Experimental and field data support habitat expansion of the allopolyploid Arabidopsis kamchatica owing to parental legacy of heavy metal hyperaccumulation

Little empirical evidence is available whether allopolyploid species combine or merge adaptations of parental species. The allopolyploid species Arabidopsis kamchatica is a natural hybrid of the diploid parents A. halleri, a heavy metal hyperaccumulator, and A. lyrata, a non-hyperaccumulating species. Zinc and cadmium were measured in native soils and leaf tissues in natural populations, and in hydroponic cultures of A. kamchatica and A. halleri. Pyrosequencing was used to estimate homeolog expression ratios. Soils from human modified sites showed significantly higher Zn concentrations than non-modified sites. Leaf samples of A. kamchatica collected from 40 field localities had > 1,000 {micro}g g-1 Zn in over half of the populations, with significantly higher amounts of Zn concentrations in plants from human modified sites. In addition, serpentine soils were found in two populations. Most genotypes accumulated >3000 {micro}g g-1 of Zn in hydroponic culture with high variability among them. Genes involved in hyperaccumulation showed a bias in the halleri-derived homeolog. A. kamchatica has retained constitutive hyperaccumulation ability inherited from A. halleri. Our field and experimental data provides a compelling example in which the inheritance of genetic toolkits for soil adaptations likely contributed to the habitat expansion of an allopolyploid species.