Fine scale patterning of species distributions in a saxicolous lichen community at Jonas Rockslide, Canadian Rocky Mountains

Distinct patterns of species distribution upon individual rockfaces are found n a saxicolous lichen community growing on a rockslide in the Canadian Rockies. A grid system was used for sampling individual rockfaces and the likelihood of finding a species on particular parts of the rockface was analysed. Use of chemicals in the field and collection of apothecia allowed specific identification of individual lichen thalli. Lichens were divisible into three groups: those which are distributed apparently at random over the rockfaces, those which are more likely to occur on upper, outer and southerly portions of the rockfaces and those which are found more often on lower, inner and northerly portions of the rockfaces. The upper rockface surfaces are often snow‐free in winter while the lower rockface group experiences deeper and more persistent snow cover. Simple microclimatic measurements suggest that temperature also differs across the surface of a rockface. It is hypothesised that lichen distributions are at least in part explained by ecophysiological adaptations to their particular microhabitat, while it is recognised that competition may also play a role in community organisation.