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

Abstract

Background: 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. Results: 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. Conclusions: 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.

Comparative Analyses of Phytochemical Variation Within and Between Congeneric Species of Willow Herb, Epilobium hirsutum and E. parviflorum: Contribution of Environmental Factors

“…Although climatic factors have been major drivers of genetic differentiation among populations for various species ( Castilla et al, 2020 ; Gibson and Moyle, 2020 ), bioclimatic variables exhibit less profound effect on the level of chemical variation in our study. However, altitude is found to be a major environmental factor affecting the level of secondary metabolites by explaining 17% of total variation found in E. hirsutum .…”

Local adaptation and spatiotemporal patterns of genetic diversity revealed by repeated sampling of Caenorhabditis elegans across the Hawaiian Islands

“…Evidence of local adaptation does not rule out that IBD contributes to the patterns of Hawaiian diversity because local adaptation and IBD are not mutually exclusive. For example, recent studies of A. thaliana show that IBD and local adaptation each contribute to patterns of genetic differentiation at the regional scale on the Iberian peninsula (Castilla et al, 2020).…”

Water deficit changes the relationships between epidemiological traits of Cauliflower mosaic virus across diverse Arabidopsis thaliana accessions

“…Here, we measured CaMV accumulation, virulence on vegetative growth and transmission rate by the aphid M. persicae in 24 natural Iberic accessions of A. thaliana presenting a large genetic variability and grown under two contrasting watering treatments 43 . To reflect variable plant responses levels to water deficit and, potentially, to virus infection, we selected the 24 natural accessions of A. thaliana from a large variety of climatic regions and altitudes distributed evenly across the Iberian Peninsula 44 . Significant relationships between climate parameters (isothermality, temperature and precipitation patterns and seasonality) and viral traits were detected depending of the watering treatment.…”