Molecular phylogeny and symbiotic selectivity of the green algal genus Dictyochloropsis s.l. (Trebouxiophyceae): a polyphyletic and widespread group forming photobiont-mediated guilds in the lichen family Lobariaceae
- Dictyochloropsis s.l. is an ecologically important, common but little-studied genus of green algae. Here, we examined the diversity and host selectivity of algae attributed to this genus at both species-to-species and species-to-community levels.
- We conducted a molecular investigation of 15 cultured strains and several lichen photobionts, using 18S rRNA, rbcL and ITS sequence data. We further used seven alga-specific microsatellite markers to study algal sharing among fungi of the family Lobariaceae in two populations in Madeira and Taiwan (454 lichens).
- We found that the genus Dictyochloropsis s.l. is polyphyletic. Dictyochloropsis clade 1 comprises only free-living algae whereas Dictyochloropsis clade 2 includes lichenized algae as well as free-living algae. Fungal selectivity towards algae belonging to Dictyochloropsis clade 2 is high. Selectivity varies geographically, with photobionts being restricted to a single region. Finally, we showed that Dictyochloropsis clade 2 individuals are shared among different fungal hosts in communities of lichens of the Lobariaceae.
- As for other green algal lineages, there is a high amount of cryptic diversity in Dictyochloropsis. Furthermore, co-evolution between Dictyochloropsis clade 2 algae and representatives of the Lobariaceae is manifested at the community level, with several unrelated fungal species being horizontally connected by shared photobiont clones.