Comparing element composition of rock substratum with lichen communities and the fecundity of Arctoparmelia and Xanthoparmelia species.

Substratum plays an important role in saxicolous lichen communities, providing a stable growth surface for long-term attachment and influencing the relative abundance of species. Saxicolous lichen communities consisting of Xanthoparmelia and Arctoparmelia were previously characterized using thallus cover on the substratum as well as lichen fecundity, but it was not known whether the substratum influenced lichen fecundity. The objectives of this paper were to compare variation in element concentrations among lichen communities, and to examine the correlation between elemental composition and percent cover and fecundity (numbers of apothecia, ascospores, and percent germination) of each of three lichens Arctoparmelia centrifuga, Xanthoparmelia viriduloumbrina, and X. cumberlandia. Percent cover and fecundity features were compared with the rock type and 21 elements from 37 transects. Element concentrations varied among communities, but the grassy rock community had significantly higher concentrations of elements than the mossy or treed rock communities. Positive correlations were present between fecundity and particular elements for the three species. This study provides insight into the complexity of the relationship between the geological composition of the substratum and saxicolous lichen biology. [ABSTRACT FROM AUTHOR]