Figure 1. Character-based key for all species of tunas (Thunnus) derived from 87 reference sequences [49], [53] constituting 14 nucleotides.

Numbers in brackets indicate the number of individual sequences. Nucleotide positions are numbered following Ward et al.'s [49] sequences. Simple pure characteristic attributes (CAs; highlighted) identify longtail (T. tonggol; LON), northern bluefin (T. thynnus; NBF), and southern bluefin (T. maccoyii; SBF) tuna. Simple private CAs (underlined) diagnose bigeye tuna (T. obesus; BET). Compound pure CAs diagnose yellowfin tuna (T. albacares; YFT), blackfin tuna (T. atlanticus; BLK), albacore (T. alalunga; ALB), and Pacific bluefin tuna (T. orientalis; PBF). Though albacore mtDNA has introgressed into the Pacific bluefin tuna mitogenome, compound pure CAs can differentiate these species (boxed).