3.4 Genome evolution
To better understand the evolutionary history of C. undulatus , we identified single-copy orthologs by clustering homologous gene sequences from L. bergylta , S. melops , O. niloticus , A. percula , D. rerio , S. anshuiensis , C. semilaevis ,G. aculeatus , O. latipes , B. pectinirostris ,L. maculates , T. rubripes , and C. milii . As a result, 619 single-copy genes and 22,286 genes from 15,410 families were identified in C. undulatus (Fig. 6A). Next, we used the coding sequences of 619 single-copy genes to construct a phylogenetic tree and determine divergence times. According to the phylogenetic analysis,C. undulatus was clustered together with S. melops andL. bergylta , belonging to the Labrida family. C. undulatusdiverged from the common ancestor with G. aculeatus and L. maculates around 92.28 Mya (Fig. 6B). Our results are consistent with major percomorph subclade (Labrida family included) diversification, which occurred approximately 85-100 Mya in the Late Cretaceous period (Alfaro et al. 2018). C. undulatus diverged from the common ancestor with L. bergylta and S. melops around 58.37 Mya. This calibration time is believed to be the initial diversification of Labridae; subsequently, the pharyngeal jaw accelerated adaptive radiation of the Labrid ecomorphological diversity (Alfaro et al. 2009).