Nickel hyperaccumulation by Streptanthus polygaloides is associated with herbivory tolerance

Hyperaccumulation of nickel but not selenium drives floral microbiome differentiation: A study with six species of Brassicaceae

PREMISE

Intraspecific variation in flower microbiome composition can mediate pollination and reproduction, and so understanding the community assembly processes driving this variation is critical. Yet the relative importance of trait-based host filtering and dispersal in shaping among-species variation in floral microbiomes remains unknown.

METHODS

Within two clades of Brassicaceae, we compared diversity and composition of floral microbiomes in natural populations of focal nickel and selenium hyperaccumulator species and two of their non-accumulating relatives. We assessed the relative strengths of floral elemental composition, plant phylogenetic distance (host filtering), and geography (dispersal) in driving floral microbiome composition.

RESULTS

Species in the nickel hyperaccumulator clade had strongly divergent floral microbiomes, the most of that variation driven by floral elemental composition, followed by geographic distance between plant populations and, lastly, phylogenetic distance. Conversely, within the selenium hyperaccumulator clade, floral microbiome divergence was much lower among the species and elemental composition, geography, and plant phylogeny were far weaker determinants of microbiome variation.

CONCLUSIONS

Our results show that the strength of elemental hyperaccumulation's effect on floral microbiomes differs substantially among plant clades, possibly due to variation in elements as selective filters or in long-distance dispersal probability in different habitats.

Closely-related species of hyperaccumulating plants and their ability in accumulation of As, Cd, Cu, Mn, Ni, Pb and Zn

Soil contamination by heavy metals is widespread. Heavy metals of concern include As, Cd, Cu, Cr, Mn, Ni, Pb, and Zn. Hyperaccumulating plants are efficient in accumulating metals, which have potential to remediate metal-contaminated soils. Species of closely-related hyperaccumulating plants have been used to screen their ability in metal accumulation. However, there is limited evidence to show that closely-related plant species have similar ability in metal accumulation. Using a global database of 664 hyperaccumulating plants, we constructed a phylogeny of hyperaccumulating plants of As, Cd, Cu, Cr, Mn, Ni, Pb, and Zn. We evaluated the phylogenetic randomness of plants hyperaccumulating different metals by comparing the minimum number of trait-state changes across the phylogenetic tree to a null model. Based on the D value, we evaluated whether closely-related plants tend to accumulate similar metals. Based on the Blomberg's K and Pagel's λ, we tested whether closely-related plants have similar ability in metal accumulation. Excluding Cd and Pb, closely-related plant species tend to accumulate similar metal, however, its ability cannot be predicted based on phylogenetic relations except Ni. Therefore, we concluded that focusing on species of closely-related hyperaccumulating plants can help to screen new hyperaccumulators although their ability could be different.