JAN 29, 2021 8:05 AM PST

The surprising sex lives of lichen

Just like eavesdropping neighbors, scientists from Quebec's Université-Laval are peeping in on the shocking sex lives of reindeer lichens. As their name suggests, reindeer lichens (Cladonia stellaris) are organisms that compose a large part of reindeer diets; and like all lichen, they are a fascinating two-in-one organism, at once fungus and algae. Scientists are interested in these organisms because they are responsible for transferring nutrients throughout Quebec’s forests.

Perhaps the most intriguing information divulged from recent scientific observations of the lichens is their unexpected genetic diversity, which points towards more promiscuous habits than ecologists had previously realized. Before this recent study, which was published in the American Journal of Botany, reindeer lichens were thought to principally reproduce asexually.

"We were surprised because this species of reindeer lichen had always been considered mainly a clonal species that reproduce asexually," notes Marta Alonso-García, the paper's lead author and a postdoctoral fellow at the university. "It doesn't follow the expected pattern."

While scientists knew that the lichens could reproduce both sexually (by way of spores) or asexually (via cloning), the researchers say it is curious why the organisms appear to prefer sexual reproduction.

"Sexual reproduction is very costly," explains study co-author Felix Grewe, who is also the co-director of the Field Museum's Grainger Bioinformatics Center. "You have to find your partner, it's more difficult than reproducing asexually. But many organisms do it because when you have this combining and mixing of genetic traits, it enables you to weed out negative mutations long-term among other benefits."

Are the lichens perhaps seeking out these genetic advantages? To understand more, the group analyzed the genetic patterns between distinct geographic populations of the species, one from northern Quebec (Hudson Bay) and one from the South (Parc National des Grands-Jardins). They found that the populations differed genetically. Their analysis also considered the role that external factors, such as wildfire, had on genetic diversity.

"Wildfire is the most significant disturbance in the world's northernmost forests, and it plays a major role in determining the distribution and composition of plant communities," comments Alonso-García. "In Eastern North America, four successional vegetation stages are generally identified after a fire. During the first stage, crustose lichens and mosses colonize the burned surface. Subsequently, the soil is covered by cup and horn lichens. The landscape remains mostly uniform for around 20 years until the arrival of fruticose lichens which replace the previous vegetation. Cladonia stellaris arrives the last one, usually three or four decades after fire."

The researchers say they can use their bioinformatic findings to guide forest conservation efforts and determine where priorities should be placed. Alonso-García explains, "We have learned that time since the last fire does not necessarily mean more genetic diversity, so conservation strategies in boreal forests should take this into account. Prioritizing the protection of an area should not be based exclusively on its age. This is quite important because funding is usually limited, so we cannot carry out conservation activities in the entire forest," she concludes.

Sources: American Journal of Botany, Eureka Alert

About the Author
  • Kathryn is a curious world-traveller interested in the intersection between nature, culture, history, and people. She has worked for environmental education non-profits and is a Spanish/English interpreter.
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