Mynstur í sérhæfingu fæðuöflunarfæra bleikjuafbrigða

Specialization to a particular niche can be a key mechanism driving adaptive divergence and the early stages of speciation. Polymorphic Arctic charr (Salvelinus alpinus) are known to exhibit morphologies related to distinct feeding strategies, yet the evolutionary processes shaping this variation and its contribution to ecological divergence remain poorly understood. In this thesis, craniofacial anatomy and bone shape in Arctic charr are quantified and analyzed in ecological and evolutionary contexts. Arctic charr were sampled across Iceland, as well as Brown trout (Salmo trutta), here representing an evolutionary outgroup. Linear measures and 2D landmarks were derived from internal and external craniofacial anatomy, using the Ecological Survey of Icelandic Lakes database and newly collected specimens. Variation in shape was studied across populations and species. The results show benthic-pelagic separation in shape in Arctic charr morphs. Using Brown trout as an outgroup indicated that the Arctic charr populations were specializing towards benthism. Icelandic Arctic charr show high variation in shape across populations, however allometry of shape traits was found to be more conserved. These results demonstrate that ecological niche specialization can drive morphological divergence within a single population and across populations, highlighting the role of trophic adaptation in the early stages of divergent evolution in fish.