Abstract
The availability of diverse ecological niches can promote adaptation of trophic specializations and related traits, as has been repeatedly observed in evolutionary radiations of freshwater fish. The role of genetics, environment, and history in ecologically driven divergence and adaptation, can be studied on adaptive radiations or populations showing ecological polymorphism. Salmonids, especially the Salvelinus genus, are renowned for both phenotypic diversity and polymorphism. Arctic charr (Salvelinus alpinus) invaded Icelandic streams during the glacial retreat (about 10,000 years ago) and exhibits many instances of sympatric polymorphism. Particularly, well studied are the four morphs in Lake Þingvallavatn in Iceland. The small benthic (SB), large benthic (LB), planktivorous (PL), and piscivorous (PI) charr differ in many regards, including size, form, and life history traits. To investigate relatedness and genomic differentiation between morphs, we identified variable sites from RNA‐sequencing data from three of those morphs and verified 22 variants in population samples. The data reveal genetic differences between the morphs, with the two benthic morphs being more similar and the PL‐charr more genetically different. The markers with high differentiation map to all linkage groups, suggesting ancient and pervasive genetic separation of these three morphs. Furthermore, GO analyses suggest differences in collagen metabolism, odontogenesis, and sensory systems between PL‐charr and the benthic morphs. Genotyping in population samples from all four morphs confirms the genetic separation and indicates that the PI‐charr are less genetically distinct than the other three morphs. The genetic separation of the other three morphs indicates certain degree of reproductive isolation. The extent of gene flow between the morphs and the nature of reproductive barriers between them remain to be elucidated.
Highlights
Organismal diversity reflects the process of evolution and highlights the importance of natural selection in building and maintaining adaptations (Darwin, 1859)
Feeding is a primary function in all animals and in nature, we see many examples of spectacular adaptive radiation where natural selection has generated a range of adaptations in specific feeding structures and foraging behavior (Losos & Ricklefs, 2009; Seehausen & Wagner, 2014)
The genomics revolution has spawned powerful tools for studying relatedness of populations and species, the connections between genetic and phenotypic variation, for example, how variations in the form of feeding structures are caused by differential expression of key developmental genes (Abzhanov et al, 2006; Guðbrandsson et al, 2018), and to determine to what extent these differences are due to genetic differences
Summary
Organismal diversity reflects the process of evolution and highlights the importance of natural selection in building and maintaining adaptations (Darwin, 1859). The genomics revolution has spawned powerful tools for studying relatedness of populations and species, the connections between genetic and phenotypic variation, for example, how variations in the form of feeding structures are caused by differential expression of key developmental genes (Abzhanov et al, 2006; Guðbrandsson et al, 2018), and to determine to what extent these differences are due to genetic differences (and how they are distributed in genomes; Wolf & Ellegren, 2016) These methods have enabled studies evaluating feedback between the organism and its environment, the role of plasticity in generating functional variation and possibly promoting adaptation (Abouheif et al, 2014; Morris & Rogers, 2014). The data enabled analyses of the genetic separation of three of the sympatric morphs, the origin of the rare piscivorous charr, the genomic patterns of differentiation between morphs and the genes and molecular systems that may associate with their specializations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
