Assessing the applicability of theory to major adaptive radiations in deep time represents an extremely difficult problem in evolutionary biology. Neoaves, which includes 95% of living birds, is believed to have undergone a period of rapid diversification roughly coincident with the Cretaceous–Paleogene (K-Pg) boundary. We investigate whether basal neoavian lineages experienced an ecological release in response to ecological opportunity, as evidenced by density compensation. We estimated effective population sizes (Ne) of basal neoavian lineages by combining coalescent branch lengths (CBLs) and the numbers of generations between successive divergences. We used a modified version of Accurate Species TRee Algorithm (ASTRAL) to estimate CBLs directly from insertion–deletion (indel) data, as well as from gene trees using DNA sequence and/or indel data. We found that some divergences near the K-Pg boundary involved unexpectedly high gene tree discordance relative to the estimated number of generations between speciation events. The simplest explanation for this result is an increase in Ne, despite the caveats discussed herein. It appears that at least some early neoavian lineages, similar to the ancestor of the clade comprising doves, mesites, and sandgrouse, experienced ecological release near the time of the K-Pg mass extinction.

中文翻译：

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深度人口统计学推断表明生态释放是新禽类自适应辐射的驱动力

评估理论在深度时间内对主要适应性辐射的适用性是进化生物学中一个极其困难的问题。Neoaves包括95％的活禽，据信经历了一个快速多样化的时期，大致与白垩纪-古近缘（K-Pg）边界重合。我们调查了基底新禽系是否响应生态机会而经历了生态释放，如密度补偿所证明的。我们估算了有效的人口规模（Ne通过合并合并分支长度（CBLs）和连续发散之间的世代数来确定新鸟类基础谱系。我们使用了Accurate Species TRee算法（ASTRAL）的改进版本，可以直接从插入缺失（indel）数据以及使用DNA序列和/或indel数据的基因树中估计CBL。我们发现，相对于物种形成事件之间的估计世代数，K-Pg边界附近的一些差异涉及出乎意料的高基因树不一致。最简单的解释是Ne的增加，尽管本文讨论了注意事项。似乎至少有一些早期的新鸟类谱系，类似于包含鸽子，中生点和沙鸡的进化枝的祖先，在K-Pg大规模灭绝时经历了生态释放。