title: Validation of outlier loci through replication in independent data sets: a test on Arabis alpina.
abstract: Outlier detection and environmental association analysis are common methods to search for loci or genomic regions exhibiting signals of adaptation to environmental factors. However, a validation of outlier loci and corresponding allele distribution models through functional molecular biology or transplant/common garden experiments is rarely carried out. Here, we employ another method for validation, namely testing outlier loci in specifically designed, independent data sets. Previously, an outlier locus associated with three different habitat types had been detected in Arabis alpina. For the independent validation data set, we sampled 30 populations occurring in these three habitat types across five biogeographic regions of the Swiss Alps. The allele distribution model found in the original study could not be validated in the independent test data set: The outlier locus was no longer indicative of habitat-mediated selection. We propose several potential causes of this failure of validation, of which unaccounted genetic structure and technical issues in the original data set used to detect the outlier locus were most probable. Thus, our study shows that validating outlier loci and allele distribution models in independent data sets is a helpful tool in ecological genomics which, in the case of positive validation, adds confidence to outlier loci and their association with environmental factors or, in the case of failure of validation, helps to explain inconsistencies.
authors.affiliation: WSL Swiss Federal Research Institute Zürcherstrasse 111, CH-8903, Birmensdorf, Switzerland ; Department of Environmental Systems Science, ETH Zürich Universitätsstrasse 16, CH-8092, Zürich, Switzerland.
authors.forename: Dominique
authors.initials: D
authors.lastname: Buehler
authors.affiliation: WSL Swiss Federal Research Institute Zürcherstrasse 111, CH-8903, Birmensdorf, Switzerland ; Department of Environmental Systems Science, ETH Zürich Universitätsstrasse 16, CH-8092, Zürich, Switzerland.
authors.forename: Rolf
authors.initials: R
authors.lastname: Holderegger
authors.affiliation: WSL Swiss Federal Research Institute Zürcherstrasse 111, CH-8903, Birmensdorf, Switzerland.
authors.forename: Sabine
authors.initials: S
authors.lastname: Brodbeck
authors.affiliation: WSL Swiss Federal Research Institute Zürcherstrasse 111, CH-8903, Birmensdorf, Switzerland.
authors.forename: Elvira
authors.initials: E
authors.lastname: Schnyder
authors.affiliation: WSL Swiss Federal Research Institute Zürcherstrasse 111, CH-8903, Birmensdorf, Switzerland.
authors.forename: Felix
authors.initials: F
authors.lastname: Gugerli
keywords: Allele distribution model; SNaPshot®; environmental association analysis; genome scan; natural selection