We studied the phylogenetic relationships of Otiteselline fig wasps associated with Ficus in the Afrotropical region using rDNA sequences. African fig species usually host two species of Otiteselline fig wasps. Phylogenetic analyses reveal that this pattern of association results from the radiation of two clades of wasps superimposed on the fig system. Within each clade, wasp species generally cluster according to their host classification. The phylogenies of the two clades are also generally more congruent than expected by chance. Together these results suggest that Otiteselline wasp speciation is largely constrained by the diversification of their hosts. Finally, we show a difference in ovipositor length between the two Otiteselline species coexisting in the same Ficus species, which probably corresponds to ecological differences. The diversification of ecological niches within the fig is probably, with cospeciation, one of the key factors explaining the diversification and maintenance of species of parasites of the fig/pollinator system.