Mitochondrial Genomic Analysis of the Percomorph Fish Phytogenies : Resolving Polytomies Using Large Datasets

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A series of recent molecular phylogenetic studies based on whole mitochondrial genome (mitogenome) sequences (Inoue et al.,2003a, b, 2004 ; Ishiguro, Miya & Nishida,2003 ; Miya et al., 2003 ; Saitoh et al., 2003), however, have shed a new light on our concepts of actinopterygian higher-level relationships. These six mitogenomic studies plus previous pioneering works (Chang, Huang & Lo, 1994 ; Johansen & Bakke, 1996,Miya & Nishida,1999,2000b ; Noack, Zardoya & Meyer,1996 ; Saitoh et al., 2000 ; Tzeng et al., 1992 ; Zardoya, Garrido-Pertierra & Bautista,1995) together sampled all major lineages of actinopterygians at the ordinal level, with their data sets partially overlapping each other. Also they were all based on the same sets of strictly homologous characters, with no potential for paralogous comparisons among sampled genes owing to ancient genome duplication (Martin & Burg,2002) as recently suggested for actinopterygian nuclear genomes (e.g., Taylor et al., 2003 ; Van de Peer, Tayl … More or & Meyer,2003). In addition, it should be noted that the resultant phylogenies were well resolved and many basal clades received high statistical support irrespective of analytical methods (see Simmons & Miya, 2004). Accordingly the whole mitogenome sequences have afforded a new comprehensive perspective on the higher-level relationships of actinopterygians, portions of which have been supported by recent molecular phylogenetic studies based on different markers (Chen, Bonillo & Lecointre,2003 ; Wiley, Johnson & Dimmick,2000). Exception to this is relationships of the Percomorpha, known as "bush at the top of the tree"(Nelson, 1989).In this study, I attempted at resolving relationships of the Percomorpha based on the whole mitochondrial genome sequences. First I successfully demonstrated a phylogenetic position of toadfish (order Batrachoidiformes) using whole mitochondrial genome sequences from 102 actinopterygians (Miya et al., 2005). I am further analyzing large datasets comprising 336 actinopterygians to correctly determine limits of the Percomorpha and resolve their intrarelationships. The analyses have been conducted using two parallel computing systems and will be finished within this year. Less