Ecomorphological Diversification on Gill Arches in the Neotropical Superfamily Anostomoidea (Teleostei:Characiformes)

The hyper-abundant Neotropical freshwater fish superfamily, Anostomoidea contains two groups with seemingly disparate evolutionary strategies. The first group, the anostomids, represent ~150 species with a wide variety of body coloration, mouth position, tooth shape and trophic strategies ranging from generalist to herbivory to insectivory. The other major group, the families: curimatids, chilodontids and prochilodontids, contains around the same number of species but members are generally silvery with some pigmentation, have little variation in mouth position, possess reduced or no teeth and all feed mostly on detritus, or decaying organic matter and associated microorganisms. Although the detritivores may be superficially similar, there is substantial variation in the arrangement of the gill arches, which are used in processing food, within each family and even at the generic level. We investigate 1) how a group that presumably feeds on the same resource can exhibit similar species diversity to the Anostomidae, 2) if detritivore gill arches are more diverse than anostomids, 3) if detritivores are evolving gill arch morphology faster than the anostomids and 4) if there is convergence in morphologies. This system provides crucial information on the role of ecomorphology in diversification and whether detritivory encompasses a spectrum of morphological and ecological specialization.