| Summary: | The genetics and ecology of speciation represent an active field of study in evolutionary biology. Lake Thingvallavatn in Iceland is a perfect model to study speciation, as four morphs of Arctic charr (\textit{Salvelinus alpinus}) live in the lake, in sympatry. The morphs are differentiated in their feeding behaviours and phenotypic traits. The objective of the project was to study the genetic separation of the morphs along the genome and to understand the genetic status of the Piscivorous (PI)-charr. First, statistical methods were applied to genetic data (SNPs markers) to identify loci where natural selection has led to differentiation between the morphs. Genome regions with a density of high FST values - an estimator for the genetic separation of subpopulations - were identified so that further studies can investigate genes in those genes, for instance genes involved in the developmental differences of the morphs. To this end, a detection algorithm was created and then completed with results from the BayeScan software. Secondly, the study focused on the PI morph, genetic status has not been resolved in previous studies. Principal Components Analysis applied to the genetic data suggests a possible hybrid origin for this morph with parents from the Large Benthic and Planktivorous (PL) morphs, or possibly some genetic similarity between the PI and the PL morphs. To analyse this further, the PIs were divided into two groups : one with individuals grouping with the PL, the second one with possible hybrids. The FST distribution was again analysed and a number of SNPs consistent with the hybridisation hypothesis were found. However, admixture modelisation of the population tempered this conclusion. Sequencing of new individuals will allow a stronger test these hypotheses, with similar analyses as were preformed here. These data suggest genetic differentiation can happen on a short evolutionary time scale and that some of the morphs in the lake may not be fully separated.
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