Genetic variation and ecotypic differentiation in the haploid moss, Ceratodon purpureus (Hedw.) Brid.

Abstract

Inferences made from biogeographic patterns and geological history have led to the view of bryophytes as having little genetic variation within or among populations. We conducted a sterile agar experiment to test for genetic variation for metal-tolerance among populations of the common moss, Ceratodon purpureus (Hedw.) Brid., as measured by differences in the protonemal growth of individuals on varying degrees of metal-enrichment. Also, we conducted a common garden experiment to test for genetic variation among populations as measured by differences in plant cover area, stem count, and gametangial formation produced by the regeneration of gametophytic fragments on soils of varying metal-concentrations. Results from the agar experiment indicate that plants from one population growing near a zinc smelter erected in 1898 were significantly more tolerant of zinc, cadmium, and lead. Results from the garden experiment indicate that plants from a second poulation near the same smelter are significantly more tolerant of contaminated soils for all performance traits measured. Metal-tolerant plants grew fewer stems and produced fewer gametangia on the control treatment than on the metal-contaminated treatment in the garden experiment; there is a biological cost for tolerance in C. purpureus. Genetic variation for metal-tolerance exists among populations of C. purpureus. Furthermore, significant evolutionary adaptation can occur rapidly in C. purpureus when directional selection is intense.