Microclimatic differentiation of gene pools in theLobaria pulmonariasymbiosis in a primeval forest landscape

Abstract

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 eight mycobiont- and 14 photobiont-specific microsatellite markers. The mycobiont and photobiont of L. pulmonaria were found to consist of two distinct gene pools, which are co-existing within small areas of 3-180 ha in a homogeneous beech forest. The small-scale distribution pattern of the symbiotic gene pools show habitat partitioning of lineages associated with either floodplains or mountain forests. Using approximate Bayesian computation (ABC), we dated the divergence of the two fungal gene pools of L. pulmonaria as the Early Pleistocene. Both fungal gene pools survived the Pleistocene glacial cycles in the Carpathians, although possibly in climatically different refugia. Fungal diversification prior to these cycles and the selection of photobionts with different altitudinal distributions explain the current sympatric, but ecologically differentiated habitat partitioning of L. pulmonaria. In addition, the habitat preferences of the mycobiont are determined by other factors and are rather independent of those of the photobiont at the landscape level. The distinct gene pools should be considered evolutionarily significant units and deserve specific conservation priorities in the future, for example gene pool A, which is a Pliocene relict.

Fungal specificity and selectivity for algae play a major role in determining lichen partnerships across diverse ecogeographic regions in the lichen‐forming family Parmeliaceae (Ascomycota)

“…; Nadyeina et al . ), and ecoregion delimitations fail to capture this level of ecological variation. Additional detailed examinations of the distribution of lichen photobionts across microhabitat scales will likely provide a more nuanced perspective into patterns driving interactions in lichen symbioses (e.g.…”

Discovery of long‐distance gamete dispersal in a lichen‐forming ascomycete

“…), which should lead to high genetic variability (Williams, ). High variability and a high proportion of colonizations originating from (recombined) ascospores were indeed found in the old‐growth forest, similar to reports in other studies (Werth et al ., ; Hilmo et al ., ; Nadyeina et al ., ). On the contrary, in heavily managed forests, local population densities are often low, distances amongst host trees are large (Gu et al ., ) and short‐distance dispersal dominates (Belinchón et al ., ).…”

High-Throughput Sequencing in Studies of Lichen Population Biology

“…On a larger spatial scale (several km 2 ), multiple, intermingled fungal and algal gene pools have been observed (Nadyeina et al 2014b;Werth and Scheidegger 2012) and gene pool associations with elevation have been interpreted as evidence of climate-driven local adaptations in the mycobionts . On a landscape scale, climatic associations of fungal and algal gene pools have also been found for L. pulmonaria in the largest continuous primeval forest of Europe (Nadyeina et al 2014b).…”

“…On a landscape scale, climatic associations of fungal and algal gene pools have also been found for L. pulmonaria in the largest continuous primeval forest of Europe (Nadyeina et al 2014b). At the largest spatial scale, genetic differentiation of populations of L. pulmonaria mycobionts and photobionts has been shown within Europe and between continents Walser et al 2005;Widmer et al 2012).…”

“…This represents one of the great challenges to population genetic research. Green algal photobionts show preferences for specific ecological conditions such as phorophyte species, habitats, and altitudinal zones (Nadyeina et al 2014b;Peksa and Škaloud 2011;Sork 2010, 2014;Yahr et al 2006). As elevation is closely correlated with several macroclimatic parameters (temperature, precipitation and wind), altitudinal distributions of genotypes likely result from local adaptation of the symbionts' genotypes to specific local climatic conditions.…”