🧬 For 150 years, lichens were biology's textbook example of symbiosis: a fungus plus an alga, working together. Simple, elegant, settled science.
Except it wasn't. In 2016, genetic sequencing revealed a third partner hiding in plain sight - a basidiomycete yeast embedded in the lichen's outer cortex. Scientists had been looking at it through microscopes for over a century and assumed it was part of the host fungus.
This explains a mystery that frustrated mycologists for decades: why they could never grow a lichen in the lab from just the "known" two partners. The cultures always failed to develop the right shape or chemistry. The recipe was missing an ingredient.
The yeast's abundance correlates with variations in lichen body plans, suggesting it helps sculpt the very forms taxonomists had been cataloguing all along.
Source: Spribille et al. (2016), Science - science.org/doi/10.1126/scienc…
