Performance of macrolichens and lichen genera as indicators of lichen species richness and composition

In the search for cost-effective methods for measuring and monitoring lichen diversity, we tested the performance of two possible indicators: lichen genus diversity and macrolichen diversity. We studied the lichen vegetation of eight European countries situated in six different biogeographic regions. In each country, six land-use units (each 1 km(2)) representing a land-use gradient ranging from old-growth forest to farmland were sampled (n=48) for terricolous, saxicolous, and epiphytic lichens at 16 plots each. We found 768 different lichen species belonging to 157 genera. Relationships between richness and density of genera and species, species and macrolichens, and crustose lichens and macrolichens were highly significant (p<0.001) for all substrates combined and for epiphytic and saxicolous lichens. Richness and density of genera and macrolichens explained a large amount. of variation of the species richness and density (R(2): 71.9%-98.0%). The relationship between crustose lichens and macrolichens explained less of the variation (R(2): 37.7%-70.1%). Effects of land-use intensity on the richness and density of genera, species, and crustose lichens were similar, except for a strong difference between the forested and the more open land-use units for epiphytic crustose lichens. For epiphytic macrolichens there were fewer significant effects. Detrended correspondence analysis indicated similar ordering of sites along the major gradients and similar length of these gradients for genera, species, macrolichens, and crustose lichens. Both genera and macrolichens are useful indicators of total lichen species richness and density. Macrolichens, however, are more suitable indicators than genera owing to (1) their more stable taxonomy of species than of genera, (2) the potential that nonspecialists could do the sampling, (3) the limited use of genera data for species conservation, and (4) the fact that species extinctions will not be indicated by nonmonotypic genera.