Adaptive Significance of Intra- and Interspecific Differences in the Feeding Repertoires of Cichlid Fishes

Abstract

Intraspecific modulatory multiplicity in the feeding mechanism of cichlids as elucidated by electromyography has profound implications on small-scale trophic events the sum of which is the very core of such large-scale population and evolutionary phenomena as efficiency of trophic exploitation niche width and overlap competition and adaptation. The greatest paradox emerging from the study on intra and interspecific differences in feeding repertoires of cichlid fishes is that the most specialized taxa are not only remarkable specialists in a narrow sense but also jacks-of-all-trades. If specialists are simultaneously jacks of-all-trades how could they have evolved according to the widely accepted hypothesis that broadening the range of usable resources prevents species from specializing on individual types? The organism can be considered to be composed of structural elements and functional components that exert mutual influences. As a result, a network of interacting constraints is set up. The nature of the network determines the direction and range of evolutionary changes the possibilities of optimizing adaptations and built-in variability of the trait. A change in the network can put a static trait into a different context to become dynamic. These changes in variability due to changes in the structure of the network cannot be explained in terms of simple adaptation to the external environment. Fitness is considered to depend on the nature of a network of interacting constraints. The possibilities of optimization the sensitivity of the phenotypic traits to environmental differences and the correlated evolutionary responses of different traits are all related to this network of interacting constraints between the elements and components of the organism. Thus the experimental and comparative studies of these networks of interacting constraints should become an increasingly more important focus for morphologists as they attempt to refine their understanding of adaptation.