PEI’s autumn leaves are gone, but there are still bright splashes of colour in the landscape. One of my favourites is the tiny but eye-catching British Soldier Lichen (Cladonia cristatella).
It’s not often that I remember the exact time and place I met a particular plant, fungus, or lichen for the first time, but I do with British Soldier Lichen. It was the fall of 1988, and I was a second-year biology student at UPEI, taking my first-ever botany course. We were on a field trip to Glenfinnan Bog, and the power poles along that side of the road were anchored inside wooden boxes on which British Soldier Lichens were growing. I had never before seen something so tiny but so beautiful, and I’ve been enamoured with them ever since.
British Soldiers are among our most common and easily identified lichens. You will recall from a previous post that lichens are a combination of a fungus and (usually) an alga. British Soldier’s eye-catching red caps are the fungal partner’s spore-producing structures, called ‘apothecia’.
If the fungal spores meet up with the right partner (in this case, the green alga Trebouxia erici) they may grow into new lichens. The chances of the spore landing in exactly the right place – next to the Trebouxia alga – under just the right conditions to join and form a new lichen are incredibly small. Fortunately, British Soldier Lichen hedges its bets and can also reproduce vegetatively: broken-off bits can grow into new lichens.
Nature is a model of efficiency where effort isn’t expended unless it’s needed, and nothing is wasted. Producing coloured pigments takes energy and so usually confers some competitive advantage to the organism. While we don’t know for sure why British Soldier Lichen’s apothecia are red, there are a few theories.
It’s plausible that the red colour may protect developing spores from sun damage. We see this in the botanical world all the time, such as the rusty hues of young Serviceberry leaves in spring or the twigs of Red Maple, Red-osier Dogwood, and some Willows. Alternate theories suggest the colour serves to either repel predators or attract them to help spread the spores. Given that some insects and mammals do eat British Soldier Lichen, the repellant theory doesn’t seem likely to me. I’d agree it’s possible that the colour is designed to attract predators to help spread spores or – more likely – bits of the lichen itself.
Lichens were among the first living things to recolonize PEI following the retreat of glaciers around 12,500 years ago. Massive ice sheets covered the Island for many millennia and left behind a landscape of bare rock and sediment. Because lichens get all their moisture and nutrients from the air and don’t need soil, they were able to start growing on this barren glacial till. They began the process of breaking it down, adding organic matter, and creating the soil that’s essential for plants and other living things. If you appreciate our soil and everything it produces, be sure to thank lichens!
While lichens as a group are post-glacial pioneers, British Soldier Lichen specifically wouldn’t have been. It prefers to grow on rotting wood (often in the company of other lichens or mosses) and so likely didn’t appear on the Island much before 9,000 years ago when the pollen record tells us the first woody vegetation started to appear.
British Soldiers Lichens are very slow growing, often just a millimetre or two per year. Slow growing things are usually long-lived and that’s the case here: British Solider Lichens can live for centuries. Of course, a lichen can’t be older than the substrate that supports it, and the Island’s history of land use means most of our lichens are not nearly as old as they could be. Even so, it’s possible that in some remote corner of our Island a lichen is slowly living its life as the oldest creature on PEI untamed!
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