Journal of the Royal Society of New Zealand abstracts
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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