Changes in chromosome numbers may strongly affect reproductive barriers, because individuals heterozygous for distinct karyotypes are typically expected to be at least partially sterile or to show reduced recombination. Therefore, several classic speciation models are based on chromosomal changes. One import mechanism generating variation in chromosome numbers is fusion and fission of existing chromosomes, which is particularly likely in species with holocentric chromosomes, i.e. chromosomes that lack a single centromere. Holocentric chromosomes evolved repeatedly across the tree of life, including in Lepidoptera. Although changes in chromosome numbers are hypothesized to be an important driver of the spectacular diversification of Lepidoptera, comparative studies across the order are lacking. We performed the first comprehensive literature survey of karyotypes for Lepidoptera species since the 1970s and tested if, and how, chromosomal variation might affect speciation. Even though a meta-analysis of karyological differences between closely related taxa did not reveal an effect on the degree of reproductive isolation, phylogenetic diversification rate analyses across the 16 best-covered genera indicated a strong, positive association of rates of chromosome number evolution and speciation. These findings suggest a macroevolutionary impact of varying chromosome numbers in Lepidoptera and likely apply to other taxonomic groups, especially to those with holocentric chromosomes.

This article is part of the theme issue ‘Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers’.

染色体数量的变化可能会强烈影响生殖障碍，因为对于不同核型的杂合个体通常预计至少部分不育或显示重组减少。因此，几种经典的物种形成模型都是基于染色体变化的。产生染色体数目变异的一种重要机制是现有染色体的融合和裂变，这在具有全着丝染色体的物种中尤其可能，即缺乏单个着丝粒的染色体。全中心染色体在生命之树中反复进化，包括在鳞翅目中。尽管染色体数量的变化被假设是鳞翅目惊人多样化的重要驱动因素，但缺乏对整个目的比较研究。自 1970 年代以来，我们对鳞翅目物种的核型进行了第一次全面的文献调查，并测试了染色体变异是否以及如何影响物种形成。尽管对密切相关的分类群之间的核学差异的荟萃分析没有揭示对生殖隔离程度的影响，但对 16 个覆盖最广的属的系统发育多样化率分析表明，染色体数目进化和物种形成率之间存在强烈的正相关关系. 这些发现表明鳞翅目中不同染色体数量的宏观进化影响可能适用于其他分类群，

这篇文章是主题问题“走向物种形成的完成：超越第一道障碍的生殖隔离的进化”的一部分。