Clade II consisted of four deeply divergent subclades (9.0–11.8% nucleotide divergence for the control region 0.3–2.5% divergence at the cytochrome b locus). Strong allele-frequency differences were found between local populations in the south-western Pacific, both at the mitochondrial locus ( Φ st = 0.282–0.609) and at microsatellite loci ( = 0.202–0.313). northern Australia, West Papua, and the Coral Sea. Further phylogeographic partition was evident between the western IMPA and the regions sampled east and south of it, i.e. Such a high level of genetic divergence suggested the occurrence of two sister species.
All haplotypes sampled from the Indo-Malay-Papua archipelago (IMPA) and the south-western Pacific coalesced into a clade (clade II) that was deeply separated (14.5% nucleotide divergence) from a clade grouping all haplotypes from the Persian Gulf and Oman Sea (clade I). commerson across the Indo-West Pacific range using control-region sequences (including previously published data sets), cytochrome b gene partial sequences, and eight microsatellite loci, to further explore its phylogeographic structure. We investigated the genetic composition of S. One such exception is the narrow-barred Spanish mackerel ( Scomberomorus commerson Lacepède, 1800), where strong genetic heterogeneity at the regional scale has been previously reported. Although migratory pelagic fishes generally exhibit little geographic differentiation across oceans, as expected from their life history (broadcast spawning, pelagic larval life, swimming ability of adults) and the assumed homogeneity of the pelagic habitat, exceptions to the rule deserve scrutiny.