With an evolutionary history going back 300 million years, the flying spider-monkey fern is commonly regarded as supremely adaptable. Recently, it has been ravaged by a mysterious disease that Fu Chuen-hsu (back to camera) of the Forestry Research Institute hopes to unravel, thus saving the species from potential extinction. (photo by Chuang Kung-ju)
Lovers of lush mountain scenery are sure to be familiar with the flying spider-monkey tree fern. A common sight in the lower-altitude mountains of northern Taiwan, its appearance-the golden blades, tender buds coiled up like question marks, and the crisscross of leaf scars that appear on the trunk when the leafstalks fall away-hardly conforms to the typical image of a tree. This unusual plant is a portal to a long-forgotten ancient universe.
However, this 300-million-year-old survivor whose origins go back to the Carboniferous Period has been beset by an epidemic that has killed trees in the tens of thousands across the island. The reasons for the epidemic remain unclear, and will require greater attention.
Forestry Research Institute plant pathologist Fu Chuen-hsu first began getting reports about the spider-monkey ferns dying in large numbers back in 2006. In the beginning the cases were all situated in the mountains of northern Taiwan, but the affliction has since expanded to all of Taiwan and even the peripheral island Lanyu.
The acuteness of this strange disease has been nothing short of astonishing. The first marks of the disease are an abnormal withering of the leaves followed by the shriveling of new buds. Finally, the top of the tree begins to rot while the feather-shaped compound leaves completely fall away, leaving a barren, dying bark in their wake. Cutting into the pith of the tree, one notices that the healthy white-colored vascular bundle has given way to a putrescent deep brown. The whole process from onset through death takes no more than two months.
Since spider-monkey ferns reside far away from the dwellings of man, they don't pose much of a physical safety threat. Moreover, they don't figure much into the economy (although for a while they were being logged for use as a horticultural growing medium for mass sale overseas, the practice was later halted by conservationists), so plant pathologists are behind even in terms of their basic knowledge.
Fu explains that when a fern contracts an illness, many different strains of fungi can be present, making it difficult to determine the original pathogenic strain. Scientists clear up the matter by using Koch's Postulates, which involves inoculating a healthy specimen, and cultivating the disease-causing microbe in isolation. Through a process of elimination, the culprit can be distinguished from the later arrivals.
Earlier this year, Fu succeeded in isolating the fungus that caused the illness. To his fascination, it was a hitherto unnamed new strain. "All we know is that it belongs to the phylum Ascomycota. It's a kind of gloiospore, or slime spore-not airborne, requiring a living organism for dissemination. We've sent samples over to Academia Sinica where they will determine an official taxonomy."
As for the exact path to infection, Fu conjectures that there is a correlation with the behavior of certain bugs, such as egg laying. Infections tend to occur at certain times of year, with summer being the peak. Since there are healthy and diseased trees within close proximity of one another, "it eliminates the possibility of airborne spores as the mode of dissemination, because they would all be infected." He also suspects that this new fungus may have hitched a ride to Taiwan courtesy of illegally smuggled plants from overseas.
The Forestry Research Institute is scrambling desperately to develop an effective fungicide with which to check the epidemic's onslaught. In the regions where the scope of the infection is still rather small, they are recommending that contaminated plants be dug up so as to curtail further spread.
Guided by principles of biodiversity and conservation, the Forestry Research Institute has launched an unprecedented campaign to "harvest" the tree's spores, as a contingency plan.
"We still don't fully understand these trees, and if things keep up, we may never get that chance. They face the danger of extinction, which could then in turn affect the ecological balance in ways we can't predict. Harvesting their spores is a last-ditch effort so that, in the worst-case scenario, we can always replant them," says Fu, with obvious concern.