The most important modes of adaptive differentiation across a species climatic range are often associated with shifts in life history traits. Understanding how selective pressures act on life history traits and the effect of this selection on population dynamics can be crucial for managing populations and the genetic diversity they contain. However few empirical studies have merged population dynamics, selection on life history, and their evolutionary consequences. In the research presented we approach the question: Are certain life strategies within a species selected in different climatic environments? If so, does this lead to genetic differentiation among populations? To explore these questions demographic surveys and molecular genetic analysis have been combined. Eight populations of Arabidopsis thaliana have been selected along an altitudinal gradient representative of the environmental range of distribution of the species in the Iberian Peninsula. Demographic surveys above and below ground and molecular genotyping of 15 individuals with 144 SNP´s have been performed in each population.
Results/Conclusions
Winter seedling mortality and seed dormancy in the soil increases gradually with altitude. Meanwhile, gene diversity decreases with altitude, with the populations with greater winter mortality and dormancy being less genetically diverse. These results suggest: 1) In environments where winter mortality is high, high dormancy appears to be favored by selection. 2) As this pattern is gradual across altitude, it can be due to processes of local adaptation, or gene flow between differentiated high- and low-altitude regions. 3) A reduction of gene diversity in populations with high winter mortality and more dormancy could be due to higher selection pressures in those environments. Because of high selfing and homozygosity, strong selection on any locus will reduce neutral genetic diversity throughout the genome as well. In highly selfing species, strong selection at the edges of the range or in changing environments may therefore have major consequences for the maintenance of genetic diversity overall.
