The magazine Bay Nature is new to us, brought to our attention thanks to a friend from that part of the world. It comes via this particular article, which touches on several topics–fungi, birds, conservation and Bay Area awesomeness–commonly seen in our own pages in the last five years. Have a read below and if you like it go read the remainder on their website:
How the surprising union between a fungus and an alga raises questions about the nature of identity
by Elizabeth Lopatto
In July, Governor Jerry Brown signed into law a bill declaring the lace lichen—found along the Pacific coast and throughout the coast ranges—the state lichen. As of January 1, 2016, California will be the first state ever to designate a lichen as a state symbol.
Lace lichen, Ramalina menziesii, is easily recognized. It is pale green and dangles in strips from trees. It’s sometimes confused with Old Man’s Beard (Usnea sp.), which is also pale green and dangly. Lace lichen’s range stretches from Alaska to Baja California. It’s an important food for deer; it also serves as material for birds’ nests. I see it once, in researching this story, when naturalist Morgan Evans, a former student naturalist aide at Tilden Nature Area in the East Bay hills, removes it from her backpack and spreads it out. Evans is a pleasant and patient woman, whose true love is fungi. Her interest in lichens is an extension of that, she says. Anyway, she found some lace lichen growing in Morgan Territory Regional Park. She figured I’d want to see it and there isn’t much growing in Tilden that she knows of. She hands me the lichen, which feels strangely plasticine. It’s pale green—she wetted it so it wouldn’t crumble when she transported it—and dangles impressively, at least six inches long. Lace lichen can grow as long as a meter, and it has a netted structure that looks, to me at least, more like fishnet stockings than lace. Perhaps fishnet-stocking lichen would be a little too racy a nickname.
Before I tell you more, though, a disclaimer: It turns out lichen identity is fraught with existential issues, not least of which is that lichens are a union between two separate organisms. Basically lichens are fungi—that kingdom of non-plant, non-animal organisms—that have learned to tend algal or cyanobacteria cells like a farmer does a crop. Sometimes called a photobiont, the alga or cyanobacterium makes food for the fungus, manufacturing sugars from sunlight and carbon dioxide. In return, the fungus gives the algae a place to live, and in so doing, grows its fungal threads into the bodies of the photobiont, making it easier for the fungus to tap into the nutrients its partner produces. Though photobionts may live free of their keepers—and some do in Tilden, I learn—the fungus’ survival depends on the photobiont. Of the world’s roughly 25,000 lichen species, only a couple can live as a fungussans its partner.
But scientists have probed what happens to the two organisms when separated in a lab and grown in cultures. For instance, Schizoxylon albescens is a fungus that can occur both as a lichen and as a solo act, a group of Austrian scientists found in 2011. A genetic analysis showed that the two versions of the fungus are not separate species. Studies have also revealed that once a lichen is broken into its constituent parts in the lab, they can’t be reunited. And researchers have no idea why. Maybe it’s because lichenization—the little-understood process that binds fungal spores and photobionts to create a lichen—may depend on yet another set of organisms: bacteria. It’s possible that bacteria are essential to lichens’ existence, making lichens more like an ecosystem than just a two-party party.
Anyway, if you are feeling uneasy about identity, this is only going to get worse, as Evans tells me. “Species? That’s difficult,” she says. It’s hard to know precisely what species a lichen is without a hand lens or, in many cases, chemicals or a microscope, because what distinguishes different types of lichen are very tiny structures. Essentially, telling them apart comes down to examining the lichen’s structure by microscope; the chemicals help identify, by the color reaction, the presence or absence of chemical compounds, the signatures of various species. This necessity presents trouble for an amateur lichenologist, who might not want to tote a heavy guidebook—much less a microscope—into the field. Today here in Tilden, we have a hand lens, laminated papers, and a small guidebook from the California Lichen Society, and we’re going to do our best. You can usually at least get to genus this way.
As for the lichen I am about to attempt to identify: What is identity? I have a few things in common with the fungal partner in the lichen system. For instance, not all the nutrients I absorb are due to my own digestion. Plenty of the cells in and around my body that allow me to operate aren’t my cells at all. I have many bacteria—and some fungi—in what’s called my microbiota, and they’re useful for my continued health. Take gut bacteria, for instance. Most of us don’t notice they’re doing anything until we take a round of antibiotics. Antibiotics are indiscriminate—they’ll kill our helpful bacteria along with whatever’s ailing us. Many people suffer from diarrhea as a result of their lost gut bacteria, since they suddenly can’t process food as well; worse, without our helpers around, our guts become better homes for harmful bacteria like Clostridium difficile (also known as C. diff). I do not mean to denigrate the lichen’s status as a weird compound organism; it’s just that everything is a habitat—Tilden, your neighborhood, your stomach, your own face. It gets worse: Our genes show evidence that we actually absorb the genomes of some viruses into human DNA—if a sperm or egg cell is infected, the virus is incorporated into the fetus. Identity works only so long as you don’t look very hard at it; I have, at present, no explanation for how it functions whatsoever.
Are lichens fungus or alga? Oh, they are both, until it comes to the taxonomy. At this point we get down to business: They’re identified by the fungus. A fungus that, remember, occasionally sticks threads into its so-called partner, to more easily soak up nutrients. So, a fungus with digestive cells. In the middle of its structure. Does this setup sound familiar? A little, right? I tell this to Evans and she laughs. “Right!” she says. “We’re all composite organisms.”
She tucks away her lace lichen and we head out into the Tilden Nature Area to find some more. We won’t need to walk far or look very hard…
Read the whole article here.