title: Genomic and phenotypic differentiation of Arabidopsis thaliana along altitudinal gradients in the North Italian Alps.
abstract: Altitudinal gradients in mountain regions are short-range clines of different environmental parameters such as temperature or radiation. We investigated genomic and phenotypic signatures of adaptation to such gradients in five Arabidopsis thaliana populations from the North Italian Alps that originated from 580 to 2350 m altitude by resequencing pools of 19-29 individuals from each population. The sample includes two pairs of low- and high-altitude populations from two different valleys. High-altitude populations showed a lower nucleotide diversity and negative Tajima's D values and were more closely related to each other than to low-altitude populations from the same valley. Despite their close geographic proximity, demographic analysis revealed that low- and high-altitude populations split between 260 000 and 15 000 years before present. Single nucleotide polymorphisms whose allele frequencies were highly differentiated between low- and high-altitude populations identified genomic regions of up to 50 kb length where patterns of genetic diversity are consistent with signatures of local selective sweeps. These regions harbour multiple genes involved in stress response. Variation among populations in two putative adaptive phenotypic traits, frost tolerance and response to light/UV stress was not correlated with altitude. Taken together, the spatial distribution of genetic diversity reflects a potentially adaptive differentiation between low- and high-altitude populations, whereas the phenotypic differentiation in the two traits investigated does not. It may resemble an interaction between adaptation to the local microhabitat and demographic history influenced by historical glaciation cycles, recent seed dispersal and genetic drift in local populations.
authors.affiliation: Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, Stuttgart, Germany.|Department of Evolutionary Biology, EBC, Uppsala University, Uppsala, Sweden.
authors.forename: Torsten
authors.initials: T
authors.lastname: Günther
authors.affiliation: Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, Stuttgart, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Lampei
authors.affiliation: Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, Stuttgart, Germany.
authors.forename: Ivan
authors.initials: I
authors.lastname: Barilar
authors.affiliation: Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, Stuttgart, Germany.
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Schmid
mesh_terms: D000531:Altitude; D017360:Arabidopsis / Q000235:genetics*; D005787:Gene Frequency; D040961:Genetic Drift; D014644:Genetic Variation; D005828:Genetics, Population; D018745:Genome, Plant; D023281:Genomics; D007558:Italy; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide
keywords: adaptation; evolution; landscape genetics; natural selection and contemporary; population genetics - empirical