Ecological, genetic and evolutionary drivers of regional genetic differentiation in Arabidopsis thaliana

• Published in: BMC ecology and evolution 2020-06, Vol.20 (1), p.71-71, Article 71
• Main Authors: Castilla, Antonio R, Méndez-Vigo, Belén, Marcer, Arnald, Martínez-Minaya, Joaquín, Conesa, David, Picó, F Xavier, Alonso-Blanco, Carlos
• Format: Article
• Language: English
• Subjects: Altitude; Analysis; Animal behavior; Arabidopsis - genetics; Arabidopsis thaliana; Bayesian analysis; Biodiversity; Changing environments; Differentiation; Dispersal; Dispersion; Environment; Environmental gradient; Evolution; Evolution, Molecular; Genetic analysis; Genetic diversity; Genetic Drift; Genetic research; Genetic structure; Genetic Variation; Genome, Plant - genetics; Genomes; Genomics; Genotype; Geographical distribution; Habitats; Heterogeneity; Iberian Peninsula; Mathematical models; Motor vehicle drivers; Nested maximum-likelihood population effect models; Population; Population distribution; Population genetics; Precipitation; Precipitation seasonality; Seasonal variations; Single-nucleotide polymorphism; Spatial hierarchical Bayesian models; Topsoil
• ISSN: 1471-2148; 1471-2148; 2730-7182
• DOI: 10.1186/s12862-020-01635-2

Disentangling the drivers of genetic differentiation is one of the cornerstones in evolution. This is because genetic diversity, and the way in which it is partitioned within and among populations across space, is an important asset for the ability of populations to adapt and persist in changing environments. We tested three major hypotheses accounting for genetic differentiation-isolation-by-distance (IBD), isolation-by-environment (IBE) and isolation-by-resistance (IBR)-in the annual plant Arabidopsis thaliana across the Iberian Peninsula, the region with the largest genomic diversity. To that end, we sampled, genotyped with genome-wide SNPs, and analyzed 1772 individuals from 278 populations distributed across the Iberian Peninsula. IBD, and to a lesser extent IBE, were the most important drivers of genetic differentiation in A. thaliana. In other words, dispersal limitation, genetic drift, and to a lesser extent local adaptation to environmental gradients, accounted for the within- and among-population distribution of genetic diversity. Analyses applied to the four Iberian genetic clusters, which represent the joint outcome of the long demographic and adaptive history of the species in the region, showed similar results except for one cluster, in which IBR (a function of landscape heterogeneity) was the most important driver of genetic differentiation. Using spatial hierarchical Bayesian models, we found that precipitation seasonality and topsoil pH chiefly accounted for the geographic distribution of genetic diversity in Iberian A. thaliana. Overall, the interplay between the influence of precipitation seasonality on genetic diversity and the effect of restricted dispersal and genetic drift on genetic differentiation emerges as the major forces underlying the evolutionary trajectory of Iberian A. thaliana.