University of Montana ScholarWorks at University of Montana Ecosystem and Conservation Sciences Faculty Publications Ecosystem and Conservation Sciences 1997 Ophiostoma clavigerum is the Mycangial Fungus of the Jeffrey Pine Beetle, Dendroctonus jeffreyi Diana Six University of Montana - Missoula, [email protected] T. D. Paine Follow this and additional works at: https://scholarworks.umt.edu/decs_pubs Part of the Ecology and Evolutionary Biology Commons Let us know how access to this document benefits ou.y Recommended Citation Six, Diana and Paine, T. D., "Ophiostoma clavigerum is the Mycangial Fungus of the Jeffrey Pine Beetle, Dendroctonus jeffreyi" (1997). Ecosystem and Conservation Sciences Faculty Publications. 38. https://scholarworks.umt.edu/decs_pubs/38 This Article is brought to you for free and open access by the Ecosystem and Conservation Sciences at ScholarWorks at University of Montana. It has been accepted for inclusion in Ecosystem and Conservation Sciences Faculty Publications by an authorized administrator of ScholarWorks at University of Montana. For more information, please contact [email protected]. Mycologia,89(6), 1997, pp. 858-866. © 1997 by The New YorkBotanical Garden, Bronx, NY 10458-5126 Ophiostomaclavigerum is the mycangialfungus of the Jeffreypine beetle, Dendroctonusjeffreyi Diana L. Six1 Stock, 1982; Wood, 1982). The beetles are sympatric T. D. Paine over portionsof theirrange (Higby and Stock, 1982; Departmentof Entomology, University of California, Wood, 1982). Genetic evidence suggeststhat the Jef- Riverside,California 92521 freypine beetle and the mountain pine beetle have divergedrelatively recently from a common ancestor (Higby and Stock, 1982). Physiologicaltolerances of Abstract: Dendroctonusjeffreyi and D. ponderosaeare the twobeetles to resinchemical constituentsof their sibling species of bark beetles (Coleoptera: Scolyti- respectivehost tree species also support the desig- dae) withfew morphologicaland molecular genetic nation of these two beetles as separate species differences.The two species are believed to have di- (Smith,1963; 1965; Lanier and Wood, 1968). verged relativelyrecently. Dendroctonus jeffreyi colo- In both species, adults of both sexes carrysymbi- D. nizes onlyPinus jeffreyi,while ponderosaecolonizes otic fungiin mycangialocated on the maxillarycar- Pinus but not P. Adult up to thirteen spp., jeffreyi. dines (Whitneyand Farris, 1970; T. D. P., personal beetles of both D. and D. jeffreyi ponderosaecarry sym- observation). Mycangiaare structuresof the integu- biotic in located on the car- fungi mycangia maxillary ment specialized for carryingfungi (Batra, 1963; dines. Dendroctonus was known to ponderosae carry Francke-Grosmann,1967; Barras and Perry, 1971; two and 0. montium,in fungi,Ophiostoma clavigerum Happ et al., 1971). Although bark beetles and the its However,it was not knownwhich mycangia. fungi related ambrosia beetles are frequentlyassociated be carried D. were isolated might by jeffreyi.Fungi with a range of fungipassively disseminated on the from the of over 900 D. jeffreyicollected mycangia exoskeleton, more specific associations are main- froma large portion of its geographic range. Using tained between mycangia and the fungi associated and rates morphology,isozyme phenotypes, growth withthem. at differenttemperatures, all isolates fromD. jeffreyi The relationshipbetween bark beetles and mycan- mycangiawere determined to be 0. clavigerum;0. gial fungi has long been assumed to be mutualistic montiumwas neverisolated fromD. jeffreyimycangia. due to the presence of mycangiaand the prevalence Key Words: Ophiostomamontium, Dendroctonus of these associationsin Scolytidae.The fungusclearly ponderosae,bark beetles, mycangia,isozymes, Cole- benefitsthrough consistent transport to an ephem- optera, Scolytidae eral and relativelyuncommon resource,the phloem of dyingor newly-killedtrees. The benefit(s) gained by the beetle are less clear.It has been suggestedthat INTRODUCTION mycangialfungi may reduce the impactof antagonis- The Jeffreypine beetle, Dendroctonusjeffreyi Hop- tic blue-stainingfungi (Barras, 1970; Franklin,1970; kins, is a bark beetle exclusivelyattacking Pinus jef- Whitney,1971; Whitneyand Cobb, 1972, but see Ross et assistthe beetles in the de- freyiGrev. & Balf (Wood, 1982). Its geographicrange al., 1992), overcoming is roughlythat of its host tree, extending from the fenses of the host tree (Berryman,1972), alter the southern Oregon/northern California border to chemical or moisture composition of the phloem northernBaja California (Wood, 1982). The moun- (Nelson, 1934; Reid, 1961; Webb and Franklin,1978; tain pine beetle, Dendroctonus ponderosae, a poly- Wagner et al. 1979), or provide nutrientsor some phagous species utilizingup to thirteenPinus spp. other factor essential for the insect's development but not P jeffreyi,and D. jeffreyiare considered sib- and reproduction(Barras, 1973; Bridges,1983; Gold- ling species due to their almost-identicalmorpholo- hammeret al., 1990). gies and indistinguishablegallery systems (Higby and Dendroctonusponderosae is knownto carrytwo my- cangial fungi, Ophiostomaclavigerum (Robinson-Jef- Accepted for publicationJuly 14, 1997. frey& Davidson) Harringtonand 0. montium(Rum- 1 Correspondingauthor, present address: Universityof California, bold) von Arx (Whitneyand Farris,1970). The my- of EnvironmentalScience and Department Policy Management, not been Center for Biological Control, 201 Wellman Hall, Berkeley,CA cangial fungus carried by D. jeffreyihas 94720-3112.Email: sixstine(@earthlink.net identifiedpreviously, but a morphologicalsimilarity 858 This content downloaded from 150.131.192.151 on Mon, 3 Mar 2014 18:09:39 PM All use subject to JSTOR Terms and Conditions SIX AND PAINE: O. CLAVIGERUMIN D. JEFFREYIMYCANGIA 859 to 0. clavigerumhas been noted (Paine and Hanlon, collected from bark and from pheromone traps in 1994). Significantdifferences in tolerancesto various SawtoothNational RecreationArea, Idaho (Barbara host tree resin components were found between 0. Bentz, USDA Forest Service, Logan, Utah). Brood clavigerumcarried by D. ponderosaeand the morpho- adults,just prior to emergence,were collected from logicallysimilar fungus carried by D. jeffreyi(Paine the bark of infestedtrees by removingbark fromthe and Hanlon, 1994). The chemical environmentspre- entirecircumference of the trunkof treesfrom near sented by the host treesof the twobeetles differsub- soil level to a heightof ca. 2 m. Beetleswere collected stantially,and the fungi may have been selected for fromas manybroods and treesas possible per site in differenttolerances. Pinus jeffreyi,has n-heptane as order to gain a representativesample of mycangial its main resin component, while hosts of D. ponde- fungi.Only at one site were beetles taken froma sin- rosaehave monoterpenesand resinacids as major res- gle tree (Indiana Summit). Live beetles were held in components (Mirov,1929; Smith,1967; Anderson individuallyin microcentrifugetubes on ice and et al., 1969). transportedto the laboratory. Fungi, in general, are morphologicallysimple or- In the laboratory,each beetle was decapitated.The ganisms,and as such, morphologicaldifferences may head was dissectedto remove the maxillarycardines, be slightto nonexistentbetween related species even which contained the fungus-bearingmycangia. The long afteran initialspeciation event occurs (Brasier, cardines were surfacesterilized for two min in mod- 1986). Although the chemical environmentsof the ifiedWhite's solution (Barras, 1970) and submerged mycangialfungi in the host tree differ,the physical into malt agar and Ophiostomaselective agar (malt environmentswithin the host tree's tissuesare simi- agar with100 ppm cycloheximideand 100 ppm strep- lar. Also, both fungi apparentlyremain dependent tomycin) (Harrington, 1981). Once the mycangial upon the beetles for dispersal. Therefore,selection fungibegan to grow out fromthe mycangia,a plug pressure for morphological change may not be of agar containingthe funguswas removedfrom the strong,and indeed, selectionmay act to conserveex- growingedge and placed onto 2% water agar to fa- tant structures(e.g., arthropod disseminatedpropa- cilitatehyphal tipping.Fungal myceliagrow sparsely gules) while at the same time actingupon physiolog- on wateragar allowinghyphal tip culturesto be made ical traitsthat affectsurvival and exploitationof the with relativeease. Aftera few days growthon water chemical environmentof the tree. agar, hyphal tips were taken from each subculture There were two objectivesfor this study.First, we and placed on malt agar. wished to identifythe fungusor fungicarried in the Additionalstrains of 0. clavigerum(TABLE I) were mycangiaof D. jeffreyi.Many species of Dendroctonus acquired froma vouchered collection (T. C. Harring- including D. ponderosae,are known to carry more ton, Departmentof Plant Pathology,Iowa State Uni- than one species of mycangialfungus (Whitneyand versity,Ames, IA). Farris, 1970; Barras and Perry,1972; Bridges, 1983; Paine and Birch, 1983). Therefore,although isola- Morphological comparisons.-Conidiophores were tions from several beetles from a single population taken from2-3-wk old culturesof all mycangialiso- yielded a fungusmorphologically similar to 0. clavi- lates, mounted on glass microscope slides in lacto- gerum(T. D. P., unpublished data), it was not known phenol, visuallyinspected througha compound mi- if thiswas the onlyfungus carried byD. jeffreyiacross croscope (200X), and scored forthe presence of