Metal tolerances and cotolerances in the moss Funaria hygrometrica

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Abstract
Tolerance of copper, zinc, nickel, and cadmium was measured in eight populations of the moss Funaria hygrometrica collected from metal-contaminated mine tailings, contaminated soils near metal smelters, urban areas, and an uncontaminated rural site. Protonemal growth in populations collected from the four most copper-contaminated soils was inhibited by only 10–30% on media with 10 μg g−1 copper, whereas populations from other sites were inhibited by over 80%. Population differences in tolerance of zinc, cadmium, and nickel were not clearly related to environmental contamination by these metals. Variation among populations in growth on the metal treatments (except copper) was related to generalized differences in growth rates rather than to metal tolerance per se. Populations differed by up to 400% in the propensity to form stems on control nutrient medium, and stem formation was negatively correlated with protonemal growth, suggesting trade-offs between these two stages of gametophyte development. The two populations that were most sensitive to all the metals formed stems most prolifically under uncontaminated conditions. In comparison with flowering plants, generalized vigor and cross-tolerance between metals may play a more important part in the ability of F. hygrometrica to colonize contaminated soils, and metal-specific tolerant ecotypes may be less important. Key words: metal tolerance, bryophyte evolution, pollution responses, Funaria hygrometrica.