Lichens are terrestrially ubiquitous, yet not all lichens are everywhere. In fact, most lichen species are rare. How does this work, what environmental filters are in place to create unique lichen communities in different areas and at different scales? Here I present work from four different studies, investigating the patterns and potential drivers of lichen diversity and community composition at four different scales. I will present on patterns of lichen diversity on different sidewalk squares in an urban environment, across a moisture gradient on an alpine tundra, across individual trees from the base to the canopy, and across a latitudinal gradient in the Americas. I will introduce the lichen species and functional communities found at each of these scales, and explore the macro- and microclimatic, substrate, as well as biotic factors driving these patterns.