Abstract
Within a woody plant species, environmental heterogeneity has the potential to influence the distribution of genetic variation among populations through several evolutionary processes. In some species, a relationship between environmental characteristics and the distribution of genotypes can be detected, showing the importance of natural selection as the main source of differentiation. Nothofagus dombeyi (Mirb.) Oerst. (Nothofagaceae) is an endemic tree species occurring both in Chile and in Argentina temperate forests. Postglacial history has been studied with chloroplast DNA and evolutionary forces shaping genetic variation patterns have been analysed with isozymes but fine-scale genetic diversity studies are needed. The study of demographic and selection histories in Nothofagus dombeyi requires more informative markers such as single nucleotide polymorphisms (SNP). Genotyping-by-Sequencing tools now allow studying thousands of SNP markers at reasonable prices in nonmodel species. We investigated more than 10 K SNP loci for signatures of local adaptation and showed that interrogation of genomic resources can identify shifts in genetic diversity and putative adaptive signals in this nonmodel woody species.
Highlights
In population genetics and conservation the big question is genetic drift instead of natural selection
Our interest is in patterns of adaptation driven by environmental gradients; we focused on outlier patterns indicating divergent selection (Fst significantly higher than neutral expectations)
Modelled area of N. dombeyi presence under present climate conditions is 88,174 km2 and in the future under dispersal constraints is 72,928 km2. It is not qualified with a status of threatened species, we estimated a decrease of almost 20% of its habitat area in a relatively short time, in the northern populations, associated with Mediterraneaninfluenced climate, which is at least worrisome considering we used the most conservative future climate scenario
Summary
In population genetics and conservation the big question is genetic drift instead of natural selection. Both processes determine evolution, but genetic drift operates randomly and depends on effective population size while natural selection proceeds nonrandomly and relies on environmental variables. The evolution towards hereditary adaptations to the current environment is determined by natural selection and has a direction; genetic drift instead is governed solely by chance. The discovery and genotyping of massive genetic markers are enabled by modern genomic tools at very low cost. This makes the study of adaptive genetic loci possible on a wide range of species, which can facilitate the identification of key biodiversity areas. Kirk and Freeland [10] reviewed
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