Metal accumulation by Alyssum serpyllifolium subsp. malacitanum Rivas Goday (Brassicaceae) across different petrographic entities in South-Iberian ultramafic massifs: plant-soil relationships and prospects for phytomining

Abstract

In the ultramafic area of Spain, a high quantity of petrographic entities is present. Data on the variability between populations of hyperaccumulation are scarce. We investigated Alyssum serpyllifolium subsp. malacitanum for variation in eleven elements between populations growing in different ultramafic massifs across different petrographic entities (dunites, harzburgite-pyroxenic dunite, harzburgite-lherzolite, pyroxenite and serpentinites).Samples of leaves and soils were collected from the ultramafic outcrops of Sierra Bermeja and Sierra de Mijas (Andalusia, Spain). Concentrations of Ni, Fe, Mg, Si, Cr, Co, Sr, Mn, Cu, Zn and Ba and the Bioaccumulation factors (BAF) were determined.Although analysis of variance of data for each element revealed considerable variation in the soil chemistry (for Fe, Mg, Sr and Ba) across different petrographic entities, population-level variation with regard to the hyperaccumulation in the leaves was not detected. BAF values greater than one were obtained for Sr and Ni depending on the petrographic entities. The correlation detected between the concentration of Ni in the leaves and its concentration in the soil is relevant.The population-level variation obtained in the BAF for Sr and Ni provide comprehensive information on the natural variation of hyperaccumulation. The BAF obtained for Ba is an important result for phytomining.

An updated checklist of serpentinophytes for research and conservation in ultramafic ecosystems on the southern Iberian Peninsula (Spain)

“…To date, studies on serpentine flora and its distribution across the different ultramafic rocks have been conducted on an individual serpentinophyte (i.e., Alyssum serpyllifolium subsp. malacitanum, Manteca-Bautista et al, 2022) but not for the whole group of such plants.…”

“…We repeated that procedure without considering the category of serpentinophyte affinity in order to evaluate whether the occupancy of each serpentinophyte species varied by petrographic entity. We also elaborated heatmaps for each serpentinophyte using the petrographic entities of the province of M alaga elaborated by Manteca-Bautista et al (2022).…”

“…Together with the presence of heavy metals in the composition of peridotites, the abundance of Mg, and very low amounts of Ca (Morais et al, 2015), another conditioning factor is the mineralogical and lithological difference in the composition of ultramafic rocks. That fact may determine different concentrations of those elements in the soil (Morais et al, 2015) and therefore affect the assembly of plants (Manteca-Bautista et al, 2022) in different ways and can vary the petrological affinity of serpentinophytes. The presence of each heavy metal and variability in the Mg/Ca ratio occurring in southern Iberian ultramafic outcrops contribute to diverse rock types such as dunite, harzburgite-pyroxenite-dunite, harzburgite-lherzolite, pyroxenite, and serpentinite (Manteca-Bautista et al, 2022).…”

“…That fact may determine different concentrations of those elements in the soil (Morais et al, 2015) and therefore affect the assembly of plants (Manteca-Bautista et al, 2022) in different ways and can vary the petrological affinity of serpentinophytes. The presence of each heavy metal and variability in the Mg/Ca ratio occurring in southern Iberian ultramafic outcrops contribute to diverse rock types such as dunite, harzburgite-pyroxenite-dunite, harzburgite-lherzolite, pyroxenite, and serpentinite (Manteca-Bautista et al, 2022). Our study also attempted to determine whether the distribution of serpentinophytes is associated with certain specific types of ultramafic rocks.…”

“…Southern Iberian serpentine flora also grows in different ultramafic massifs that contain different petrographic entities (IGME, 1978; Manteca‐Bautista et al, 2022). Together with the presence of heavy metals in the composition of peridotites, the abundance of Mg, and very low amounts of Ca (Morais et al, 2015), another conditioning factor is the mineralogical and lithological difference in the composition of ultramafic rocks.…”