Journal of the Royal Society of New Zealand abstracts

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Phylogenetic relationships in a small group of diminutive galaxiid fishes and the evolution of sexual dimorphism

R. M. McDowall

National Institute of Water and Atmospheric Research,
P.O. Box 8602, Christchurch, New Zealand.
Email: r.mcdowall@niwz.co.nz

J. M. Waters

Department of Zoology, University of Otago,
P.O. Box 56, Dunedin, New Zealand.

Abstract  Analysis of diverse morphological characters supports combined monophyly of the diminutive galaxiid genera Brachygalaxias (Chile) and Galaxiella (Australia), both of which are monophyletic. However, equally parsimonious trees vary in the suggested relationships among the three species of Galaxiella, and in no instance is there strong support for any particular association among them. The African Galaxias zebratus may also form a monophyletic clade when added to [Brachygalaxias + Galaxiella], though character analyses that include a wider representation among galaxiids are needed to clarify that question. Brachygalaxias and Galaxiella are distinctive among all galaxiids in having longitudinal coloration, including bright yellow to orange stripes. Brachygalaxias gothei is not sexually dimorphic (orange stripes are present in both sexes), whereas among Galaxiella species, the eastern Australian G. pusilla is dimorphic (only the smaller male has bright red stripes). The western Australian G. nigrostriata may also be dimorphic (males are sometimes described as having more vivid stripes than females), but it seems less likely in G. munda. Retention of what seems to be a juvenile character in Galaxiella, in G. munda, may suggest that it is a neotenous derivative of another Galaxiella species. Known morphological characters do not identify the sister species of G. munda, though on zoogeographic grounds it is perhaps more likely to share closest ancestry with G. nigrostriata.

Keywords  Galaxiidae; Brachygalaxias; Galaxiella; phylogenetic relationships; sexual dimorphism; biogeography

R03004; Online publication date 11 March 2004; Received 4 April 2003; accepted 4 December 2003
© Journal of the Royal Society of New Zealand, Volume 34, Number 1, March 2004, pp 23-57

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