ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4810, Australia.
Biology Department, Stanford University, Stanford, CA, 94305, USA.
Sci Rep. 2018 Apr 19;8(1):6295. doi: 10.1038/s41598-018-24412-0.
Pair bonding is generally linked to monogamous mating systems, where the reproductive benefits of extended mate guarding and/or of bi-parental care are considered key adaptive functions. However, in some species, including coral reef butterflyfishes (f. Chaetodonitidae), pair bonding occurs in sexually immature and homosexual partners, and in the absence of parental care, suggesting there must be non-reproductive adaptive benefits of pair bonding. Here, we examined whether pair bonding butterflyfishes cooperate in defense of food, conferring direct benefits to one or both partners. We found that pairs of Chaetodon lunulatus and C. baronessa use contrasting cooperative strategies. In C. lunulatus, both partners mutually defend their territory, while in C. baronessa, males prioritize territory defence; conferring improvements in feeding and energy reserves in both sexes relative to solitary counterparts. We further demonstrate that partner fidelity contributes to this function by showing that re-pairing invokes intra-pair conflict and inhibits cooperatively-derived feeding benefits, and that partner endurance is required for these costs to abate. Overall, our results suggest that in butterflyfishes, pair bonding enhances cooperative defense of prey resources, ultimately benefiting both partners by improving food resource acquisition and energy reserves.
配对结合通常与一夫一妻制的交配系统相关联，在这种系统中，延长配偶保护和/或双亲照顾的生殖益处被认为是关键的适应功能。然而，在一些物种中，包括珊瑚礁蝴蝶鱼（Chaetodonitidae 科），配对结合发生在性未成熟和同性恋伴侣中，并且没有亲代照顾，这表明配对结合一定有非生殖适应性益处。在这里，我们研究了配对蝴蝶鱼是否在防御食物方面进行合作，从而为一个或两个伴侣带来直接利益。我们发现，配对的 Lunulatus 蝴蝶鱼和 Baronessa 蝴蝶鱼使用了截然不同的合作策略。在 Lunulatus 蝴蝶鱼中，双方共同保护其领地，而在 Baronessa 蝴蝶鱼中，雄性则优先保护领地；与独居的同类相比，这两种性别都能提高摄食和能量储备。我们进一步证明，伴侣忠诚度有助于发挥这一功能，因为它表明重新配对会引起伴侣之间的冲突，并抑制合作带来的摄食益处，并且需要伴侣的耐力才能减轻这些成本。总的来说，我们的结果表明，在蝴蝶鱼中，配对结合增强了对猎物资源的合作防御，最终通过提高食物资源获取和能量储备使双方受益。
