Evolution of Heavy Metal Tolerance in Bryophytes Ii. An Ecological and Experimental Investigation of the “Copper Moss,” Scopelophila Cataractae (Pottiaceae)

About six bryophyte species (including both mosses and liverworts) are generally thought to be restricted to copper‐enriched substrates and are consequently known as “copper mosses.” One of these, Scopelophila cataractae (Pottiaceae), is known from several sites in southern Arizona and occurs at six localities in the eastern United States. Chemical analyses of substrates from the eastern U.S. localities showed that all but one population grew on copper‐enriched soil. The one substrate sample low in copper was very high in iron. Plants from five of the six eastern U.S. localities for S. cataractae were grown experimentally on four soil types ranging from highly to not contaminated, and all grew best on the soil contaminated with copper, lead, and zinc. There was no significant variation in growth between populations on the four soil treatments. This lack of population differentiation is in contrast to flowering plants and may be related to the absence of sexual reproduction in S. cataractae in North America.