Intraguild predation in a structured habitat: distinguishing multiple-predator effects from competitor effects.
Intraguild predation in a structured habitat: distinguishing multiple-predator effects from competitor effects.
复制标题
结构化栖息地中的行会内捕食：区分多重捕食者效应和竞争者效应。
作者：
R. Schmitt;S. Holbrook;A. Brooks;Jennifer Lape
预测群落动态的能力，除其他外，需要了解相互作用物种网络中的间接影响和非线性，以及栖息地结构如何调节相互作用。我们对法属波利尼西亚莫雷亚珊瑚礁系统的这些方面进行了探索，涉及公会内捕食，其中共享的小自私猎物(幼年黄尾鱼Dascyllus Dascyllus Huang icaudus)和两种公会内(IG)猎物(埋伏捕食者弧眼鹰鱼、弧眼鹰鱼和红点珊瑚蟹Trapezia rufopunctata)共同栖息在分枝的多孔虫珊瑚中，以保护它们免受移动的IG捕食者的攻击。野外实验表明，两种IG猎物对幼鱼的生存都有很强的不利影响，但最主要的潜在过程是对无敌空间的竞争，而不是直接捕食。在这种情况下，鹰鱼和螃蟹的联合作用并没有增加或降低淡水鱼的风险。同样，IG捕食者和IG猎物对共享猎物的联合影响也与它们的独立影响预期的影响无法区分。栖息地结构削弱了IG-猎物-IG-捕食者之间的相互作用；IG猎物与小鱼的空间竞争比与IG捕食者的资源竞争要强得多。因此，不存在一个营养级联，使淡水鱼受益于IG捕食者对鹰鱼或珊瑚蟹的不利影响。这些结果突出了栖息地结构可以调节物种相互作用的方式，并强调了理解潜在机制的必要性。
The ability to forecast community dynamics requires, among other things, an understanding of indirect effects and nonlinearities in webs of interacting species, together with knowledge of how habitat structure mediates interactions. We explored these aspects for a coral reef system in Moorea, French Polynesia, involving intraguild predation where the shared damselfish prey (juvenile yellowtail dascyllus Dascyllusflavicaudus) and two species of intraguild (IG) prey (the ambush predators arc-eye hawkfish Paracirrhites arcatus and red-spotted coral crab Trapezia rufopunctata) shelter together in branching Pocilloporid corals for protection from mobile IG predators. Field experiments revealed that both IG prey had strong adverse effects on survivorship of juvenile damselfish, but that the dominant underlying process was competition for enemy-free space and not direct consumption. In this case, the combined effect of hawkfish and crabs did not result in either risk enhancement or risk reduction for the damselfish. Similarly, the combined influence of IG predators and IG prey on the shared prey also was indistinguishable from that expected from their independent effects. Habitat structure weakened the IG-prey-IG-predator interaction; IG prey were much stronger space competitors with damselfish than resource competitors with IG predators. As a consequence, there was not a trophic cascade where damselfish benefited by the adverse effect of IG predators on hawkfish or coral crabs. These results highlight the manner by which habitat structure can mediate species interactions and emphasize the need to understand the underlying mechanisms.