Environmental factors in saxicolous lichen communities are scale dependent, yet the influence of scale is not often specifically addressed in ecological studies. This study examined three scales [micro (cm), meso (meters–10s of meters), macro (km)] in granite rock communities and compared species assemblages and disturbance regimes in Lake Superior shoreline and inland habitats. Percent cover of lichens and environmental variables were measured in 1280 20 × 20-cm plots across 16 sites (8 lakeshore and 8 inland). A perMANOVA analysis showed that the composition of lakeshore and inland lichen communities was significantly different (F=17.2, df=1,4, P <0.001). Adjacent lakeshore sites were more similar (F=8.550; df = 1, 26; p=0.007) to each other than they were to sites further away, while inland sites were not (F=0.545; df=1, 26; p=0.467). Variation in disturbance is likely more important in determining inter-site variation in inland areas. Mesoscale environmental variables such as solar radiation, height above Lake Superior, and an aspect/slope index were better predictors of species assemblages than microscale variables. However, individual species differed greatly in their associations with specific habitat variables. A host of microhabitats were discovered, with some lichens specializing on rock overhangs, quartz veins, cracks, subtle variations in rock texture, and mafic intrusions within granite.
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Vol. 125 • No. 1