An empirical test for convergence using African barbs (Cypriniformes: Cyprinidae)

Abstract

Evidence for convergence is often based on overall similarity as interpreted by human eyes. We use geometric morphometrics and an analysis of phylogenetic signal to determine if similarity in form between two sympatric species of cyprinid fishes in a community from the Dja River of Cameroon is due convergence or shared evolutionary history. The two species, Enteromiusaspilus and E.guirali, are deep-bodied and are very similar in color and appear to school together. The species co-occur with seven other species of Enteromius that have the more fusiform shape seen in other small barbs across Africa. Phylogenetic analysis of the mitochondrial cytochrome b and COI genes suggests that they are not sister taxa, and there is no phylogenetic signal when the phylogeny is overlaid on shape space. The convergence between the two is likely due to a variety of factors including predator avoidance and crypsis in open water, social mimicry to increase the benefit of the selfish herd effect, and increased protection of E.aspilus via Batesian mimicry of E.guirali, which has a protective dorsal spine.