ADAPTATION TO METALS IN WIDESPREAD AND ENDEMIC PLANTS

Bryophytes, including the mosses, liverworts, and hornworts, occur in a variety of habitats with high concentrations of metals and have othe r characteristics that are advantageous for studies of metal tolerance . Mosses may evolve genetically specialized, metal-tolerant races less frequently than flowering plants. Some species of mosses appear to ha ve inherently high levels of metal tolerance even in individuals that have not been subjected to natural selection in contaminated environme nts. Scopelophila cataractae, one of the so-called copper mosses, not only tolerates extremely high concentrations of metals in its substrat es, but requires these substrates for optimum growth. This species sho uld be included in mechanistic studies of tolerance at the cellular an d molecular levels.