Present Address: Biodiversity and Climate Research Centre (BiK-F), Senckenberg Gesellschaft fuer Naturforschung, 60325 Frankfurt am Main, Germany.
Article first published online: 2 MAR 2012
© 2012 Blackwell Publishing Ltd
Volume 21, Issue 13, pages 3159–3172, July 2012
How to Cite
DAL GRANDE, F., WIDMER, I., WAGNER, H.H. and SCHEIDEGGER, C. (2012), Vertical and horizontal photobiont transmission within populations of a lichen symbiosis. Molecular Ecology, 21: 3159–3172. doi: 10.1111/j.1365-294X.2012.05482.x
- Issue published online: 21 JUN 2012
- Article first published online: 2 MAR 2012
- Received 8 Decemebr 2010; revision received 30 November 2011; accepted 1 January 2012
- ecological genetics;
- Lobaria pulmonaria;
- population genetics
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 20 m. 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.