The squeaker catfishes or Synodontis of Lake Tanganyika evolved from a single common ancestor, according to a study on the molecular phylogeny of the group published in a recent issue of the Journal of Evolutionary Biology.
Julia Day, Roger Bills and John Friel analysed 1697 base-pair sequences consisting of nuclear (ribosomal protein-codin gene S7), mitochondrial (cytochrome b) and transfer RNA gene fragments in 65 samples (representing about 40 species) of squeaker catfishes to study the evolutionary relationships of the group.
The authors recovered a single origin for the Lake Tanganyika species flock and found that these species have evolved within the last 5.5 million years. This makes them relatively recent inhabitants of the lake (thought to be 9"12 million years old).
The authors also recovered a monophyletic group of southern African riverine species that appeared to have diversified very rapidly (within the last 890,000 years).
This group, like the southern African riverine serranochromine cichlids, was thought to have been the result of adaptive radiation within a now extinct lake (Makgadikgadi).
For more information, see the paper: Day, JJ, R Bills & JP Friel (2009) Lacustrine radiations in African Synodontis catfish. Journal of Evolutionary Biology 22, pp. 805"817.