One of the oddities of taxonomy is that lichens get species names, even though they’re not organisms. What might look like a fungus clinging to a rock is, in fact, a community of fungi and algae living in symbiosis. The alga provides food to its fungal host. In return, the fungus supplies water and nutrients. But an alga does not need to live as part of a lichen. So are there other benefits? Beatriz Fernández-Marín and colleagues examined the association between the lichen-forming fungus Mastodia tessellata (Verrucariaceae) and different species of Prasiola (Trebouxiophyceae). Mastodia is no ordinary lichen, which explains the team went to the Antarctic to study it.

“Mastodia is an intriguing case within lichen species and since long has been confronting lichenologists, and challenging ‘the concept of lichen’ itself,” Fernández-Marín said. “The fact of having macro- (e.g. visible by bare eye) instead of microscopic terrestrial algae within the lichen symbiosis is very rare among lichens and enables us to study them under natural conditions easily. In addition, both the free-living and the lichenized forms are co-habiting in the same microenvironment. This crossover makes the species a perfect case study to understand how being part of a lichen changes the life of an alga.”

“The ecological preferences of Mastodia are the second remarkable reason: it has a bipolar distribution, with an ancient austral origin and a later migration to the northern hemisphere (as nicely evaluated by two of our co-authors in a very recent work), and is always found in cold, wet, coastal habitats. This was particularly interesting for us because the context of our overall project is that we are trying to understand how desiccation and freezing tolerances are possible in some photosynthetic organisms. One of our objectives was to deepen our understanding of how lichens can survive freezing temperatures when wet. Among the different locations where Mastodia can be found, Antarctica offers the additional advantage of being a pretty pristine natural environment, where these organisms have not suffered the influence of humans, at least not significantly.  So we can study them as they behave really in the wild.”