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

2004; Taylor & Francis; Volume: 34; Issue: 1 Linguagem: Inglês

10.1080/03014223.2004.9517762

1175-8899

R. M. McDowall, Jonathan M. Waters,

Fish Biology and Ecology Studies

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 relationshipssexual dimorphismbiogeography Notes National Institute of Water and Atmospheric Research, P.O. Box 8602, Christchurch, New Zealand. Email: r.mcdowall@niwz.co.nz Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand.