Revisiting endophytic fungi of the Pinus-Viscum-system to assess interdependencies among factors driving community structure.

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Nearly all plants studied so far are inhabited by a complex assemblage of endophytic fungi. However, the factors driving the composition of these communities are poorly understood. In a previous project we obtained first evidence that the endophytic fungi in leaves and stems differ with regard to diversity, variability, and host-selectivity. Several hypotheses resulted from that study. These hypotheses to be tested in the proposed project are that (a) the stem-inhabiting fungal community is rather poor in species, (b) to a certain degree selective for their host plant species, and (c) does not change through time in adult host plants. In contrast, (d) the diversity within leaves is assumed to increase with increasing leaf age and (e) the spectrum of accumulating fungi is not host-selective. Its composition rather depends on the availability of suitable substrates for fungal sporulation (i.e. decaying plant material) in the surrounding environment and therefore on the composition of the plant community. To verify these hypotheses the previously studied Pinus-Viscum-system is chosen because i) the age of the organs of both plants is easily determinable, ii) both species comprise at least current- and previous-year leaves, and iii) they are exposed to the same spectrum of fungal spores, due to their close proximity. Pyrosequencing will be applied to fungal DNA in each of five replicates of differently aged stems and leaves of each species of the Pinus-Viscum-system and non-infected Pinus trees in addition. The extensive data gathered this way will allow addressing the hypotheses on a statistically sound background. The applicability of the proposed methodology has previously been verified and success of the pyrosequencing run is guaranteed by an external contractor.