The 'Barbus' intermedius species flock of Lake Tana (Ethiopia) I - The ecological and evolutionary significance of morphological diversity

Abstract The Lake Tana (northern Ethiopia) ichthyofauna is dominated by ‘large’ barbs (Barbus spp., Cyprinidae). Recently, fourteen Bar‐bus morphs have been described. This paper provides evidence that these morphs are indeed biological species. To investigate the hypothesis that disruptive selection on feeding‐related morphological characters was the evolutionary driving force of speci‐ation, an ecomorphological analysis, investigating the quantitative relationships between morphology and feeding abilities on a number of aquatic food types was investigated. The analysis accurately predicted the potential trophic niches of the Lake Tana barbs and supported the disruptive selection hypothesis. Finally, a hypothetical evolutionary scenario is presented in which disruptive selection led to initial morphological differentiation, and spatial and temporal spawning segregation stabilized the genetic differences among the morphs, resulting in speciation.