Abstract of paper 4:

This study illustrates the application of molecular genetic methods for testing the effect of
landscape structure and disturbance on functional connectivity, using molecular data for a direct quantification of dispersal and for distinguishing between alternative colonization processes. We developed a model to compare the spatial distribution and spatial genetic structure of the epiphytic lichen Lobaria pulmonaria within the perimeter of two reconstructed 19th century disturbances with a nearby area without stand-level disturbance. Population genetic data suggested that after stand-replacing disturbance, each plot was colonized by one or a few genotypes only, which subsequently spread clonally within a local neighborhood. The model aimed at testing the validity of such an interpretation and assessing the relative importance of local dispersal of clonal propagules vs. long-distance dispersal of clonal or recombinant diaspores. A good model fit was reached for the empirical data on host tree distribution, lichen distribution, and tree- and plot-level genotype diversity of the lichen in the undisturbed area. Although model calibration suggested a predominance of local dispersal of clonal propagules, a substantial contribution of immigration of genotypes by long-distance dispersal was needed to reach the observed levels of genotype diversity. The model could not fully explain the high degree of clonality after stand-replacing disturbance, suggesting that the dispersal process itself may not be stationary but depend on conditions related to disturbance.