Fig. 2

The distinctive patterns of the Z chromosome in rearrangement and gene evolution. A There are a total of 31 points, with each ancestral chromosome corresponding to a single point. The Z chromosome is marked with red, and the dotted line marks its position relative to the autosomes. The x-axis is the number of genes an ancestral chromosome contains, and the y-axis is the number of fusions that have occurred independently in the evolutionary history of the ancestral chromosome. There was a negative correlation (Pearson’s product-moment correlation, P < 0.001) between the number of fusion events and the gene number of ancestral chromosomes. B There are a total of 31 points, with each ancestral chromosome corresponding to a single point. The Z chromosome is marked with red, and the dotted line marks its position relative to the autosomes. The x-axis is the number of genes an ancestral chromosome contains, and the y-axis is the number of fissions that have occurred independently in the evolutionary history of the ancestral chromosome. There was a positive correlation (Pearson’s product-moment correlation, P < 0.001) between the number of fission events and the gene number of ancestral chromosomes. C There are a total of 62 points, with each ancestral chromosome corresponding to two points. The Z chromosome is marked with red, and the dotted line marks its position relative to the autosomes. The x-axis is 31 ancestral chromosomes, and the y-axis is the average number of loss or duplication events per gene of an ancestral chromosome. The gene loss events are marked in brown, and the gene duplication events are marked in green. D The boxplot shows that the length of extant Z chromosomes is significantly (Wilcoxon rank-sum test “greater”; P < 0.001) higher than that of the extant autosome. E The boxplot shows that the GC content of extant Z chromosomes is significantly (Wilcoxon rank-sum test “greater”; P < 0.001) higher than that on the extant autosome. F The boxplot shows that the number of genes of extant Z chromosomes is significantly (Wilcoxon rank-sum test “greater”; P < 0.001) higher than that on the extant autosome. G The boxplot shows that the number of lineage-specific genes on extant Z chromosomes is significantly (Wilcoxon rank-sum test “greater”; P < 0.001) higher than that on the extant autosome. H The boxplot shows that the proportion of lineage-specific genes of extant Z chromosomes is significantly (Wilcoxon rank-sum test “greater”; P < 0.001) higher than that on the extant autosome