Re-evaluating the distribution of cooperative breeding in birds: is it tightly linked with altriciality?

The evolution of cooperative breeding (CB) in birds has aroused intensive interest for decades, largely due to the paradox that some adults forgo independent breeding to help others. While much effort has been directed at understanding the adaptive significance of CB behavior, much less effort has been spent on understanding its origin. Ligon and Burt argued that the evolution of altriciality played a key role in the origin of CB since CB occurs more frequently in altricial lineages than expected if developmental mode and CB evolved independently and that both traits arose early in the avian tree of life. We mapped presence or absence of CB, and precocial or altricial development on a recent phylogeny of all birds to re-evaluate their conclusions. Our results suggest altriciality may be more recently derived than previously thought, and that CB species clustered in a derived land bird clade (especially within Passeriformes) where we reconstructed many gains and losses. We did find a lin...

数十年来，鸟类合作繁殖（cooperative breeding, CB）的演化一直引发学界广泛关注，这在很大程度上源于一个矛盾现象：部分成年个体放弃独立繁殖，转而协助其他个体繁衍后代。尽管学界已投入大量精力阐释合作繁殖行为的适应性意义，但针对其演化起源的研究却相对匮乏。利根（Ligon）与伯特（Burt）提出，晚成性（altriciality）的演化在合作繁殖的起源中发挥了关键作用——因为若发育模式与合作繁殖独立演化，那么合作繁殖在晚成雏类群中的出现频率应低于实际观测值；且二者均在鸟类生命之树的早期阶段就已出现。我们基于最新的全球鸟类系统发育树，对合作繁殖的有无以及早成性（precociality）、晚成性发育模式进行了性状映射标注，以此重新评估二人的结论。我们的研究结果显示，晚成性的演化起源可能比此前认为的更晚；且合作繁殖物种集中分布于一个衍生的陆禽支系（尤其集中在雀形目（Passeriformes）内），我们在该支系中重建出多次合作繁殖的起源与丢失事件。我们确实发现了一个演化支系（原文后续内容未完整呈现）。