GENETIC BIOGEOGRAPHY OF THE RARE COPPER MOSS, MIELICHHOFERIA-ELONGATA(BRYACEAE)

Mielichhoferia elongata, one of the so-called ''copper mosses,'' has a broad but highly disjunctive geographic distribution and is rare thro ughout its range. A genetic analysis of 30 populations based on a surv ey of 21 allozyme loci reveals the following. 1) Total gene diversity at the specific level is high (0.41). 2) Within-population diversity i s low, and over 90% of all genetic variation is among rather than with in populations (mean G(ST) = 0.93). 3) There is little differentiation in allele frequencies between North American and European populations . 4) Populations consist of one to six multilocus genotypes; 13 of the populations appear to consist of a single clone. 5) Colorado populati ons contain a tremendous reservoir of genetic variation (88% of all al leles found in the species in North America and Europe occur in one or more Colorado populations). 6) Populations in the eastern and western United States, and in Europe, contain subsets of the allelic diversit y found in Colorado. The genetic structure of M. elongata suggests rep eated dispersal and founding of populations.