School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
Oecologia. 2010 May;163(1):111-8. doi: 10.1007/s00442-009-1554-z. Epub 2010 Jan 6.
Both habitat complexity and priority effects can influence the strength of competitive interactions; however, the independent and synergistic effects of these processes are not well understood. In Moorea, French Polynesia, we conducted a factorial field experiment to quantify the independent and combined effects of priority effects and habitat complexity on the strength of intraspecific competitive interactions among recently settled individuals of a coral reef fish (Thalassoma quinquevittatum: Labridae). Simultaneous arrival of focal individuals with competitors resulted in a 2.89-fold increase in survival relative to reefs where focal individuals arrived 5 days later than competitors (i.e., a priority effect). Increasing habitat complexity resulted in a 1.55-fold increase in survivorship when focal individuals arrived simultaneously with or before competitors. However, increasing habitat complexity did not affect the survivorship of focal individuals arriving 5 days later than competitors. Behavior observations showed that survivorship was negatively correlated with aggression. Aggression by prior residents towards focal individuals was significantly greater when focal individuals arrived 5 days later than competitors than when they arrived simultaneously. Increasing habitat complexity did not reduce aggression. Our results suggest that, when competitors arrive simultaneously, competitive interactions are weak and subordinates are not displaced from complex habitat; increasing habitat complexity increases survival by disrupting predation. Conversely, when competitors arrive at different times, aggression intensifies and increasing habitat complexity does not disrupt predation because competitive subordinates are excluded from habitat resources. This study demonstrates that the strength of competition can be context-dependent and may vary with the timing of competitive interactions and habitat complexity.
生境复杂性和优先效应都可以影响竞争相互作用的强度；然而，这些过程的独立和协同效应还没有得到很好的理解。在法属波利尼西亚的莫雷阿岛，我们进行了一个析因现场实验，以量化优先效应和生境复杂性对最近定居的珊瑚礁鱼类（Thalassoma quinquevittatum：Labridae）种内竞争相互作用强度的独立和综合影响。与焦点个体比竞争者晚 5 天到达的珊瑚礁相比，焦点个体与竞争者同时到达会导致生存增加 2.89 倍（即优先效应）。当焦点个体与竞争者同时或更早到达时，增加生境复杂性会导致存活率增加 1.55 倍。然而，增加生境复杂性不会影响焦点个体比竞争者晚 5 天到达时的存活率。行为观察表明，存活率与攻击性呈负相关。当焦点个体比竞争者晚 5 天到达时，先到的居民对焦点个体的攻击性明显大于它们同时到达时。增加生境复杂性并不能减少攻击性。我们的结果表明，当竞争者同时到达时，竞争相互作用较弱，下属不会从复杂的生境中被排挤出去；增加生境复杂性可以通过破坏捕食来提高存活率。相反，当竞争者在不同时间到达时，攻击性会加剧，而增加生境复杂性并不能破坏捕食，因为竞争的下属被排除在生境资源之外。这项研究表明，竞争的强度可能是依赖于环境的，并且可能随竞争相互作用和生境复杂性的时间变化而变化。
