GENETIC BIOGEOGRAPHY OF THE RARE COPPER-MOSS, SCOPELOPHILA-CATARACTAE(POTTIACEAE)

Scopelophila cataractae, one of the so-called ''copper mosses'', has a broad geographic distribution that includes North, Central, and South America, Europe, and Asia, but is rare throughout its range. A geneti c analysis of 32 populations from the United States, Europe, and Asia based on 15 putative allozyme loci indicates that levels of genetic di versity vary among geographic regions. Six European populations are fi xed for the same alleles at all 15 loci, consistent with the hypothesi s that S. cataractae is a recent immigrant in that region. The species is more diverse in the U.S., where it appears to be native. Five popu lations collected on copper-enriched soils around shrines and temples in Tokyo are genetically monomorphic, but Asian populations from anoth er Japanese site, India, and Nepal are exceptionally diverse in terms of numbers of alleles and multilocus haplotypes, total gene diversity (H-T), and in the degree of differentiation among populations (measure d as Nei's I and D). Long-distance dispersal has probably played an im portant role in the geographic history of S. cataractae, but the speci es appears to be native in both the New and Old Worlds. Gene flow betw een plants disjunct on different continents is insufficient to explain the lack of geographically correlated morphological and genetic diffe rentiation in S. cataractae.