Shallow population structure of southern bluefin tuna, Thunnus maccoyii (Castelnau, 1872) between Indian and Atlantic Oceans inferred from mitochondrial DNA sequences

Figures & data

Figure 1. Sampling locations of Thunnus maccoyii, which G1 and G2 indicate samples from the eastern Indian Ocean and the eastern Atlantic Ocean, respectively.

Figure 2. The phylogenetic tree based on the maximum-likelihood (ML) using Tamura-Nei model with 1000 bootstrap replications, for the combined mtDNA gene sequences (1240-bp) for T. maccoyii. G1 and G2 indicate samples from the estern Indian Ocean and the eastern Atlantic Ocean, respectively.

Table 1. mtDNA sequence variability in the cytochrome c oxidase subunit I (COI), control region (CR) and the combined genes for Thunnus maccoyii.

Locality	n	nh	COI		CR		The combined
			h	π	h	π	h	π
Indian Ocean	13	13	1.000 (±0.030)	0.002	1.000 (±0.030)	0.039	1.000 (±0.030)	0.020
Atlantic Ocean	24	24	1.000 (±0.012)	0.002	1.000 (±0.012)	0.033	1.000 (±0.012)	0.017

n indicates number of individuals; nh: number of haplotypes; h: haplotype diversity; π: nucleotide diversity.

Table 2. Analysis of molecular variance (AMOVA) results for the genetic structure of T. maccoyii based on the combined mtDNA sequence.

Source of variation	Variance	Percentage of variation	FST	p Value
Between clades	5.047	30.84	0.308	<0.001
Within clades	11.317	69.16

Table 3. Summary of the combined mtDNA sequence variability for two clades of T. maccoyii.

Clade	n	ti	tv	π	Tajima's D	Fu's FS	τ	θ0	θ1	Hri	SSD
A	28	104	19	0.017	−1.129	−12.659*	20.973	1.846	366.338	0.0085	0.0031
B	9	67	11	0.020	−0.651	−0.985	20.000	14.400	3794.991	0.0432	0.0248
Mean	18.5	85.5	15	0.019	−0.890	−6.822	20.486	8.123	2080.665	0.0258	0.0140

*Significant at p < 0.001.

n indicates number of individuals; ti: number of transitions; tv: number of transversions; π: nucleotide diversity; τ: moment estimator, θ₀ and θ₁: mismatch distribution parameter estimates; Hri: Harpending’s raggedness index; SSD: sum of squared differences from mismatch analyses.

Data availability statement

The data that support the findings of this study are openly available in [NCBI] at [https://www.ncbi.nlm.nih.gov/], reference number [MZ222168-MZ222241].