Trophic evolution in African citharinoid fishes (Teleostei: Characiformes) and the origin of intraordinal pterygophagy.

The African freshwater suborder Citharinoidei (Characiformes) includes 110 species that exhibit a diversity of feeding modes comparable to those characteristic of more speciose groups such its sister, the Characoidei (2000+ species) or the distantly related Cichlidae (1600+ species). Feeding habits of the Citharinoidei range from generalist omnivores to highly specialized feeding modes including ectoparasitic fin-eating, i.e. pterygophagy. We examine diet preference evolution in the Citharinoidei using newly inferred multi-gene-based hypotheses of phylogenetic relationships for representatives of 12 of the 15 genera in the suborder. Ancestral character state reconstructions onto our best tree indicate that the three most-generalist diets - pelophage/planktivore, omnivore and invertivore - are also the most primitive conditions within the Citharinoidei. The feeding mode of the most recent common ancestor of the Citharinoidei was characterized by high uncertainty. The more specialized feeding habits - herbivory, piscivory and pterygophagy - originated later in the Citharinoidei, likely from invertivore ancestors and possibly across a short time period. Highly specialized fin eaters (Belonophago, Phago and Eugnatichthys) share a common origin along with a strict piscivore (Mesoborus) and an invertivore (Microstomatichthyoborus). The largely piscivorous, but facultative fin eater, Ichthyborus is not exclusively related to them. Our results demonstrate that overall diet preference transitions in the Citharinoidei were rare events with very few reversals or parallelisms, and that evolutionary shifts in trophic ecology have not played a major role in intraordinal diversification. This situation contrasts with other groups in which dietary transitions have played key roles in species diversification.