The study investigates the role of chromosomal fusion and fission in the macroevolutionary process of speciation in the genus *Erebia*, a group of butterflies with high karyotype diversity. Chromosomal rearrangements, particularly fusions and fissions, are hypothesized to promote speciation by creating genetic incompatibilities between lineages. The research uses phylogenomic data and state-dependent birth-death models to analyze the impact of chromosomal changes on speciation rates across different clades of *Erebia*. Key findings include: 1. **Phylogenetic Resolution and Speciation Rates**: The study constructs a nearly fully resolved phylogeny of *Erebia* species, confirming the monophyly of major clades and estimating the age of the genus. The phylogeny reveals that chromosomal changes, both anagenetic (occurring within lineages) and cladogenetic (occurring at speciation events), are associated with higher speciation rates. 2. **Chromosomal Fusion and Fission Rates**: Anagenetic fusions occur at a higher rate than anagenetic fissions, but most speciation events in *Erebia* coincide with chromosomal changes, either through fusion or fission. Cladogenetic chromosomal fusion shows a higher degree of differentiation among clades, with rates ranging from 0.327 to 1.263 events per species per million years. 3. **Clade-Specific Analysis**: The study examines the impact of chromosomal changes on speciation rates within different clades of *Erebia*. Clades with higher karyotype diversity, such as the *tyndarus* clade, show higher rates of speciation related to chromosomal changes. Clades with lower karyotype diversity, like *ligea*, have a higher proportion of speciation unrelated to chromosomal changes. 4. **Model Validation and Interpretation**: The study validates the results using alternative models (ChromEvol) and assesses the impact of missing karyotype data. The findings are consistent across different models, suggesting the robustness of the conclusions. 5. **Discussion**: The study highlights that chromosomal speciation may be more relevant in clades with higher diversity in chromosome numbers. The high karyotype diversity and associated high speciation rates in the *tyndarus* clade are attributed to ecological factors, such as glacial cycles and population subdivisions. The study also discusses the potential mechanisms by which chromosomal fusions and fissions contribute to speciation, including the suppression of recombination and the buildup of reproductive isolation. Overall, the research provides evidence for the macroevolutionary impact of chromosomal rearrangements on speciation in *Erebia* butterflies, suggesting that these events play a significant role in the diversification of the genus.The study investigates the role of chromosomal fusion and fission in the macroevolutionary process of speciation in the genus *Erebia*, a group of butterflies with high karyotype diversity. Chromosomal rearrangements, particularly fusions and fissions, are hypothesized to promote speciation by creating genetic incompatibilities between lineages. The research uses phylogenomic data and state-dependent birth-death models to analyze the impact of chromosomal changes on speciation rates across different clades of *Erebia*. Key findings include: 1. **Phylogenetic Resolution and Speciation Rates**: The study constructs a nearly fully resolved phylogeny of *Erebia* species, confirming the monophyly of major clades and estimating the age of the genus. The phylogeny reveals that chromosomal changes, both anagenetic (occurring within lineages) and cladogenetic (occurring at speciation events), are associated with higher speciation rates. 2. **Chromosomal Fusion and Fission Rates**: Anagenetic fusions occur at a higher rate than anagenetic fissions, but most speciation events in *Erebia* coincide with chromosomal changes, either through fusion or fission. Cladogenetic chromosomal fusion shows a higher degree of differentiation among clades, with rates ranging from 0.327 to 1.263 events per species per million years. 3. **Clade-Specific Analysis**: The study examines the impact of chromosomal changes on speciation rates within different clades of *Erebia*. Clades with higher karyotype diversity, such as the *tyndarus* clade, show higher rates of speciation related to chromosomal changes. Clades with lower karyotype diversity, like *ligea*, have a higher proportion of speciation unrelated to chromosomal changes. 4. **Model Validation and Interpretation**: The study validates the results using alternative models (ChromEvol) and assesses the impact of missing karyotype data. The findings are consistent across different models, suggesting the robustness of the conclusions. 5. **Discussion**: The study highlights that chromosomal speciation may be more relevant in clades with higher diversity in chromosome numbers. The high karyotype diversity and associated high speciation rates in the *tyndarus* clade are attributed to ecological factors, such as glacial cycles and population subdivisions. The study also discusses the potential mechanisms by which chromosomal fusions and fissions contribute to speciation, including the suppression of recombination and the buildup of reproductive isolation. Overall, the research provides evidence for the macroevolutionary impact of chromosomal rearrangements on speciation in *Erebia* butterflies, suggesting that these events play a significant role in the diversification of the genus.