Postglacial ecotype formation under outcrossing and self‐fertilization inArabidopsis lyrata

Abstract

The formation of ecotypes has been invoked as an important driver of postglacial biodiversity, because many species colonized heterogeneous habitats and experienced divergent selection. Ecotype formation has been predominantly studied in outcrossing taxa, while far less attention has been paid to the implications of mating system shifts. Here, we addressed whether substrate‐related ecotypes exist in selfing and outcrossing populations of Arabidopsis lyrata subsp. lyrata and whether the genomic footprint differs between mating systems. The North American subspecies colonized both rocky and sandy habitats during postglacial range expansion and shifted the mating system from predominantly outcrossing to predominantly selfing in a number of regions. We performed an association study on pooled whole‐genome sequence data of 20 selfing or outcrossing populations, which suggested genes involved in adaptation to substrate. Motivated by enriched gene ontology terms, we compared root growth between plants from the two substrates in a common environment and found that plants originating from sand grew roots faster and produced more side roots, independent of mating system. Furthermore, single nucleotide polymorphisms associated with substrate‐related ecotypes were more clustered among selfing populations. Our study provides evidence for substrate‐related ecotypes in A. lyrata and divergence in the genomic footprint between mating systems. The latter is the likely result of selfing populations having experienced divergent selection on larger genomic regions due to higher genome‐wide linkage disequilibrium.

Cold tolerance in the genusArabidopsis

“…Thus, although some measures of cold tolerance may reveal a latitudinal cline in A. lyrata , our results do not. Unlike populations of A. thaliana and A. kamchatica , A. lyrata populations are highly differentiated (Wright et al., ; Mattila et al., ), and they show strong local climate adaptation (Leinonen et al., , , ; Hämälä et al., ; Lucek et al., ). The counter‐adaptive effects of gene flow or recent divergence are not a likely explanation for the lack of a latitudinal cline in A. lyrata .…”

Lineage‐specific adaptation to climate involves flowering time in North American Arabidopsis lyrata

“…We used a similar bioinformatics pipeline as described by Lucek, Hohmann, and Willi (2019). Trimming was performed for each library and lane separately using the Perl script trim‐fastq.pl from the software package PoPoolation (Kofler et al, 2011) with a minimum base quality of 28 and a minimum length of 84 bp.…”