Using salmon to understand evolution
Atlantic salmon populations provide us with many ecosystem services, yet spend their life in two habitats vulnerable to human-driven changes: freshwater and the ocean. Some male salmon are able to reach maturation before migrating from freshwater to the ocean – this is known as early male parr maturation (EMPM). While EMPM is known to have genetic bases, it is especially common in southernmost Atlantic salmon populations, suggesting additional environmental component to this reproductive behavioural trait. The GENEARLY (Genetic determination of early male parr maturation in Atlantic salmon natural populations) research initiative investigated salmon growth, sex and early maturation in controlled environments to determine the factors underlying the EMPM phenomenon. The project combined behavioural ecology, quantitative genetics and population genomics approaches. This was used with state-of-the-art sequencing technology to shed new light on the genetic determinism and the genomic architecture of the EMPM phenotype in natural Atlantic salmon populations. Scientists conducted field experiments to identify environmental and genetic factors that are related to early male maturation. During the experiments, they controlled for environmental factors during the rearing of offspring in a semi-natural setting and genetic factor by performing controlled crosses. Researchers found that part of the EMPM trait had a strong genetic component. They then determined genomic regions and genetic markers that could be linked to EMPM. All identified candidate genetic markers were used to develop a single nucleotide polymorphism genotyping array to complement the genotypic data. This allowed a quantitative trait locus analysis to be conducted on the mapping population and a genomic scan on a natural population, which integrated both neutral and functional polymorphisms. The GENEARLY integrative approach has provided a better understanding of the environmental effects on salmon and especially EMPM. Such insights into evolution of reproductive behaviour in Atlantic salmon will lead to improved conservation practices in the face of global change.
Keywords
Atlantic salmon, genetics, early male parr maturation, GENEARLY, phenotype, single nucleotide polymorphism, quantitative trait locus
