Microbial Communities Associated with Tree Bark Foliose Lichens: A Perspective on their Microecology

Tree‐bark, foliose lichens occur widely on a global scale. In some locales, such as forests, they contribute a substantial amount of biomass. However, there are few research reports on microbial communities including eukaryotic microbes associated with foliose lichens. Lichens collected from tree bark at 11 locations (Florida, New York State, Germany, Australia, and the Arctic) were examined to determine the density and C‐biomass of bacteria and some eukaryotic microbes, i.e. heterotrophic nanoflagellates (HNF) and amoeboid protists. A rich microbial diversity was found, including large plasmodial slime molds, in some cases exceeding 100 μm in size. The densities of HNF and amoeboid protists were each positively correlated with densities of bacteria, r = 0.84 and 0.80, respectively (p < 0.01, N = 11 for each analysis) indicating a likely bacterial‐based food web. Microbial densities (number/g lichen dry weight) varied markedly across the geographic sampling sites: bacteria (0.7–13.1 × 10⁸), HNF (0.2–6.8 × 10⁶) and amoeboid protists (0.4–4.6 × 10³). The ranges in C‐biomass (μg/g lichen dry weight) across the 11 sites were: bacteria (8.8–158.5), HNF (0.03–0.85), and amoeboid protists (0.08–540), the latter broad range was due particularly to absence or presence of large slime mold plasmodia.