Data from: Microclimatic differentiation of gene pools in the Lobaria pulmonaria symbiosis in a primeval forest landscape

Population genetics of the tree-colonizing lichen Lobaria pulmonaria were studied in the largest primeval beech forest of Europe, covering 10 000 ha. During an intensive survey of the area, we collected 1522 thallus fragments originating from 483 trees, which were genotyped with 8 myco- and 14 photobiont-specific microsatellite markers. The symbionts of L. pulmonaria, mycobiont and photobiont were found to consist of two distinct gene pools, which co-exist within small populations of 3–180 ha in a homogeneous beech forest. The small-scale distribution pattern of the symbiotic gene pools was linked to altitude, and show partitioning to lineages associated with either floodplain or mountain forests. Using approximate Bayesian computation, we dated the divergence of the two fungal gene pools of L. pulmonaria as between the Early and Middle Pleistocene. Both fungal gene pools survived the Pleistocene glacial cycles in the Carpathians, though possibly in climatically different refugia. Fungal diversification prior to this cycles and the selection of photobionts with different altitudinal distributions explain the current sympatric habitat partitioning of L. pulmonaria. In addition, the specific associations among the gene pools of both symbionts lead to different frequencies of the gene pools of L. pulmonaria and its photobiont D. reticulata at the landscape level. The distinct gene pools should be recognized as evolutionarily significant units, and deserve specific conservation priorities in the future, i.e. gene pool A, which is an Early to Middle Pleistocene relic.