Annotated genes were used as input to compare chromosomes within a genome or across genomes. First, we performed a mutual search of protein sequences for potential homologous genes by BLASTP software. And we set stringent parameters e values <1e-5 and scores >100. Some uncertainties could be excluded by the set stringent parameters. Next, information on homologous genes was used as input and collinearity of homologous gene pairs was located by using ColinearScan and McScanX software. The Ks of collinear gene pairs was calculated by the Nei–Gojobori approach implementing the Bioperl statistical module (https://bioperl.org).