Assessment of plant diversity and foliar chemistry on the Sri Lankan ultramafics reveals inconsistencies in the metal hyperaccumulator trait

Some of the largest expanses of ultramafic soils occur in South Asia, but knowledge of the plant diversity and biogeochemistry of these systems in Sri Lanka is very limited. This study aimed to assess the plant diversity and bedrock and foliar chemistry of all known Sri Lankan ultramafic outcrops. The field survey yielded a total of 132 plant taxa from 44 families. The enigmatic nickel hyperaccumulator Rinorea bengalensis (Violaceae), first reported in Sri Lanka over four decades ago, was rediscovered at a newly surveyed ultramafic site, however, it did not hyperaccumulate nickel. No new metal hyperaccumulator plants were identified, suggesting that R. bengalensis is a facultative nickel hyperaccumulator. This study is the first to highlight the floristic diversity of all known Sri Lankan ultramafic outcrops while revealing the facultative nature of nickel and copper hyperaccumulation among some of Sri Lanka's ultramafic plants.