Early molecular investigations of lichen-forming symbionts: 1986-2001*.

From the mid-1980s the symbionts in lichen associations, heterotrophic fungi and photosynthetic algae or cyanobacteria, were the subject of increasing numbers of molecular investigations. Many of the studies examined the phylogenetic placement of the individual symbiotic partners with their free-living relatives, refining their nomenclature and classification. Resulting phylogenies permitted the mapping of transitions to and from lichenization and stimulated discussion of the relative ease of gaining and losing symbiotic lifestyles. Comparing symbiont phylogenies both rejected strict cospeciation and mirrored phylogenies and hinted at more complex forces of coevolution, including symbiont switching and selection. Studies at the species and population levels examined patterns of species delimitation and geographic dispersion and processes such as gene flow, self-fertilization, and founder effect. Significant genetic variation often was associated with mobile elements, group I and spliceosomal introns. This review examines the influence of molecular investigation on lichenology during this first 15 years.