- What is the extent of variation within and between L. aeneus and L. kimberleyensis based on morphology, allozymes and mtDNA?
- Is there any evidence to indicate hybridisation between the two Orange River yellowfishes?
- Are there differences between populations of the same species in different parts of the Orange River system?
- Will current diversity patterns be affected by mixing of fishes from different tributary subsystems?
Paulette Bloomer1, I. Roger Bills2, F. Herman van der Bank3, Martin H. Villet4, Nick Jones2 and Gina Walsh3
1. Molecular Ecology and Evolution Programme, Dept. of Genetics, University of Pretoria;
- South AfricanInstitute for Aquatic Biodiversity, Grahamstown;
- Dept. of Zoology, University of Johannesburg,
- Dept. of Zoology, Rhodes University, Grahamstown
The relationships within and between two yellowfish species, Labeobarbus aeneus (smallmouth yellowfish) and L. kimberleyensis (largemouth yellowfish) from the Orange-Vaal system were investigated through three independently conducted studies of the same material collected from the Sak River (the type locality of L. aeneus), the upper Orange River at Aliwal North and the lower Orange River at Pella and Onseepkans.
Previously suggested body measures were used for field identification and this was followed by initial measurement of 53 features to investigate the morphological variation within and between the two species. This set of measurements was refined to 31 which were used for intensive analysis. There were consistent morphological differences between the two species from Aliwal North and the lower Orange.
Although the two species are closely related, these morphological differences presumably result from use of slightly different habitats and resources within the river. Thus L. kimberleyensis and L. aeneus are morphologically distinct and identifiable using several features e.g. mouth position, mouth size, eye to preopercular groove distance, colouration, interorbital width. Labeobarbus kimberleyensis specimens were morphologically similar in the upper and lower Orange sites. In contrast the two L. aeneus populations were
morphologically different from one another. The most obvious differences were that the lower Orange L. aeneus had significantly deeper bodies and longer fins. The lower Orange River, as well as being a much bigger river than the upper reaches at Aliwal North, provides a much wider variety of habitats which may account for the observed morphological variation.
http://www.fosaf.co.za/documents/Yellowfish follow up study report March 24.pdf
In association with the Yellowfish Working Group and with funding support from AngloGold Ashanti, FOSAF and the National Research Foundation.