A phone call to the Pentagon to talk about lichens gets a better response than one might expect. There’s no deputy assistant undersecretary for fungal/algal composite organisms, but the Air Force does keep a botanist at headquarters. And yes, part of his job is to attend to military-base lichens.
One of his subjects is Cladonia perforata, as close as the lichen world gets to having a celebrity.
These handfuls of yellow-gray branchings adapted to life on sand dunes earned the dubious honor in 1989 of becoming the first lichen proposed for the U.S. endangered species list.
C. perforata‘s tale reveals a window on biodiversity that doesn’t get opened much. The United States, with its 15,320 flowering plants, also bristles with 3,800 species of lichens. Yet the nation devotes nowhere near one conversation, career choice, or research dollar to lichens for every four dedicated to flowering plants. Despite the forward-thinking Air Force, it’s a flower-biased world out there.
Whether that will ever change remains to be seen. But the ongoing story of C. perforata—with populations that scientists have lost, new attention from geneticists, and a gardening crisis in the Air Force—is as close to the start of a new era as the lichen world has seen yet.
No plants these
If the Defense Department were to seek a deputy assistant in charge of lichens, it wouldn’t choose a botanist. Lichens aren’t plants. They aren’t animals, either. But each of the remaining kingdoms can contribute a species to a composite organism known as a lichen. These composites go by the names of the fungal partners.
Nearly one in five species in the fungal kingdom forms a composite with an alga, which is from the protist, or protoctist, kingdom. Some lichens include a third partner, one of the cyanobacteria, a.k.a. blue-green algae, from yet another kingdom. Whether this combination creates a mutually supportive partnership or slavery depends on the species, as well as on who’s doing the describing.
The novel chemistry of such partnerships has yielded compounds with antibiotic power, such as the active ingredient in the Usno salve sold in Europe. The Japanese paint industry turned to lichens for antimildew agents. Perfumes include lichen components, and the miniature world of model railroaders and architects, of course, draws part of its illusions from lichen-tufted “trees.”
Lichens also do plenty of ecological grunt work, breaking rock into particles of soil and feeding reindeer and other grazers in extreme climates. Lichens provide stalwart species for the living crust on the desert surface, and overall, they account for the dominant vegetation on 8 percent of land on Earth.
Utility aside, their exotic forms have charmed some good scientists—and military men. Lichen collector Geoge Llano, for example, served in the Air Force during the 1940s. In 1952, lichenologist Alexander Evans named a new species, C. perforata, that Llano had found on Santa Rosa Island in Florida. That island, off the state’s western panhandle, belongs in part to Eglin Air Force Base.
In subsequent years, the Air Force didn’t recruit many lichenologists, and by the late 1980s, biologists realized that no one had kept track of Llano’s find. Some lichen species range over several continents, but no such luck for C. perforata. Evans’ species sports easy-to-recognize perforations, like piercings in an ear lobe, that spot both the upper and lower surfaces of the branches. Yet 26 years after Evans named such an easy-to-notice species, biologists had found it in only 13 other locations worldwide, all in central Florida.
The locations are all bald patches in the oddball ecosystem called Florida scrub. This distinctive mix, dominated by pines and rosemary bushes, forms a tattered jungle along the white sand dunes of Lake Wales Ridge, about 100 miles south of Orlando. An estimated 40 to 60 percent of scrub organisms live only in this region, which may represent a relic of an ancient ecosystem.
In 1988, a state agency, the Florida Natural Areas Inventory, launched a search in the panhandle for the lost C. perforata. It wasn’t easy. Llano told searchers that he had revisited the original Santa Rosa Island spot in the 1950s and found it paved.
Evans also had collected on the panhandle. Maddeningly his labels just named Santa Rosa and a county, narrowing the search only to about half of the 48-mile-long barrier island. The searchers scoured the designated area, finding no trace of C. perforata.
At the other end of the island, however, they came upon C. perforata dotted over about a mile of dunes. The searchers assigned Evans to the group of great collectors whose taxonomy exceeds their geography.
The bad news about the 1989 rediscovery, from a lichen’s view, was that the panhandle’s only known C. perforata zone has a highway slicing through it.
Need for field work
Lost populations, confused labels, and the screaming need for field work sound like typical headaches of the nonflowering world to botanist Larry Morse of the Nature Conservancy in Arlington, Va. He, Melissa Karanosky, and various collaborators are working their way down checklists of all U.S. lichens, mosses, liverworts, and hornworts to assess which ones are rare.
The team takes into account publications, herbarium specimens, and advice from specialists in scoring a species’ status from 1, alarmingly rare, to 5, secure. Out of some 1,300 mosses in North America, about 20 percent rank 1 to 3, alarmingly rare to vulnerable, Karanosky reported this month at the Botany 2000 scientific meeting in Portland, Ore. About a third of liverworts, ground-hugging plants like strips of green ribbon, also merit concern, she said. For lichens, however, the conservancy team still has more than 3,500 species to check on. At the meeting, Karanosky appealed for help.
Morse clatters away at his keyboard searching for computer records of worrisome 1’s among the lichens. The team had found only three mentions of Pyrenula micheneri, the most recent from 1893. At this rate, Morse can’t even propose it for the endangered species list because he can’t prove there’s any left. “Possibly extinct,” he mutters as he types again, “but still worth searching for.”
Some gaps in a lichen’s range may signal gaps in data. Morse recalls giving a driving tour to a visiting lichenologist who specialized in a species known to grow on pine trees in just a few states. The conversation turned to the guest’s speciality.
“I picked the next side road and pulled into it,” Morse says. “I picked the next pine tree and pulled over.” The lichenologist checked the tree and recorded the first known occurrence of the species in Virginia. The first known occurrence in West Virginia, not far over the state line, dates from the same trip.
Florida biologists in the late 1980s grew worried about the vulnerability of C. perforata. Citrus groves were expanding, chewing at the edges of the last 15 percent of scrub habitat. In 1989, a biologist petitioned the U.S. Fish and Wildlife Service to list C. perforata as endangered.
For 2 years in a row, the service responded that the petition was “warranted” but outranked by species of more immediate importance.
C. perforata finally made lichen history in 1993 as the first of its kind to be declared endangered. Seven years later, the total of listed lichens has reached two.
When C. perforata was listed, biologists still knew virtually nothing about its life history. They didn’t even know how it spread, remembers Rebecca Yahr, now at Duke University in Durham, N.C. She had started studying the lichens in central Florida when she worked at the Archbold Biological Station at Lake Placid.
Lichens face a considerable challenge in reproducing and dispersing, since they have to coordinate the mechanics of several organisms. Getting the reproductive bits of the right partners to the right place—with partners from two or three kingdoms—makes the human mating game look laughably simple.
Lichens tackle the challenge in several ways. Sometimes, the fungus reproduces without its alga. A fungus tissue encounters a sexually compatible structure from a neighbor, mates, and then sprouts structures that release spores. Alternatively, a thread of fungus forgoes sex and bursts into spores on its own. The spores waft or hitchhike to some new location where there had better be the right species in search of a partner.
Some lichens don’t take such chances. They grow starter kits of a chunk of fungus paired with its alga, and these so-called soriedia break off to catch a ride on a creature or a breeze to a new frontier. Lichen bodies also fray, and simple wear-and-tear spreads fragments.
And C. perforata? “It’s never been seen to produce spores,” Yahr says. Nor has anyone caught it making soridia. After watching for it to reproduce conventionally since the early 1990s, she says, “I think it doesn’t.”
With no sex, no spores, and no colonizing soridia, how in the world does it grow beyond one spot? Small wear-and-tear fragments play a big part. “One of the ways this thing gets moved is by people and animals kicking it,” Yahr points out.
It’s certainly easy to kick. Unlike most lichens, C. perforata maintains only a loose grip on any surface. On the shifting sand dunes where Yahr’s lichens live, she has resorted to tethering the research subjects to poles with fishing line.
Dispersal by armadillo kick sounds as if it would be pretty limited, but Yahr is reevaluating the strategy. “It might actually be an adaptation not to disperse very much,” she suggests. If the species needs just a few good open dunes, then maybe it pays to stay close to them.
The sketchy knowledge of C. perforata biology flummoxed the Air Force in 1995, according to J. Douglas Ripley, one of the few botanists with a Pentagon address. As the Air Force’s natural resources manager, he oversees the nonhuman organisms, from antelopes to wiregrass, on the service’s 8 million acres.
That fall, Hurricane Opal slammed Eglin Air Force Base, denuding and flattening dunes. “We’re looking at a soccer field,” Ripley remembers. Seventy percent of the C. perforata community washed or blew away, some of it snagging in nearby trees.
Eglin includes a white-collar prison, so base officials sent inmates to rescue lichens stranded in tree branches. The prisoners filled sacks, which piled up in base refrigerators.
Replanting the lichens proved astonishingly difficult. Yahr and Smithsonian lichenologist Paula DePriest joined the effort. Yahr snuggled some of the lichens back into the sand, but most languished and died. In retrospect, she wonders whether the saltwater drenching poisoned them and much of their sand dune habitat.
The researchers tried more elaborate techniques. Selecting lichens from the refrigerated bags, “I used a hair dryer to get them nice and crunchy,” Yahr explains. Then, she ground them to a powder using “your average $3 food mill from Kroger’s” and scattered the lichen dust over the sand.
She’d read about pulverized lichens restoring a stand of reindeer moss in Norway. However, 5 years later at Eglin, Yahr sees no signs of lichen life and has given up on grinding. Yahr’s finally beginning to see lichens start to take hold when she sets out unpowdered fragments in places where they’d died before. After the long struggle, she muses that the best response to such a disaster may be just to sit back and wait. A big storm “is a good and a bad thing,” she says. It may have wiped out a huge chunk of the population, but it also exposed a lot of open sand for the survivors to colonize. She speculates that fire may serve the same function in the central-Florida lichens.
That image of a homebody species in need of occasional disasters helps Yahr make sense of the genetic uniformity she’s finding. Using two methods, she’s discovering practically no diversity within each of three sample patches in central Florida. That’s what she’d expect from a population that repeatedly shrinks to a few individuals and then regrows.
The Eglin population poses more of a mystery, she says. Her results so far suggest that it has more diversity than the others.
In case anybody was getting notions that Ripley could replenish his lichens with transplants from central Florida, Yahr’s genetic work zapped that hope. The lineages of the lichen she identified in central Florida patches differ sharply—in both fungal and algal partners—from Eglin’s lichen. Mingling the populations might swamp what whispers of diversity remain.
The lineage identifications intrigue DePriest, she says, because in one place in central Florida the fungus of one of the strains seems to have kidnapped the other’s alga.
Genetic work suggests that throughout the lichen world, fungi have been co-opting and swapping algae. Researchers checking sequences of DNA have found seven times as much variation in fungi as in the algae—a lot of fungi are partnering with not so many algae.
De Priest unfolds a diagram of two family trees, one algal and one fungal. Lines between the trees match a fungus to its algal partner. A casual bystander might guess that the two partners’ trees would branch in the same patterns. However, “it’s all messed up,” as DePriest puts it.
Lines connecting partners zig from closely related fungi to disparate algae and vice versa, jumping and crisscrossing to form a big drunken asterisk. Any pair of lichen family trees she’s ever seen has yielded the same mishmash.
“It’s like farmers in Kansas,” she speculates. The farmers don’t stick to raising their personal strain of corn, one for each family. These optimizing, algae-poaching fungi don’t sound like the happy, egalitarian partners of children’s nature books. “Some people want to believe lichens are totally cooperative,” DePriest acknowledges. However, fungi could be enslaving their algae, sucking up nutrients while providing precious little benefit. Or the algae may be parasites, each essentially a disease of some victimized fungus.
European lichenologists, with more exposure to socialist influences, “tend to like cooperation,” she teases. “I think Americans like winners and opportunists.”
Such issues can work their way down to the basics of what a lichen really is. The modern answer, she explains, dashes the vision of lichens as a discrete group of organisms that share a history, as flowering plants do. Instead, lichenization as a lifestyle can pop up in a variety of twigs in the family tree.
Previous scrutiny of the lichen structure had suggested that conclusion, but DePriest and an international team of experts published molecular evidence just 5 years ago. Their work used the varying similarity of DNA sequences to construct a fungal family tree. The fungi that form lichens sprout separately six times.
If anything, the diverse origins of lichenization add interest in their conservation: There’s a lot of diversity to save.
Not that it’s going to be easy. Even the resources of the Pentagon failed for years to get its lichens growing again on the ground.
Ripley, however, has weathered his share of conservation crises. During the lichen-resuscitation episode, another of Ripley’s projects turned up a small patch of Sandplain gerardia, a federally listed endangered flower, at Andrews Air Force Base in Maryland. That find stalled golf course expansion for 2 years and eventually required a traumatic repositioning of the 13th tee.
After that, working on lichens may not seem so hard.