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 genetic analysis of 32 populations from the United States, Europe, and Asia based on 15 putative allozyme loci indicates that levels of genetic diversity vary among geographic regions. Six European populations are fixed for the same alleles at all 15 loci, consistent with the hypothesis 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 populations collected on copper-enriched soils around shrines and temples in Tokyo are genetically monomorphic, but Asian populations from another 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 (measured as Nei's I and D). Long-distance dispersal has probably played an important role in the geographic history of S. cataractae, but the species appears to be native in both the New and Old Worlds. Gene flow between plants disjunct on different continents is insufficient to explain the lack of geographically correlated morphological and genetic differentiation in S. cataractae.