Genetic divergence of Octopus vulgaris species in the eastern Mediterranean

Nucleotide divergence in cytochrome c oxidase subunit I (COI) gene of mitochondrial DNA was analyzed to determine interpopulational variation of common octopus (Octopus vulgaris) species sampled along eastern Mediterranean. Nucleotide composition and nucleotide pair frequency analyses of 440 individuals representing 11 populations were investigated. Estimation of evolutionary divergence between sequences was conducted using Tamura-Nei model. Considering 440 individuals, 35 (5%) variable sites and an average variation of 1.9% were found between specimens. Highest divergence was found between Med11 and Med04-Med07 populations; with a genetic distance value of 0.039 (3.9%). Estimation of transition/transversion bias (R) was made under the Tamura-Nei model and resulted as 2.32. Phylogenetic tree was constructed using four methods: neighbor joining (NJ), minimum evolution (ME), maximum likelihood (ML) and unweighted pair-group method of arithmetic average (UPGMA). Results from clustering patterns of the consensus tree, with the sum of branch length = 0.05189, pointed out a correlation between genetic and geographic distance.