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Lichens benefit from sunscreen

New research reveals that by developing natural sunscreen, a major group of lichens was able to colonise sun-exposed rocky habitats, leading to an ‘evolutionary radiation’.

Explosion in numbers of lichen species

A new study has revealed that about 100 million years ago there was an explosion in the number of species within the lichen family Teloschistaceae. Such events are believed by evolutionary biologists to be crucial for the formation of the diversity of life on earth. But unusually for such an ancient event, the researchers have been able to pin down the factors that caused it.

What are lichens?

Lichens are symbioses between fungi and photosynthesizing algae or cyanobacteria. In the Teloschistaceae, the fungi began producing natural sunscreen pigment, which protected them and their partners from the ravages of sunlight. Most yellow or orange coloured lichens belong to the Teloschistaceae, in fact, and their colour stems from the pigment that turns out to be the reason for their success.

Lichens shift to sunlit habitats

In the current study, researchers from Kew, and a number of collaborating institutions, reconstructed the evolutionary history of the Teloschistaceae using DNA sequences collected from present-day species. They were able to demonstrate that the evolution of sun-protecting pigments in this group coincided with an ecological shift: while their ancestors lived on bark, in shady habitats, these newly colourful lichens tended to live on rocks, and in the sun. By analysing the evolutionary tree that they had reconstructed for this group, the researchers were able to go on to show that the innovation of the pigments and the shift to sunlit habitats were the key factors that caused the Teloschistaceae to start diversifying at a higher rate.

Today there are more than 1,000 species of Teloschistaceae, although more are described on a regular basis. Like holidaymakers heading for the beach, these lichens were only able to thrive with the aid of sunblock.

This research was funded by the NSF (National Science Foundation).

Reference:

Gaya*, E., Fernández-Brime, S., Vargas, R., Lachlan, R. F., Gueidan, C., Ramírez-Mejía, M., Lutzoni, F. (2015). The adaptive radiation of lichen-forming Teloschistaceae is associated with sunscreening pigments and a bark-to-rock substrate shift. Proceedings of the National Academy of Sciences of the United States of America. DOI:10.1073/pnas.1507072112 Available online