Edaphic factors as genetic selection agents and adaptation drivers of native plant species in harsh environments of the Brazilian savanna

Background The highly diversified flora in the Brazilian Cerrado (savanna) region is attributed to several factors, including the high concentrations of metals in soils, especially Al in widespread Ferralsols and Ni in soils derived from ultramafic rocks. We hypothesized that adaptation mechanisms are responsible for the genetic diversity of the following native plant species that are found in the abovementioned environments: Euploca salicoides (ES ) , Justicia lanstyakii (JL), and Oxalis hirsutissima (OH). Objectives We aimed to analyse the main edaphic factors that differentiate ultramafic from Al-rich environments, and act as drivers of the evolution of physiological mechanisms underlying plant adaptation to these harsh environments. Methods We analysed the chemical attributes of four ultramafic soils (SAP5, SAP7, SAP9, LAT) and an Al-rich soil (CAM), and the elemental composition and DNA of the three species growing in both environments. ES was used as a model species to analyse changes in the levels of non-structural carbohydrates (NSCs) and Ni localization in plant leaves. Results The soil types presented significant differences in available nutrients and heavy metals. The DNA sampled from the same species from ultramafic sites was genetically closer, but different from that in the Al-rich sites. In ultramafic soils, ES accessions had high levels of NSCs and Ni accumulated in trichomes. Conclusions The genetic diversity observed in plants growing in both areas is probably related to plant adaptation to the contrasting edaphic conditions of these environments. The raffinose production and Ni allocation to trichomes are mechanisms employed by ES to overcome metal toxification in ultramafic environments.