Data from: Going to extremes: contrasting rates of diversification in a recent radiation of New World passerine birds

Recent analyses suggest that a few major shifts in diversification rate may be enough to explain most of the disparity in diversity among vertebrate lineages. At least one significant increase in diversification rate appears to have occurred within the birds; however, several nested lineages within birds have been identified as hyperdiverse by different studies. A clade containing the finches and relatives (within the avian order Passeriformes), including a large radiation endemic to the New World that comprises ~8% of all bird species, may be the true driver of this rate increase. Understanding the patterns and processes of diversification of this diverse lineage may go a long way toward explaining the apparently rapid diversification rates of both passerines and of birds as a whole. We present the first multi-locus phylogenetic analyses of this endemic New World radiation of finch relatives that includes sampling of all recognized genera, a relaxed molecular clock analysis of its divergence history, and an analysis of its broad-scale diversification patterns. These analyses recover five major lineages traditionally recognized as avian families, but identify an additional ten relatively ancient lineages worthy of recognition at the family level. Time-calibrated diversification analyses suggest that at least six of the fifteen family-level lineages are significantly species-poor given the entire group’s background diversification rate, whereas one—the tanagers of family Thraupidae—is significantly more diverse. These differences are consistent with the low speciation and extinction rates of island and ecologically-specialized lineages previously documented across passerines as a whole. Finally, lack of an age-diversity relationship within this clade suggests that, due to rapid initial speciation, it may have experienced density-dependent ecological limits on its overall diversity.

近期研究表明，仅需数次主要的多样化速率（diversification rate）转变，即可解释脊椎动物类群间绝大多数的多样性差异。鸟类支系中至少发生过一次显著的多样化速率提升；然而不同研究均已发现，鸟类内部的多个嵌套支系属于超高多样性类群。包含雀类及其近缘类群的支系（隶属于鸟类雀形目（Passeriformes）），其中涵盖了一个占全球鸟类物种约8%的新大陆特有辐射演化类群，可能正是此次多样化速率提升的真正驱动因素。阐明该物种丰富支系的多样化模式与形成过程，将极大助力我们理解雀形目鸟类乃至整个鸟类类群看似快速的多样化速率。
本研究首次针对该新大陆特有雀类近缘类群开展多基因座系统发育分析，采样覆盖了所有已确认的属；同时进行了松弛分子钟（relaxed molecular clock）分析以探究其分化历史，并解析了其大尺度多样化格局。此次分析恢复了5个传统上被认定为鸟类科级阶元的支系，同时额外鉴定出10个相对古老的支系，具备科级分类阶元的分类价值。
时间校准的多样化分析显示，在15个科级支系中，相较于该类群的背景多样化速率，至少有6个支系的物种丰度显著偏低；而裸鼻雀科（Thraupidae）的唐纳雀类则显著更为多样。上述差异与此前针对整个雀形目鸟类所记录的岛屿类群与生态特化类群较低的成种与灭绝速率相一致。最后，该支系内部未呈现年龄-多样性相关性，这表明由于初始快速成种作用，其整体多样性可能已达到了密度依赖的生态极限。