Role of ploidy in Arabidopsis arenosa colonization of alpine habitats

Polyploidy is an important driver of plant diversification and adaptation to novel environments. As a consequence of genome doubling, polyploids often exhibit greater colonizing ability or occupy a wider ecological niche than diploids. Although elevation has been traditionally considered as a key driver structuring ploidy variation, we do not know if environmental and phenotypic differentiation among ploidy cytotypes varies along an elevational gradient. Wos and colleagues tested for the consequences of genome duplication on genetic diversity, phenotypic variation and habitat preferences on closely related diploid and tetraploid Arabidopsis arenosa populations that coexist along approx. 2300 m of varying elevation.

The team found minor effects of polyploidy on colonization of alpine stands and low genetic differentiation between the two cytotypes, mirroring recent divergence of the polyploids from the local diploid lineage and repeated reticulation events among the cytotypes. This pattern was corroborated by the absence of ecological niche differentiation between the two cytotypes and overall phenotypic similarity at a given elevation.

The case of A. arenosa contrasts with previous studies that frequently showed clear niche differentiation between cytotypes. The authors say their work stresses the importance of considering genetic structure and past demographic processes when interpreting the patterns of ploidy distributions, especially in species that underwent recent polyploidization events.

The authors conclude, “Our results contrast with laboratory studies documenting the effect of experimentally induced ploidy change in the leading plant model genus Arabidopsis… but add to the recently growing body of evidence that ploidy per se may not necessarily have immediate effects on environmental preferences in nature…”