Evolution of the ribosomal RNA internal transcribed spacer one (ITS-1) in cichlid fishes of the Lake Victoria region

The nucleotide sequences of the first internal transcribed spacer (ITS-1) o f the ribosomal RNA gene cluster have been determined for 11 species of clo sely related endemic cichlid fishes of the Lake Victoria region (LVR) and 6 related East African cichlids. The ITS-1 sequences confirmed independently derived basal phylogenies, but provide limited insight within this species flock. The line leading to Pseudocrenilabrus multicolor arose early, close to the divergence event that separated the tilapiine and haplochromine tri bes of the "African Group" of the family Cichlidae. In this phylogeny, Asta toreochromis alluaudi and the riverine Astatotilapia burtoni are sister tax a, which together are a sister group to a monophyletic assemblage including both Lake Victoria and Lake Edward taxa, The ITS-1 data support the monoph yly of haplochromine genera across lakes, Since Lake Victoria is believed t o have been dry between 14,500 and 12,400 BPE, the modern assemblage must h ave been derived from reinvasion by the products of earlier cladogenesis ev ents. Thus, although the regional superflock is monophyletic, the haplochro mines of Lake Victoria itself did not evolve in situ from a single ancestor . (C) 1999 Academic Press.