Peltigera membranacea – one of the species analysed in this study

One of the most successful alliances in the natural world often goes unnoticed. It involves either an alga or a bacterium that harvests energy from the sun to make its own nutrients. It shares this bounty with a fungus, which reciprocates by providing it with shelter. Together, the associates form a dual organism known as a lichen.

This alliance is so successful that lichens have colonised every continent, including Antarctica. They’re often ignored, but look closely, and you’ll find a hidden world of jellies, bushes, worms and pixie cups. Look even closer, and you’ll find a world of poison.

Ulla Kaasalainen from the University of Helsinki has discovered that one