Khrystyna Kurta

1 Introduction One of the major challenges in evolutionary biology is to understand how species diversify into genetically distinct populations, subspecies and ultimately separate species (Coyne and Orr 2004; Grant and Grant 2020). As the Arctic ice caps receded at the end of the last glacial epoch, many species of salmonids colonised different freshwater systems across the Northern hemisphere.

Abstract Salmonids have a remarkable ability to form sympatric morphs after postglacial colonization of freshwater lakes. These morphs often exhibit differences in morphology, feeding, and spawning behaviour. Here we explore the genetics of morph differentiation by establishing a high-quality, annotated reference genome for the Arctic charr and use this as a resource for population genomic analysis of morphs from two Norwegian and two Icelandic lakes.

INTRODUCTION The salmonid Oncorhynchus mykiss, originally native to the Pacific basin of North America and the Kamchatka Peninsula in north-eastern Eurasia, has been introduced over the years in at least 99 countries (Stanković et al., 2015). Oncorhynchus mykiss, commonly known as steelhead trout (anadromous) and rainbow trout (spends its entire lifetime in fresh water) is one of the most domesticated and farmed aquaculture species worldwide (Teletchea & Fontaine, 2014).