Contrasting patterns of individual specialization and trophic coupling in two marine apex predators

摘要: 1. Apex predators are often assumed to be dietary generalists and, by feeding on prey from multiple basal nutrient sources, serve couple discrete food webs. But there is increasing evidence that individual level specialization may common in many species, and this has not been investigated for marine apex predators. 2. Because of their position at or near the top webs, possibility they can affect populations induce trophic cascades, it important understand patterns shark populations. 3. Stable isotope values body tissues with different turnover rates were used quantify two species 'generalist' sharks (bull sharks, Carcharhinus leucas, tiger Galeocerdo cuvier). 4. Despite wide population-level isotopic niche breadths both varied across rates. The population breadth was explained mostly variation within individuals suggesting true generalists. In contrast, bull stable through time among specialist individuals. 5. Relative resource abundance spatial food-predation risk tradeoffs explain differences between species. 6. results functional roles coupling compartmentalizing distinct 7. Individual an feature dynamics highly mobile should explicitly considered studies webs ecological role