Facultative hyperaccumulation of heavy metals and metalloids.

Highlights: [•] We review research on plants that hyperaccumulate metals but also occur on low-metal soils. [•] Facultative hyperaccumulators are rare but include several well-known research models. [•] Research on facultative hyperaccumulators has focused disproportionately on a few species. [•] Future studies need to focus on plants from other phylogenetic and geographic groups. [•] We propose new hypotheses regarding the evolution of facultative hyperaccumulation. [ABSTRACT FROM AUTHOR]