| Summary: | The Arctic charr Salvelinus alpinus is extremely diverse and its differentiation may indicate ecological speciation. This dissertation aims to compare trends in ecological diversity across broad geographical regions and place it within an ecosystem context by comparing study systems in Iceland and Alaska. In the first chapter, gut contents of Arctic charr across ~50 lakes in Iceland were analyzed to form 6 habitat-associated prey categories. Consumption of zooplankton was related to high silicon dioxide and low nutrient concentrations in the lake. Snail, tadpole shrimp, pea clam, and fish consumption were related to lake altitude, depth, and brown trout abundance. In the second chapter, the relationship between morphology and consumption within each prey category is analyzed. In the third chapter, methods are developed to detect polymorphism through the presence of multiple growth curves within populations using mixture models. Random forest models indicated that polymorphism was more likely to occur in lakes with low brown trout abundance, high altitude, and conditions with high zooplankton and fish consumption. The fourth chapter analyzes morphological variation in 4 lakes in southwestern Alaska. Two forms were found to coexist in Lower Tazimina Lake. Finally, food webs are analyzed in the fifth chapter using stable isotope ratios of fish fauna across 11 lakes in Iceland and 4 lakes in Alaska. Limnetic carbon use and piscivory appears dependent on morphological differentiation and the presence of competitors. Bleikja Salvelinus alpinus er fjölbreytt tegund þar sem stofnaaðskilnaður getur bent til vistfræðilegrar tegundamyndunar. Markmið ritgerðarinnar var að skoða tilhneigingar í vistfræðilegum fjölbreytileika í tengslum við vistkerfi. Þetta var gert á stóru landsvæði með samanburði milli Íslands og Alaska. Í fyrsta kafla var fæða bleikju úr u.þ.b. 50 vötnum skoðuð. Fengust 6 fæðuhópar sem tengja mátti búsvæðum. Fæðunámi á svifdýrum tengdist auknu magni silikon dioxíðs og litlu næringarefnaframboðiu. Át á ...
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