Abstract：
Extant birds stand out among vertebrates in the diversity of parental care types they present, spanning absence of care to uniparental care by either sex, biparental or even cooperative care. Despite years of research, key questions remain regarding parental care evolution in birds. Firstly, the parental care type in the most recent ancestor of extant birds is a matter of controversy, with proposed ancestral states including no care, uniparental male or female care, and biparental care. Another unsolved question is the direction, order, and frequency of transitions between parental care types. We address these key questions using a database of 5,438 bird species (~50% of extant diversity) and modern phylogenetic comparative methods controlling simultaneously for model and phylogenetic uncertainty as well as potential confounding effects of state-dependent diversification. Our results indicate that the most likely ancestral state for extant birds is male-only care, with a posterior probability of 0.8. Transition rates across parental care types were generally low and heterogenous; loss of parental care virtually never occurs and transitions away from female only or cooperative care most often lead to biparental care. Given the low transition rates, future research should analyze the factors favoring the maintenance of care types.
摘要：
现存的鸟类在脊椎动物中脱颖而出，它们表现出父母照料类型的多样性，从缺乏照顾到单亲照顾，双亲甚至合作照顾。尽管经过多年的研究,关于鸟类父母照顾的演变，关键问题仍然存在。首先,现存鸟类的最新祖先中的父母照顾类型是一个有争议的问题，提议的祖先州包括不照顾，单亲男性或女性护理，和双亲照顾。另一个未解决的问题是方向，订单,以及父母照料类型之间转换的频率。我们使用5,438种鸟类（约占现有多样性的50％）的数据库和现代系统发育比较方法同时控制模型和系统发育不确定性以及状态依赖性多样化的潜在混杂效应来解决这些关键问题。我们的结果表明，现存鸟类最可能的祖先状态是仅男性护理，后验概率为0.8。父母照料类型的过渡率通常较低且异质；父母照料的丧失几乎从未发生过，而从女性照料或合作照料的过渡通常会导致双亲照料。鉴于过渡期较低，未来的研究应该分析有利于维护护理类型的因素。
