Data from: Rates of karyotypic evolution in Estrildid finches differ between island and continental clades

Reasons why chromosomal rearrangements spread to fixation and frequently distinguish related taxa remain poorly understood. We used cytological descriptions of karyotype to identify large pericentric inversions between species of Estrildid finches (family Estrildidae) and a time-dated phylogeny to assess the genomic, geographic, and phylogenetic context of karyotype evolution in this group. Inversions between finch species fixed at an average rate of one every 2.26 My. Inversions were twice as likely to fix on the sex chromosomes compared to the autosomes. A high repeat density on the sex chromosomes may increase mutation rates, but other explanations via mutagenic input are not supported, as the number of inversions on a chromosome does not correlate with its length or map size. Inversions have fixed 3.3× faster in three continental clades than in two island chain clades, and fixation rate correlates with both range size and the number of sympatric species pairs. These results point to adaptation as the dominant mechanism driving fixation and suggest a role for gene flow in karyotype divergence. A review shows that the rapid karyotype evolution observed in the Estrildid finches appears to be more general across birds, and by implication other understudied taxa.染色体重排得以固定并常成为近缘类群分化标志的原因，目前仍未得到充分阐释。我们通过核型（karyotype）的细胞学描述，鉴定出梅花雀（Estrildid finches，隶属于梅花雀科Estrildidae）各物种间存在大片段臂间倒位（pericentric inversion），并借助时间校准的系统发育树（time-dated phylogeny），解析了该类群核型演化的基因组学、地理学与系统发育学背景。 雀类物种间的倒位固定速率平均为每2.26百万年1次。性染色体上的倒位固定概率是常染色体（autosome）的两倍。性染色体较高的重复序列密度（repeat density）或许会提升突变率，但其他基于诱变输入的解释并不成立——染色体上的倒位数量与其长度或遗传图谱大小并无相关性。 三个大陆演化支的倒位固定速率是两个岛屿链演化支的3.3倍，且固定速率与物种分布范围大小以及同域物种对（sympatric species pair）的数量均呈显著相关。上述结果表明，适应性演化是驱动倒位固定的主导机制，同时暗示基因流（gene flow）在核型分化中发挥了重要作用。 一项综述显示，梅花雀类所展现出的快速核型演化现象，在鸟类中似乎更为普遍，由此可推论该规律也适用于其他尚未被充分研究的类群。