Abstrakt
Background and aims - Subaerial phototrophic biofilms growing on tree bark represent one of the least-known micro-algal communities. Ecological distribution patterns of major micro-algal groups thriving in corticolous microhabitats on eleven host tree species in sub-Mediterranean and temperate European localities were investigated in the present study.
Methods - In total, 169 samples of corticolous biofilms were investigated by direct light microscopy. Microalgae were identified to the lowest putatively monophyletic groups that could be distinguished unambiguously.
Among other abiotic factors, the pH of the bark surface was measured using a flathead electrode, and the proportion of open sky at individual sites was evaluated by image analysis of fisheye circular photographs. Key results - The distribution of the putatively trebouxiophycean coccoid green algae was mostly related to microscale factors, such as sample orientation on trunks.
Conversely, the distribution of Trentepohliales and Cyanobacteria was related mostly to bark pH values and to regional differences between temperate and sub-Mediterranean localities. The distribution of some streptophytan taxa, such as Mesotaenium or Spirotaenia, was closely related to particular host tree species.
Conclusions - Individual major groups of corticolous algae and Cyanobacteria in European ecosystems have distinctly different ecological strategies in relation to important abiotic factors.