Saxifraga gemmulosa Boiss. (Saxifragaceae), an Endemic Nickel Bioindicator from Ultramafic Areas of the Southern Iberian Peninsula

The western Betic Mountain Range contains the largest ultramafic rock area in the Iberian Peninsula. The predominant flora of this southern territory (over two hundred taxa) was screened for Ni accumulation. Only two species showed important concentrations of Ni in their tissues, Alyssum serpyllifolium subsp. malacitanum (Brassicaceae), a Ni hyperaccumulator, and Saxifraga gemmulosa (Saxifragaceae). Saxifraga gemmulosa is a rare endemic species restricted to the ultramafic outcrops of Málaga (South Spain), mainly growing in basic or ultrabasic rock crevices, where it appears with other serpentinophytes such as Asplenium adiantum-nigrum subsp. corunnense (Aspleniaceae). Nickel and other representative elements present in Saxifraga gemmulosa and its soils from Sierra Bermeja (Málaga) were studied by inductively coupled plasma-mass spectrometry (ICP-MS). The structures of the plant were micromorphologically analysed by scanning electron microscopy (SEM) coupled to an Energy-Dispersive X-Ray Probe (EDX). The results showed the Ni hyperaccumulating characteristics of S. gemmulosa. As observed in other Ni hyperaccumulator plants, accumulation was mainly detected in leaf epidermis.