Sequence diversity at cytochrome oxidase 1 (Co-1) gene among sculpins (Scorpaeniformes, Cottidae) and some other scorpionfish of Russia Far East with phylogenetic and taxonomic insights

Abstract

Mitochondrial DNA (mtDNA) atCo-1 gene region was sequenced for 7 scorpion fish species (in total, 16 sequences of at least 552 bp) from the Far East of Russia and compared with 15 other sequences of Scorpaeniformes comprising altogether 29 scorpion-like fish sequences and two outgroup sequences (Cypriniformes). The analysis of the protein-codingCo-1 gene revealed statistically substantiated bias in the (T+C) ∶ (A+G) content, proving basic findings. The average scores ofp-distances for different scales of the evolutionary history atCo-1 gene revealed a clear pattern of increased nucleotide diversity at four different levels: (1) intraspecies, (2) intragenus, (3) intrafamily, and (4) intraorder. The scores of averagep-distances for the compared fish groups were: (1) 1.00±0.20%, (2) 3.80±0.20%, (3) 12.40±1.20%, and (4) 18.00±0.38%, respectively (mean±SE). These data support the concept that speciation in the order Scorpaeniformes, in most cases, follows a geographic mode through accumulation of numerous small genetic changes over a long period of time. However, intraspecies diversity was surprisingly high among scorpionfish. Phylogenetic trees for 29 sequences of scorpionfish and 2 other fishes belonging to ray-finned fishes (Actinopterigii) were developed usingCo-1 gene and four different analytical approaches: Bayesian (BA), maximum likelihood (ML), neighbour-joining (NJ), and maximum parsimony (MP). The analysis revealed a monophyletic origin for the representatives of Cottidae, which is the principal scorpionfish family investigated (100, 96, 98% support level in our BA, MP, and NJ analyses). Similarly, the monophyletic origin of up to the three compared scorpion-like fish genera was supported by molecular phylogenetic data. Species identification on individual basis (barcoding tagging) was high. A few taxonomic complications arose during the analysis and they are discussed here in.