Although scientific research on metallophytes in the Region is limited, a number of plants have been described in the literature (see review: Ginocchio & Baker 2004). Recent evidence indicates that three As-hyperaccumulating plants (Bidens cynapiifolia (Asteraceae), Paspalum racemosum and P. tuberosum (Poaceae)) and one possible Cu-tolerant plant (Bidens cynapiifolia) grow near a copper mine in the northern Peruvian Andes (Bech et al. 1997); 11 Ni-hyperaccumulating plants in the serpentine flora of the Goias State in Brazil (Brooks et al. 1990, 1992b); 106 Ni- and one Cu-hyperaccumulating plants in serpentine soils of Cuba (Brooks et al. 1990, 1992b). One Se-hyperaccumulating tree ('monkey nut tree', Lecythis ollaria (Lecythidaceae)) has been reported in Venezuela (Aronow & Kerdel-Vegas 1965); three Zn-tolerant plants and some possible Pb- and As-tolerant plants have been found in Ecuador (Bech et al. 2001, 2002); and some Cu-tolerant ecotypes of wide-spread plant species have been discovered in Chile near a copper smelter (Mimulus luteus var. variegatus (Scrophulariaceae)) (Ginocchio et al. 2002), on tailings sands (Mullinum spinosum (Apiaceae)) (Bech et al. 2002) and near copper mines (Nolana divaricata (Solanaceae)) (Ruelle 1995), Cenchrus echinatus (Poaceae) and Erigeron berterianum (Asteraceae) (Bech et al. 2002). Investigations over ultramafic rocks in Argentina and Paraguay (Reeves & Baker 2000) and heavily metal-polluted soils near a copper smelter in central Chile (Ginocchio 1997,1999,2000) have also been performed by local and international scientists but they have not revealed further metal-tolerant plants.
In the last decade, however, increasing research has occurred in the Region in order to identify metallophytes. For example, scientific explorations performed in two different areas of northcentral Chile have recently resulted in an important number of new descriptions of copper-tolerant plants native and endemic to the country. The first study was carried out in a large area of north-central Chile that has a semi-arid Mediterranean climate type (the Coquimbo Region). Due to historic copper/gold mining a large number, 395 (SERNAGEOMIN 1989,1990), of abandoned tailings storage facilities (TSF) are scattered throughout the area. Furthermore, metal-polluted soils and natural mineralised areas are also quite common inside the area. The results showed that 76 abandoned TSFs have been colonised by 106 local plants, 71% being native and endemic to Chile. In laboratory tests, 33 species were found to be copper-tolerant. A second study was performed in the Yerba Loca Natural Sanctuary (YLNS), a well-known high-alpine valley in central Chile, for its historic surface water anomalies. The YLNS (33° S 60° W) is located c. 60 km east of the city of Santiago and west from the south edge of the Rio Blanco-Los Bronces-Yerba Loca Cu-Mo deposit. A large porphyry Cu deposit (>40 km2) with secondary formation of tourmaline and Cu-Zn-Mo sulphides thus exists at high elevations of the basin. Mineral deposits have long influenced surface water quality of streams in the area which broadly differs from dilute waters described for the high Andes in central Chile, particularly in terms of pH, sulphate content and mineral concentrations. For example, the main stream along the YLNS has acidic pH (4.1 5.3) and high sulphate (>150 mg L 1) and metal content waters (3.6 9.1 mg Cu L 1 and 0.2 mg Zn L 1). These marked gradients in surface water chemistry may have an important role in structuring plant communities at the YLNS, particularly in meadows, as acidic and metal-rich waters are highly toxic to most plant species, thus resulting in tertiary heavy-metal vegetation. In harsh water quality environments only a limited suite of species is adapted to survive and reproduce on highalpine meadows at the YLNS. Indeed, Festuca purpurascens (Poaceae), Gaultheria caespitosa (Ericaceae), Calamagrostis chrysostachya (Poaceae) and Empetrum rubrum (Empetraceae) are abundant in habitats with acidic and metal-rich waters, while Carex macloviana (Cyperaceae), Patosia clandestine ( Juncaceae) and Erigeron andicola (Asteraceae) are abundant in habitats with diluted waters. In the YLNS, a total of 30 potential metallophytes have already been identified but further laboratory testing for metal tolerance is under way.
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