Ecological and Evolutionary Consequences of Color- and Trophic Polymorphisms in Cichlid Fishes

12 benthic-limnetic axis and most populations are also color-polymorphic. The most comprehensive project focuses on the gold/dark color polymorphism in the Midas cichlid species complex (Amphilophus citrinellus spp.). Using a comparative approach that bases on extensive field collections of Midas cichlids, a substantial degree of ecological differentiation between color morphs is revealed. The differentiation is consistent throughout the species complex. From a common garden approach it is inferred, that eco-morphological differentiation between color morphs in the wild is likely partly genetically determined. This is an innovative finding in adaptive radiation research. The correlation of ecology and coloration presumably contributes to the maintenance of this color polymorphism over time through niche partitioning and additionally exhibits great potential to facilitate sympatric diversification processes, given the reported color assortative mating. In a subproject related to coloration, color differential predation by a major Midas cichlid predator (Parachromis managuensis) was revealed using color variants of the common Goldfish that are similar to gold and dark Midas cichlid color morphs. A highly increased attack risk was observed for the Goldfish variant that is similar to the Midas cichlid gold morph. The putative role of color differential predation in maintaining the color polymorphism throughout the evolutionary replicates is discussed. Another project aims at detecting intraspecific diversification along the benthic-limnetic axis in one of the youngest crater lakes of Nicaragua. In each of two older crater lakes multiple Midas cichlid species can be found, that are characteristically diverse along the benthic-limnetic axis. Substantial variability and individual specialization was found in this young Midas cichlid population. This may hint at the incipient evolution of a trophic resource polymorphism and possibly at imminent diversification along the benthic-limnetic axis. The second case study involved the scale eating cichlid Perissodus microlepis from Lake Tanganyika that is famous for its asymmetric mouth morphology. In some textbooks this species is referred to as an example of a stunning trophic specialization, and of the role of negative frequency-dependent selection in the maintenance of an intraspecific trophic polymorphism. Perissodus microlepis attacks its prey mostly from behind and snatches scales from the prey fish flanks. It is assumed that through the possession of asymmetric mouth morphologies scale-eating from the prey fish flanks is facilitated. So far, this trophic polymorphism has mainly been described as a dimorphic trait, i.e. left (L-morph) or right (R-morph) with no intermediate morphologies. It is thought that L-morphs prefer to attack the right flanks of their prey fish whereas R-