The average scores of p-distances at Co-1 and Cyt-b genes revealed a pattern of increased nucleotide diversity for four categories: (1) intraspecies, (2) intragenus, (3) intrafamily, and (4) intraorder. Scores for Co-1 genes were following: (1) 0.24 ± 0.19% (n = 66), (2) 1.54 ± 0.27% (n = 33), (3) 11.57 ± 0.24% (n = 42), and (4) 12.91 ± 0.16% (n = 102); while for Cyt-b genes, those values were (1) 1.92 ± 0.55% (n = 24), (2) 8.19 ± 0.09% (n = 812), (3) 15.42 ± 0.07% (n = 1573), and (4) 23.13 ± 0.19% (n = 211). A concordant increase in the distance score, as the rank of taxa grows, with the minimum at intraspecies level substantiates the concept that speciation in the order Scorpaeniformes mostly follows a geographic mode. Phylogenetic trees for 40 sequences of scorpionfish and four other fishes belonging to Actinopterigii were developed using Co-1 gene and four different analytical approaches: Bayesian, ML, MP, and NJ. Resolution of the Co-1 trees for the three genera that included different species branches was quite distinct in all approaches. Intrafamily branching for Cyt-b in Cottidae was also supported by all four kinds of trees but only for less numerous genera in the research.
Keywords: Co-1; Cyt-b; molecular phylogeny; nucleotide composition; p-distance; scorpionfish; sequence divergence; taxonomy.