One of the most compelling features of the cichlid fishes of the African Great Lakes
is the seemingly endless diversity of male coloration. Colour diversification has been
implicated as an important factor driving cichlid speciation. Colour has also been central
to cichlid taxonomy and, thus, to our concept of species diversity. We undertook a
phylogeographical examination of several allopatric populations of the Lake Malawi cichlid
Pseudotropheus zebra in order to reconstruct the evolutionary history of the populations,
which exhibit one of two dorsal fin colours. We present evidence that populations with red
dorsal fins (RT) are not monophyletic. The RT population defining the northern limit of the
distribution has evidently originated independently of the southern RT populations, which
share a common ancestry. This evidence of species-level colour convergence is an important
discovery in our understanding of cichlid evolution. It implies that divergence in coloration
may accompany speciation, and that allopatric populations with similar coloration cannot be
assumed to be conspecific. In addition to this finding, we have observed evidence for
introgression, contributing to current evidence that this phenomenon may be extremely
widespread. Thus, in species-level phylogenetic reconstructions, including our own,
consideration must be given to the potential effects of introgression.