MITOCHONDRIAL-DNA DIVERSITY IN JACKASS MORWONG (NEMADACTYLUS-MACROPTERUS, TELEOSTEI) FROM AUSTRALIAN AND NEW-ZEALAND WATERS

The jackass morwong (Nemadactylus macropterus), a commercially valuabl e marine fish in the Australian - New Zealand region, was surveyed for genetic variation as part of a larger project aimed at clarifying its stock structure. Mitochondrial DNA variation in 166 jackass morwong f rom seven southern Australian localities was examined using nine restr iction enzymes. The 28 haplotypes identified gave an overall nucleon d iversity of 0.671. Mean nucleotide diversity per sample was 0.458%, wi th a (corrected) nucleotide divergence among samples of 0.001%. There was no significant spatial patterning. Five hundred individuals from e ight southern Australian localities and one New Zealand locality were examined using three restriction enzymes detecting polymorphic cut sit es. The 33 haplotypes identified gave an overall nucleon diversity of 0.635. Mean nucleotide diversity per sample was 1.247%, with a (correc ted) nucleotide divergence among samples of 0.002%. No differentiation was detected among the Australian localities. The New Zealand sample showed weak but significant divergence from the Australian samples. Th ese results were similar to those from a concurrent allozyme analysis, and we conclude that there is appreciable nuclear and mitochondrial D NA gene flow among Australian localities, while the Tasman Sea separat ing Australia from New Zealand acts as a partial barrier.