Department of Ecology and Environmental Science, Umeå University, SE-90187, Umeå, Sweden.
J Anim Ecol. 2013 Jan;82(1):55-63. doi: 10.1111/j.1365-2656.2012.02032.x. Epub 2012 Sep 24.
Size-dependent interactions and habitat complexity have been identified as important factors affecting the persistence of intraguild predation (IGP) systems. Habitat complexity has been suggested to promote intraguild (IG) prey and intraguild predator coexistence through weakening trophic interactions particularly the predation link. Here, we experimentally investigate the effects of habitat complexity on coexistence and invasion success of differently sized IG-predators in a size-structured IGP system consisting of the IG-predator Poecilia reticulata and a resident Heterandria formosa IG-prey population. The experiments included medium-long and long-term invasion experiments, predator-prey experiments and competition experiments to elucidate the mechanisms underlying the effect of prey refuges. Habitat complexity did not promote the coexistence of IG-predator and IG-prey, although the predation link was substantially weakened. However, the presence of habitat structure affected the invasion success of large IG-predators negatively and the invasion success of small IG-predators positively. The effect of refuges on size-dependent invasion success could be related to a major decrease in the IG-predator's capture rate and a shift in the size distribution of IG-predator juveniles. In summary, habitat complexity had two main effects: (i) the predation link was diminished, resulting in a more competition driven system and (ii) the overall competitive abilities of the two species were equalized, but coexistence was not promoted. Our results suggest that in a size-structured IGP system, individual level mechanisms may gain in importance over species level mechanisms in the presence of habitat complexity.
尺寸依赖性相互作用和栖息地复杂性已被确定为影响种内捕食（IGP）系统持久性的重要因素。栖息地复杂性被认为通过削弱特别是捕食关系的营养相互作用来促进种内（IG）猎物和种内捕食者共存。在这里，我们通过一个由种内捕食者 Poecilia reticulata 和驻留 Heterandria formosa IG 猎物种群组成的大小结构 IGP 系统的实验，研究了栖息地复杂性对不同大小 IG 捕食者共存和入侵成功的影响。实验包括中长和长期入侵实验、捕食者-猎物实验和竞争实验，以阐明猎物避难所效应的机制。尽管捕食关系大大减弱，但栖息地复杂性并没有促进 IG 捕食者和 IG 猎物的共存。然而，栖息地结构的存在对大 IG 捕食者的入侵成功产生负面影响，对小 IG 捕食者的入侵成功产生积极影响。避难所对尺寸依赖性入侵成功的影响可能与 IG 捕食者的捕获率大幅下降和 IG 捕食者幼体的大小分布发生变化有关。总之，栖息地复杂性有两个主要影响：（i）捕食关系减弱，导致更具竞争驱动的系统；（ii）两种物种的整体竞争能力均等化，但不促进共存。我们的研究结果表明，在大小结构的 IGP 系统中，在栖息地复杂性存在的情况下，个体水平的机制可能比物种水平的机制更为重要。
