Co-dispersal of symbionts in the lichen Cladonia stellaris inferred from genomic data

Abstract

We tested the congruence in dispersal patterns of the two main symbionts of the lichen Cladonia stellaris using genotyping-by-sequencing data. Based on 122 samples from eastern Canada, we recovered more than 21000 loci from the photobiont of C. stellaris. We described the population structure and estimate genetic diversity of the photobiont and identified the factors that contribute to explain genetic variation in both lichen partners. We also determined the identity of the dominant photobiont associated to C. stellaris using two molecular markers. Our results showed that C. stellaris is associated with Asterochloris glomerata, A. irregularis, and A. pseudoirregularis. Congruence in the genetic structure of photobiont and mycobiont were confirmed, suggesting co-dispersal of thallus fragments of C. stellaris. Genetic diversity of each symbiont was the factor that explained most of the genetic variation of the other symbiont, whereas geographical location and bioclimatic region seemed to have small or null explanatory power.