Data from: Predation risk, resource quality, and reef structural complexity shape territoriality in a coral reef herbivore

For many species securing territories is important for feeding and reproduction. Factors such as competition, habitat availability, and male characteristics can influence an individual’s ability to establish and maintain a territory. The risk of predation can have an important influence on feeding and reproduction; however, few have studied its effect on territoriality. We investigated territoriality in a haremic, polygynous species of coral reef herbivore, Sparisoma aurofrenatum (redband parrotfish), across eight reefs in the Florida Keys National Marine Sanctuary that were either protected or unprotected from fishing of piscivorous fishes. We examined how territory size and quality varied with reef protection status, competition, predation risk, and male size. We then determined how territory size and quality influenced harem size and female size to understand the effect of territoriality on reproductive potential. We found that protected reefs trended towards having more large predatory fishes and that territories there were smaller but had greater algal nutritional quality relative to unprotected reefs. Our data suggest that even though males in protected sites have smaller territories, which support fewer females, they may improve their reproductive potential by choosing nutritionally rich areas, which support larger females. Thus, reef protection appears to shape the trade-off that herbivorous fishes make between territory size and quality. Furthermore, we provide evidence that males in unprotected sites, which are generally less complex than protected sites, choose territories with higher structural complexity, suggesting the importance of this type of habitat for feeding and reproduction in S. aurofrenatum. Our work argues that the loss of corals and the resulting decline in structural complexity, as well as management efforts to protect reefs, could alter the territory dynamics and reproductive potential of important herbivorous fish species.对诸多物种而言，划定并守护领地对于觅食与繁衍至关重要。种内竞争、栖息地可获取性以及雄性个体特征等因素，均可影响个体建立并维持领地的能力。捕食风险（predation risk）同样会对觅食与繁衍产生重要影响，但目前针对其对领地行为（territoriality）的影响的研究仍较为有限。本研究以珊瑚礁植食性动物（herbivore）——红带鹦嘴鱼（Sparisoma aurofrenatum，Redband parrotfish）这一实行后宫制（haremic）、一雄多雌制（polygynous）的物种为研究对象，在佛罗里达群岛国家海洋保护区（Florida Keys National Marine Sanctuary）的8处珊瑚礁开展调查，这些礁区分别实施或未实施掠食性鱼类（piscivorous fishes）捕捞保护措施。本研究探讨了领地面积与质量如何随礁区保护状态、种内竞争强度、捕食风险以及雄性个体体型发生变化；随后分析了领地面积与质量对后宫群体规模及雌性个体体型的影响，以揭示领地行为对繁殖潜力（reproductive potential）的作用机制。研究发现，相较于未保护礁区，受保护礁区的大型掠食性鱼类丰度更高，其内雄鱼的领地面积更小，但藻类的营养品质更佳。本研究数据表明，尽管受保护区域内的雄鱼领地更小，所能容纳的雌性个体数量更少，但它们可通过选择营养丰富的领地——这类领地可孕育体型更大的雌性——来提升自身繁殖潜力。由此可见，礁区保护政策似乎塑造了植食性鱼类在领地面积与质量之间的权衡策略。此外，本研究证实，未保护礁区的生境结构复杂度（structural complexity）通常低于受保护礁区，而该区域的雄鱼会选择结构复杂度更高的领地，这表明此类生境对红带鹦嘴鱼的觅食与繁衍具有重要意义。本研究认为，珊瑚礁退化导致的生境结构复杂度下降，以及礁区保护管理措施，均可能改变重要植食性鱼类的领地动态与繁殖潜力。