Parallel evolution in ichthyophagous annual killifishes of South America and Africa
Morphological characters of two lineages of aplocheiloid annual killifishes containing predatory species feeding on sympatric congeners were analysed under a phylogenetic framework. They are the South American rivulid genus Austrolebias and the African nothobranchiid genus Nothobranchius. Independent phylogenetic analyses of morpho- logical characters indicated several apomorphic conditions homoplastically occurring in ichthyophagous species of both genera. These character state transformations may be related to the evolution of ichthyophagous habits. Eleven of these convergent characters are concentrated on the head bones, including jaw suspensorium, jaws and neurocranium. Besides the parallel occurrence of long jaws, convergent transformations involve widening of bone parts, which serve as support to muscles responsible for closing the jaws or retraction and expansion of the mouth cavity. The distribution of the homoplas- tic conditions among terminal taxa of the two annual fish groups indicates that similar characters states arose at different points of the evolutionary history of South American and African killifishes, with most transformations being gradually acquired along more inclusive clades.