The Victoria Falls, a species boundary for the Zambezi Parrotfish, Cyphomyrus discorhynchus (Peters, 1852), and the resurrection of Cyphomyrus cubangoensis (Pellegrin, 1936) (Mormyridae: Teleostei)

Abstract

Cyphomyrus discorhynchus occurs in the Zambezi River and in the linked systems of the Kwando and the Okavango. We collected specimens from both above and below the Victoria Falls and recorded Electric Organ Discharges. We found a marked degree of anatomical differentiation among the specimens from the Zambezi delta to the Victoria Falls that represents a subspecific, geographical cline, reflecting the great length (1400 km) and high ecological diversity of that river section (Lower and Middle Zambezi). We confirm that the populations above the Falls (i.e. Upper Zambezi, Kwando and Okavango) are differentiated from those below, possessing fewer dorsal fin rays (a median of 30–31 rather than 33–34). The waveforms of the electric organ discharge pulses have four phases and show geographic variation but were briefer for specimens from below the Falls. We resurrect Cyphomyrus cubangoensis (Pellegrin, 1936) for the Upper Zambezi/Kwando/Okavango system.

Keywords:

• allopatric speciation
• parapatric
• geographic cline
• electric organ discharges
• southern Africa

Acknowledgements

The curators and staff of the following collections and institutions are thanked for granting specimens for anatomical comparisons to be made: South African Institute for Aquatic Biodiversity (SAIAB), Zoologische Staatssammlung München (Bavarian State Collection, Munich: ZSM), British Museum of Natural History (BMNH), Naturhistorisches Museum Basel (NMB), Muséum d'Histoire Naturelle de la Ville de Genève (MHNG), Muséum Royal de l'Afrique Centrale (MRAC). We are grateful to Paul Skelton for anatomical advice and general support, and to Roger Bills for support with accessioning and collection material. We gratefully acknowledge the constructive criticism from two anonymous referees. The Regensburg morphology team comprised Ellen Fröhlich, Silvia Förster, Peter Machnik, Birgit Blaul, Sabine Hartl, Susanne Füssel, Lena Dietz, Andreas Lechner and Henriette Seichert. This work was supported by the Deutsche Forschungsgemeinschaft (DFG, grant nos (KR446/10 to KR446/12).