Optimal sample sizes and allelic diversity in studies of the genetic variability of mycobiont and photobiont populations

Werth, Silke

doi:10.1017/s0024282910000563

Cited by 9 publications

(13 citation statements)

References 36 publications

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“…Although the pattern of spatial autocorrelation in genotype diversity was similar in the symbionts, one emerging difference was that gene diversity was slightly higher in the algal than in the fungal data, consistent with the results of rarefaction analyses of a subset of fungal and algal microsatellite markers (Werth 2010a). Moreover, our result of higher diversity in the photobiont is in agreement with the pattern found in other lichen symbioses (Blaha et al 2006;Muggia et al 2008;Ohmura et al 2006;Opanowicz and Grube 2004;Werth and Sork 2010).…”

Section: Discussionsupporting

confidence: 89%

Congruent Genetic Structure in the Lichen-Forming Fungus Lobaria pulmonaria and Its Green-Algal Photobiont

Werth¹,

Scheidegger²

2012

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The extent of codispersal of symbionts is one of the key factors shaping genetic structures of symbiotic organisms. Concordant patterns of genetic structure are expected in vertically transmitted symbioses, whereas horizontal transmission generally uncouples genetic structures unless the partners are coadapted. Here, we compared the genetic structures of mutualists, the lichen-forming fungus Lobaria pulmonaria and its primary green-algal photobiont, Dictyochloropsis reticulata. We performed analysis of molecular variance and variogram analysis to compare genetic structures between symbiosis partners. We simulated the expected number of multilocus-genotype recurrences to reveal whether the distribution of multilocus genotypes of either species was concordant with panmixia. Simulations and tests of linkage disequilibrium provided compelling evidence for the codispersal of mutualists. To test whether genotype associations between symbionts were consistent with randomness, as expected under horizontal transmission, we simulated the recurrence of fungal-algal multilocus genotype associations expected by chance. Our data showed nonrandom associations of fungal and algal genotypes. Either vertical transmission or horizontal transmission coupled with coadaptation between symbiont genotypes may have created these nonrandom associations. This study is among the first to show codispersal and highly congruent genetic structures in the partners of a lichen mutualism.

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Section: Discussionsupporting

confidence: 89%

Congruent Genetic Structure in the Lichen-Forming Fungus Lobaria pulmonaria and Its Green-Algal Photobiont

Werth¹,

Scheidegger²

2012

MPMI

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“…For both symbionts of L. pulmonaria , it has been shown that sample sizes of 20 individuals allows one to describe most of the allelic diversity at the population level, while within landscapes 300–400 samples and about 25–30 populations are sufficient (Werth ). The main goal of this study was to reconstruct the common phylogeographic patterns shared between the symbionts of L. pulmonaria and to localize centres of genetic differentiation on large spatial (and temporal) scales.…”

Section: Discussionmentioning

confidence: 99%

European phylogeography of the epiphytic lichen fungusLobaria pulmonariaand its green algal symbiont

et al. 2012

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In lichen symbiosis, fungal and algal partners form close associations, often codispersed by vegetative propagules. Due to the particular interdependence, processes such as colonization, dispersal or genetic drift are expected to result in congruent patterns of genetic structure in the symbionts. To study the population structure of an obligate symbiotic system in Europe, we genotyped the fungal and algal symbionts of the epiphytic lichen Lobaria pulmonaria at eight and seven microsatellite loci, respectively, and analysed about 4300 L. pulmonaria thalli from 142 populations from the species' European distribution range. Based on a centroid approach, which localizes centres of genetic differentiation with a high frequency of geographically restricted alleles, we identified the South Italy-Balkan region as the primary glacial refugial area of the lichen symbiosis. Procrustean rotation analysis and a distance congruence test between the fungal and algal population graphs indicated general concordance between the phylogeographies of the symbionts. The incongruent patterns found in areas of postglacial recolonization may show the presence of an additional refugial area for the fungal symbiont, and the impact that horizontal photobiont transmission and different mutation rates of the symbionts have on their genotypic associations at a continental scale.

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“…2005). On average, 31 thalli were collected per population, which has been found to be an appropriate number to resolve within‐population mycobiont and photobiont genetic structure (Werth 2010).…”

Section: Methodsmentioning

confidence: 99%

Vertical and horizontal photobiont transmission within populations of a lichen symbiosis

et al. 2012

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Lichens are widespread symbioses and play important roles in many terrestrial ecosystems. The genetic structure of lichens is the result of the association between fungal and algal populations constituting the lichen thallus. Using eight fungus- and seven alga-specific highly variable microsatellite markers on within-population spatial genetic data from 62 replicate populations across Europe, North America, Asia and Africa, we investigated the contributions of vertical and horizontal transmission of the photobiont to the genetic structure of the epiphytic lichen Lobaria pulmonaria. Based on pairwise comparisons of multilocus genotypes defined separately for the mycobiont and for the photobiont, we inferred the transmission mode of the photobiont and the relative contribution of somatic mutation and recombination. After constraining the analysis of one symbiont to pairs of individuals with genetically identical symbiotic partners, we found that 77% of fungal and 70% of algal pairs were represented by clones. Thus, the predominant dispersal mode was by means of symbiotic vegetative propagules (vertical transmission), which dispersed fungal and algal clones co-dependently over a short distance, thus shaping the spatial genetic structure up to distances of 20m. Evidence for somatic mutation generating genetic diversity was found in both symbionts, accounting for 30% of pairwise comparisons in the alga and 15% in the fungus. While the alga did not show statistically significant evidence of recombination, recombination accounted for 7.7% of fungal pairs with identical algae. This implies that, even in a mostly vegetatively reproducing species, horizontal transmission plays a role in shaping the symbiotic association, as shown in many coral and other symbioses in nature.

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Optimal sample sizes and allelic diversity in studies of the genetic variability of mycobiont and photobiont populations

Cited by 9 publications

References 36 publications

Congruent Genetic Structure in the Lichen-Forming Fungus Lobaria pulmonaria and Its Green-Algal Photobiont

Congruent Genetic Structure in the Lichen-Forming Fungus Lobaria pulmonaria and Its Green-Algal Photobiont

European phylogeography of the epiphytic lichen fungusLobaria pulmonariaand its green algal symbiont

Vertical and horizontal photobiont transmission within populations of a lichen symbiosis

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