Parallel alpine differentiation inArabidopsis arenosa

Abstract

Parallel evolution provides powerful natural experiments for studying repeatability of evolution. Well-documented examples from plants are, however, still rare, as are inquiries of mechanisms driving convergence in some traits while divergence in others. Arabidopsis arenosa, a predominantly foothill species with scattered morphologically distinct alpine occurrences is a promising candidate. Yet, the hypothesis of parallelism remained untested. We sampled foothill and alpine populations in all regions known to harbour the alpine ecotype and used SNP genotyping to test for repeated alpine colonisation. Then, we combined field surveys and a common garden experiment to quantify phenotypic parallelism. Genetic clustering by region but not elevation and coalescent simulations demonstrated parallel origin of alpine ecotype in four mountain regions. Alpine populations exhibited parallelism in height and floral traits which persisted after two generations in cultivation. In contrast, leaf traits were distinctive only in certain region(s), reflecting a mixture of plasticity and genetically determined non-parallelism. We demonstrate varying degrees and causes of parallelism and nonparallelism across populations and traits within a plant species. Parallel divergence along a sharp elevation gradient makes A. arenosa a promising candidate for studying genomic basis of adaptation.

Genomic basis of parallel adaptation varies with divergence inArabidopsisand its relatives

“…Previous genetic and phenotypic investigations and follow-up analyses presented here showed that the scattered alpine forms of both species represent independent alpine colonization in each mountain range, followed by parallel phenotypic differentiation (Fig. 1d, e) (43, 44). Thus, we sequenced genomes from seven alpine and adjacent foothill population pairs, covering all European lineages encompassing the alpine ecotype.…”

“…Second, as genetic divergence often corresponds to the spatial arrangement of lineages 55 , external challenges posed by the alpine environment at remote locations may differ. Such risk is, however, mitigated at least in our Arabidopsis dataset, as the genomically investigated alpine populations share very similar niches 42 In contrast, no relationship between the probability of gene reuse and divergence was shown in experimental evolution of different populations of yeast 56 raising a question about the generality of our findings. Our study addresses a complex selective agent (a multihazard alpine environment 57 ) in order to provide insights into an ecologically realistic scenario relevant for adaptation in natural environments 14,53,54 ..…”

“…(e) Morphological differentiation among 223 A. arenosa individuals originating from foothill (black) and alpine (gray) populations from four regions after two generations in a common garden. Principal component analysis was run using 16 morphological traits taken from (44).…”

Phenotypic and genotypic parallel evolution in parapatric ecotypes ofSenecio

“…To characterize the extent of phenotypic and genotypic parallelism within a system, it is necessary to rigorously demonstrate that populations adapting to similar environments (collectively referred to as an ecotype) have arisen multiple times independently. We refer the reader to our previous analyses of parallel evolution in Senecio lautus (Roda et al, 2013b;James et al, 2020) and to systems such as the marine snail, Littorina saxatilis (Quesada et al, 2007;Johannesson et al, 2010;Bierne et al, 2013;Butlin et al, 2014;Pérez-Pereira et al, 2017), and the threespine stickleback, Gasterosteus aculeatus (Colosimo et al, 2005;Chan et al, 2010;Dean et al, 2019;Marques et al, 2019) where one can find some of the strongest evidence for the independent origin of populations, and to the increasing number of potential cases of parallel evolution in plants (Foster et al, 2007;Ostevik et al, 2012;Trucchi et al, 2017;Cai et al, 2019;Konečná et al, 2019;Knotek et al, 2020).…”

Parallel Alpine Differentiation in Arabidopsis arenosa

“…Computational resources were provided by the CESNET LM2015042 and the CERIT Scientific Cloud LM2015085. This manuscript has been released as a pre-print at BioRxiv, https://doi.org/10.1101/2020.02.13.948158 ( Knotek et al, 2020 ).…”