Birch tree with the rarely photographed resupinate pore surface of the sexual reproductive stage of obliquus. Photo courtesy of Tuomo Niemela. "Of course," you might say, "a needs exposure to the air in order to disperse its spores." But not so fast. Shortly after the fruiting body has forced open the bark, it loses almost all of its obvious morphology. That's because it's been colonized and then consumed by insects. In Finland, the larvae of the monophagous beetle Triplex russica seem to be among the primary consumers (Schigel, 2011), but this species is not known in North America. The North American consumers are doubtless either fungivores or parasitoids of after the tree has died ... sometimes as the fungivores—probably beetles and by Lawrence Millman long as several years after it has died. dipteran species, along with various So infrequently does the fruiting body larvae. he fruiting body of Inonotus grow on a living tree that on one of the So while the sterile conk of I. obliquus is so rarely few occasions when it did, the incident obliquus is a perennial, the fruiting encountered that the late was documented in a paper (Cha et al., body isn't even an annual. Indeed, it TSam Ristich once referred to it as a 2011). Fruiting bodies are seldom more usually doesn't last much longer than Holy Grail among (Ristich, than a foot long, so when a twelve foot a few days ... a very short time for pers. comm.). Few mycologists have fruiting body appeared on a yellow any fungus other than a fleshy one ever seen it; and if they have seen snag in October Mountain State like a Conocybe or a Psathyrella. For it, they probably dismissed it as an Forest in Massachusetts, that incident collection purposes, this is also a short unidentifiable mass of not necessarily was documented as well (Campbell time, since it's difficult to tell that the fungal tissue. By comparison, the and Davidson, 1938). fruiting body is actually a fruiting sterile conk (a.k.a., chaga), a rather Most resupinate polypores grow body with so little of it left. One of different sort of Holy Grail, is quite in contact with the soil or on the the diagnostic features of that fruiting common. That there's any connection undersides of logs; the fruiting body body is that its contextual hyphae stain between the two wasn't proposed of I. obliquus grows at a height on dark brown or black in KOH (Boulet, until as recently as 1938 (Campbell its host, invariably above the sterile 2003; Gilbertson and Ryvarden, 1986); and Davidson, 1938). This is hardly conk, and within the decayed in an insect-ravaged specimen, those surprising: who would suspect that a adjacent to the host's cambium—i.e., hyphae don't stain because they no cracked clinker-like protrusion and a directly under the bark. The only other longer exist. resupinate poroid basidiocarp usually species that forms a fruiting Fungal tissue contains choline, at a distance from each other would body under bark on a vertical or sloped B vitamins, lipids, and sterols, all belong to the same species? substrate is Inonotus andersonii, one of of which are important for the In North America, the host of I. the primary causes of mortality among growth and reproduction of insects obliquus is typically mature black, in the Southwest (Gilbertson and (Gilbertson, 1984). Yet certain fungi, paper, or yellow birch—all long-lived Ryvarden, 1986). But you seldom need rather than being passive sources of trees. Gray birch, which is relatively a rope and pitons or a stepladder to nutrition, seem to solicit insect diners. short-lived, is almost never a host. locate a specimen of I. andersonnii. Think of the Phallales (stinkhorns), for Infection of the tree occurs through Curious as it might already seem, instance. And while many polypores, the trunk, not the roots, and mostly the tale of I. obliquus now gets (to like other fungi, put up a defense through branch stubs and open quote Alice, of Wonderland fame) against mycophagous insects, some Nectria cankers. Like many other curiouser and curiouser: its yellow- of them would appear to be extending primary decayers, I. obliquus tends to brown, reddish-brown, or grayish- dinner invitations to them. Several die shortly after the demise and fall- brown basidiocarp erupts from the Gloeophyllum species possess an odor down of its host tree; once the tree has dead tree's bark in a manner that that makes them a termite attractant fallen, its mycelium is usually replaced recalls the explosion of the miniature (Schigel, pers. com.); Bjerkandera by secondary saprobes (Niemelä et alien from the astronaut's belly in the adusta is a magnet for thrips; and al., 1995). This helps to explain why sci-fi film Alien. So powerful is the Cryptoporus volvatus eagerly hosts the fruiting body is found on standing pressure immediately preceding this beetles on the inner part of its veil. But trees, but not very often on birch logs. eruption that the pattern of the inner with none of these species do insects The sterile conk (not to be confused, bark sometimes appears on the visible or their larvae wreak the same sort of as it often is, with a sclerotium) usually basidiocarp (Bondartsev, 1971). No havoc that they do on the fruiting body appears while the tree is still alive, but matter, because the fertile surface is of I. obliquus. the fruiting body doesn't appear until now exposed. "Many polypores are eaten by FUNGI Volume 5:3 11 insects, but in my experience none so destruction of the fruiting body seems parallel, thick-walled brown hyphae quickly as I. obliquus," Leif Ryvarden to indicate that insects are, if not a 3-5 microns across; generative hyphae has observed (Ryvarden, pers. com.). primary, at least an auxillary vector with simple septa; contextual hyphae Such alacrity suggests a chemical of spore dispersal. For a fungus that dark brown to black in KOH; basidia compound that says "eat me" to hungry disintegrates so quickly might need clavate, 15-20 x 6-9 (12) microns, insects and "be my guest" to egg- several spore dispersal strategies if it with 2 or 4 sterigmata; laying ones. The insects already dining wants to avoid extinction. hyaline, later pale yellow to pale on the fungus might also possess a The rarity of the I. obliquus fruiting yellowish-brown, negative in Melzer’s, pheromone that relays a "good eating" body has precluded study of its insect sometimes 1-guttulate, ellipsoid to message to insects of the same species. populations. Since we don't know subglobose, 6-10 x 5-7.5 microns. In return, all the fruiting body would exactly which insects they are, we also ACKNOWLEDGMENTS seem to ask of its diners is that they don't know if those insects might be serve as taxis for its basidiospores. equipped with mycangia (a special The insights of Leif Ryvarden, There are obvious arguments in favor spore pouch), which would make Tuomo Niemelä, Dmitri Schigel, of an anemophilous (wind-pollinated) them vehicles of spore transmission. and Donald Pfister helped greatly rather than an insect vectoring of the Likewise, this rarity has hampered in the writing of this paper. I’d also spores: a relatively high proportion study of the fruiting body itself. But like to thank the staff of the Farlow of fungi that depend on insects for rarity is perhaps not the appropriate Herbarium (Harvard), who—as is spore dispersal have spores with a word to describe a species that their custom—cheerfully located sugary slime coating (Ingold, 1953) typically hides under bark and grows obscure mycological tomes for me. or ones with spines or knobs, but high up on its substrate. A better word REFERENCES the spores of I. obliquus are neither might be elusive. And given such coated or ornamented; the violent elusiveness, this paper is necessarily Bondartsev, A.S. 1971. The manner in which the basidiocarp speculative, a compendium of Polyporaceae of European USSR and forces open the bark expresses a need "usuallys," "maybes," "probablys," and Caucasia. Program for Scientific for air and thus an anemophilous form "suggests." Despite this fact or maybe Translations: Jerusalem, Israel. of dispersal (Niemelä, pers. com); because of it, the paper is also intended Boulet, B. 2003. Les champignons and insects restricted to basidiocarp to be an introduction to a remarkable des arbres de l’est de l’Amerique du tissue normally do not invade wood fungal entity. Nord. Les Publications du Quebec. (Gilbertson, 1984), which would make Sainte-Foy: Quebec. DESCRIPTION a chemical attractant an unnecessary Campbell, W.A., and R.W. investment. Yet the unusually quick Basidiocarps short-lived, resupinate, Davidson. 1938. A Poria as the widely effused on fruiting stage of the fungus causing vertical substrates, the sterile conks on birch. Mycologia with tubes 30: 553-561. elongated to 2-3 Cha, J., S.Y. Lee, and K.W. Chun. cm; dimensions up 2011. Basidiocarp formation by to 30 cm x 6 cm, Inonotus obliquus on a living paper but occasionally birch tree. Forest Pathology 41: 163- much larger; at first 164. yellowish-brown or Gilbertson, R.L. 1984. Insects and fuscous, but quickly wood-rotting Basidiomycetes. In: becoming cracked Fungus-Insect Relationships, edited and dark reddish by M. Blackwell and Q. Wheeler. or blackish-brown; Columbia University Press: New York. at first somewhat Gilbertson, R.L., and L. Ryvarden. coriaceous-fleshy, 1986. North American Polypores. then drying brittle; Fungiflora: Oslo, Norway. context light Ingold, C.T. 1953. Dispersal in yellowish-brown, Fungi. Oxford University Press: faintly zonate, London, UK. continuing without Niemelä, T., P. Renvall, and R. change into the Pentilla. 1995. Interactions of fungi trama; no cystidia; in late stages of wood decomposition. pores round to Annales Botanici Fennici 32: 141-152. angular, 6-9 per Schigel, D.S. 2011. Polypore-beetle mm, but sometimes associations in Finland. Annales as few as 2-4 per Zoologici Fennici 48: 319-348. mm; hyphal system monomitic, with 12 FUNGI Volume 5:3