的高质量和低质量栖息地中，以确定这些模式在野外的一致性。牡蛎对蓝蟹化学信号的反应导致牡蛎壳变厚，通常可以保护牡蛎免受泥蟹的捕食，无论是在实验室还是在捕食强度、结构复杂性、栖息地异质性和捕食者组成不同的野外环境中。然而，中间捕食者（更多地利用避难所）的 NCEs 与牡蛎猎物的 NCEs 相矛盾，而在牡蛎礁内部仍然为礁边缘和裸露基质上的基础猎物提供生存优势。因此，中间捕食者运动模式的变化和基础猎物形态防御的综合作用在结构复杂性不同的景观和生态交错带中产生了复杂但可预测的 NCEs 模式。以多个营养层为食的广食性捕食者无处不在，它们对同时向不同营养层传播的 NCEs 的潜在影响必须加以量化，以了解 NCEs 在食物网中的作用。
