https:\/\/onlinelibrary.wiley.com\/doi\/10.1111\/mec.70085<\/p>\n
ABSTRACT<\/h2>\n\nSalmonids have a remarkable ability to form sympatric morphs after postglacial colonisation of freshwater lakes. These morphs often differ in morphology, feeding and spawning behaviour. Here, we explored the genetic basis of morph differentiation in Arctic charr (n<\/i>\u2009=\u2009283) by first establishing a high-quality reference genome and then using this in whole genome sequencing of distinct morphs present in two Norwegian and two Icelandic lakes. The four lakes represent the spectrum of genetic differentiation between morphs from one lake with no genetic differentiation between morphs, implying phenotypic plasticity, to two lakes with locus-specific genetic differentiation, implying incomplete reproductive isolation, and one lake with strong genome-wide divergence consistent with complete reproductive isolation. As many as 12 putative inversions ranging from 0.45 to 3.25 Mbp in size segregated among the four morphs present in one lake, Thingvallavatn, and these contributed significantly to the genetic differentiation among morphs. None of the putative inversions were found in any of the other lakes, but there were cases of partial haplotype sharing in similar morph contrasts in other lakes. Our findings are consistent with a highly polygenic basis of morph differentiation with population-specific selection on alleles linked to the development of similar morph phenotypes. The results support a model where morph differentiation is first established through phenotypic plasticity, leading to niche expansion and separation. This may be followed by gradual development of reproductive isolation, locus-specific differentiation and eventually complete reproductive isolation and genome-wide divergence.<\/p>\nFIGURE 4![\"\"](\"https:\/\/uni.hi.is\/apalsson\/files\/2025\/08\/mec70085-fig-0004-m-214x300.jpg\")
<\/a><\/strong><\/div>\nGenetic differentiation between small and large benthivorous morphs of Arctic charr in Thingvallavatn. (a) Genome scan based on estimated allele frequencies for individual SNPs. Gene annotations are shown for the top 0.001% of significant SNPs at putative inversions marked by stars. (b\u2013e) Zoom-in profile of four putative inversion regions in (a). Top panel: Linkage disequilibrium (LD), measured as r<\/i>2<\/sup>, between the top significantly associated SNP and surrounding variants; bottom panel: Pairwise LD (r<\/i>2<\/sup>) among all genotypes within each region, including the following genomic regions (b) Scaffold 4: 75.25\u201376.13\u2009Mb, (c) Scaffold 5: 22.30\u201322.75\u2009Mb, (d) Scaffold 9: 61.30\u201362.11\u2009Mb and (e) Scaffold 17: 32.45\u201333.20\u2009Mb. The horizontal red and blue lines indicate Bonferroni corrected significance thresholds with significance levels \u03b1\u2009=<\/i>\u200910\u22123<\/sup> and \u03b1\u2009=<\/i>\u200910\u22128<\/sup>, respectively, after taking into account that 107<\/sup> SNPs were used. (f) Wilcoxon rank test of theta (\u03b8, nucleotide diversity) distributions across the genome and within putative inversion regions. Significance levels: *p<\/i>\u2009<\u20090.05, **p<\/i>\u2009<\u20090.01, ***p<\/i>\u2009<\u20090.001, ns indicates p<\/i>\u2009>\u20090.05.<\/div>\n<\/div>\n<\/p>","protected":false},"excerpt":{"rendered":"
Now published in Molecular Ecology Whole genome sequencing reveals how plasticity and genetic differentiation underlie sympatric morphs of Arctic charr. https:\/\/onlinelibrary.wiley.com\/doi\/10.1111\/mec.70085 ABSTRACT Salmonids have a remarkable ability to form sympatric morphs after postglacial colonisation of freshwater lakes. These morphs often … Continue reading
Salmonids have a remarkable ability to form sympatric morphs after postglacial colonisation of freshwater lakes. These morphs often differ in morphology, feeding and spawning behaviour. Here, we explored the genetic basis of morph differentiation in Arctic charr (n<\/i>\u2009=\u2009283) by first establishing a high-quality reference genome and then using this in whole genome sequencing of distinct morphs present in two Norwegian and two Icelandic lakes. The four lakes represent the spectrum of genetic differentiation between morphs from one lake with no genetic differentiation between morphs, implying phenotypic plasticity, to two lakes with locus-specific genetic differentiation, implying incomplete reproductive isolation, and one lake with strong genome-wide divergence consistent with complete reproductive isolation. As many as 12 putative inversions ranging from 0.45 to 3.25 Mbp in size segregated among the four morphs present in one lake, Thingvallavatn, and these contributed significantly to the genetic differentiation among morphs. None of the putative inversions were found in any of the other lakes, but there were cases of partial haplotype sharing in similar morph contrasts in other lakes. Our findings are consistent with a highly polygenic basis of morph differentiation with population-specific selection on alleles linked to the development of similar morph phenotypes. The results support a model where morph differentiation is first established through phenotypic plasticity, leading to niche expansion and separation. This may be followed by gradual development of reproductive isolation, locus-specific differentiation and eventually complete reproductive isolation and genome-wide divergence.<\/p>\n <\/p>","protected":false},"excerpt":{"rendered":" Now published in Molecular Ecology Whole genome sequencing reveals how plasticity and genetic differentiation underlie sympatric morphs of Arctic charr. https:\/\/onlinelibrary.wiley.com\/doi\/10.1111\/mec.70085 ABSTRACT Salmonids have a remarkable ability to form sympatric morphs after postglacial colonisation of freshwater lakes. These morphs often … Continue reading ![\"\"](\"https:\/\/uni.hi.is\/apalsson\/files\/2025\/08\/mec70085-fig-0004-m-scaled.jpg\")
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