PHYLOGENY OF AFRICAN CICHLID FISHES AS REVEALED BY MOLECULAR MARKERS

The species flocks of cichlid fish in the three great East African Lak es, Victoria, Malawi, and Tanganyika, have arisen in each lake by expl osive adaptive radiation. Various questions concerning their phylogeny have not yet been answered. In particular, the identity of the ancest ral founder species and the monophyletic origin of the haplochromine c ichlids from the East African lakes have not been established conclusi vely. In the present study, we used the anonymous nuclear DNA marker D XTU1 as a step towards answering these questions. A 280 bp-fragment of the DXTU1 locus was amplified by the polymerase chain reaction from E ast African lacustrine species, the East African riverine cichlid spec ies Haplochromis bloyeti, H. burtoni and H. sparsidens, and other Afri can cichlids. Sequencing revealed several indels and substitutions tha t were used as cladistically informative markers to support a phylogen etic tree constructed by the neighbor-joining method. The topology, al though not supported by high bootstrap values, corresponds well to the geographical distribution and previous classification of the cichlids . Markers could be defined that: (i) differentiate East African from W est African cichlids; (ii) distinguish the riverine and Lake Victoria/ Malawi haplochromines from Lake Tanganyika cichlids; and (iii) indicat e the existence of a monophyletic Lake Victoria cichlid superflock whi ch includes haplochromines from satellite lakes and East African river s. In order to resolve further the relationship of East African riveri ne and lacustrine species, mtDNA cytochrome b and control region segme nts were sequenced. The mtDNB-based trees support the notion of the mo nophyly of the Lake Victoria superflock but are ambigious with respect to the phylogenetic position of the Lake Malawi flock.