Peyton Kimberly A, Valentino Lauren M, Maruska Karen P
Hawaii Institute of Marine Biology, University of Hawaii - Manoa, Kaneohe, Hawaii, United States of America.
Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America.
PLoS One. 2014 Oct 15;9(10):e109007. doi: 10.1371/journal.pone.0109007. eCollection 2014.
Herbivory is a fundamental process determining reef resilience, and while algal farming damselfishes can help shape benthic assemblages, an understanding of their contribution to areas outside of defended territories is relatively unexplored. Here, we demonstrate how the farming damselfish Stegastes marginatus plays a dual role in benthic structuring by 1) contributing to persistence of the invasive macroalga Acanthophora spicifera within a Hawaiian marine protected area, where the macroalga occurred exclusively inside Stegastes territories, and 2) behaving as an opportunistic browser of the exotic alga outside their territorial borders. Greater than 50% of the biomass of tethered A. spicifera was consumed within one-hour when placed outside Stegastes territories, compared to <5% lost from tethers within territories or herbivore exclusion cages. In situ remote video revealed that tethered A. spicifera located outside territories was grazed primarily by the surgeonfish Acanthurus nigrofuscus (∼68% of total bites) and, surprisingly, by S. marginatus (∼27% of total bites) that left their territories to feed on this resource on 107 occasions during 400 min of filming. Further, for over half of those occurrences where S. marginatus grazed on the tethered macroalga outside of territories, they fed alongside conspecifics and other species, displaying little of the aggressiveness that characterizes this damselfish. These results show that S. marginatus plays a wider role in determining benthic assemblages than previously recognized, acting both as cultivators of a canopy-forming invasive macroalga within their territories, and as opportunistic browsers in neighboring sites. Consequently, S. marginatus can affect benthic species composition across their territory borders. These results provide a rare example of interspecific facilitation of an exotic alga by an indigenous marine fish. Accounting for fish behaviors more broadly is important to further our understanding of ecological processes that shape reef ecosystems to improve management of MPAs that often support extensive farming damselfish populations.
食草作用是决定珊瑚礁恢复力的一个基本过程，虽然养殖藻类的雀鲷可以帮助塑造底栖生物群落，但对于它们在受保护领地之外区域的贡献，人们了解得还相对较少。在这里，我们展示了养殖雀鲷缘边锯尾雀鲷（Stegastes marginatus）如何在底栖生物结构形成中发挥双重作用：1）促成入侵大型藻类尖刺卡帕藻（Acanthophora spicifera）在夏威夷海洋保护区内的持续存在，该大型藻类仅出现在缘边锯尾雀鲷的领地内；2）在其领地边界之外，作为外来藻类的机会主义食草者。当放置在缘边锯尾雀鲷领地之外时，超过50%的附着尖刺卡帕藻生物量在一小时内被消耗，而在领地内或食草动物排除笼中的附着藻损失不到5%。原位远程视频显示，位于领地外的附着尖刺卡帕藻主要被刺尾鱼黑褐刺尾鱼（Acanthurus nigrofuscus）啃食（约占总啃咬次数的68%），令人惊讶的是，缘边锯尾雀鲷也会啃食（约占总啃咬次数的27%），在400分钟的拍摄过程中，它们离开领地107次去啃食这种资源。此外，在超过一半的缘边锯尾雀鲷在领地外啃食附着大型藻类的情况下，它们与同种和其他物种一起进食，几乎没有表现出这种雀鲷典型的攻击性。这些结果表明，缘边锯尾雀鲷在决定底栖生物群落方面所起的作用比之前认识到的更为广泛，它既是领地内形成冠层的入侵大型藻类的培育者，也是邻近区域的机会主义食草者。因此，缘边锯尾雀鲷可以影响其领地边界两侧的底栖物种组成。这些结果提供了一个本土海洋鱼类对外来藻类进行种间促进作用的罕见例子。更全面地考虑鱼类行为对于进一步理解塑造珊瑚礁生态系统的生态过程很重要，有助于改善对通常支持大量养殖雀鲷种群的海洋保护区的管理。
