Genetic relationships between and within some Malawian cichlid genera.

ABSTRACT

Genetic relationships were examined for a total of 90 individuals of 90 species or species var. from 13 genera of Malawian cichlids based on the sequences of an amplified 991-bp fragment of the mtDNA control region (mtDNA-CR). In the network analysis, no exclusive clades were made by all the members of any genera in this study. However, congeneric clades were observed by genera Buccochromis, Copadichromis, Protomelas, and Sciaenochromis, whereas no congeneric clades were observed by genera Mylochromis, Nimbochromis, and Otopharynx. In non-mbuna, an Aulonocara-Lethrinops group was divided into two groups, and the mean genetic distance of the larger group was much lower from mbuna than from other non-mbuna. Overall mean genetic distance within a genus was generally low in mbuna, whereas it was relatively high in non-mbuna. In the genetic tree of each genus, two or more large clades were observed, and some clades, such as those of Aulonocara hansbaenschi and Aulonocara nyassae in genus Aulonocara, Lethrinops micrentodon and Lethrinops sp. "gold harbor" in Lethrinops, and Otopharynx ovatus and Otopharynx brooksi in Otopharynx, were very deeply differentiated. Besides, a mbuna species, Pseudotropheus crabro, was extremely deeply differentiated from other members of this genus. These results suggest a widespread morphological convergence across the taxa in parallel with deep genetic differentiation in the long evolutionary story and some possibility of generation of the species of Aulonocara-Lethrinops group by hybridization of small non-mbuna and mbuna species. Furthermore, taxonomical reexamination is necessary based on a strong support by genetic connection.