The thing about science is that even with well-known things there’s always the possibility of learning something really new. Michael Ellis points to the humble lichen.
One of the very first things that you learn in Naturalist 101 school is about the relationships that exist in lichens.
The dogma for well over 200 years was that lichens consisted of two entirely different organisms that made up the whole. There is algae and a fungus that combine to make a separate third organism, very unlike the other two. The mnemonic device we all learned was “Alice algae took a lichen to Freddie fungus and now they live together in a natural relationship. He’s a fun guy.”
The algae was responsible for photosynthetic activity manufacturing the sugars that supplied energy for the fungus. The fungus for its part provided structural support, retention of water and nutrients. Lichens are pioneer plants, often found just hanging off the tree branches, on the ground or covering bare stones. The algae can live independently on its own but the fungus requires the algae to exist. This means Freddy is freeloading off of Alice. And one of our usual jokes was “…But we heard their relationship is on the rocks.” Yuck yuck.
Within the last several years, however, researchers have found that in many lichens there is an additional partner – a yeast – a single-celled member of the Kingdom Fungi. Somehow this third partner was overlooked for centuries as scientist peered through their microscopes. It was a striking find.