Diana Six

Photo of Six, Diana

Diana Six

Professor of Forest Entomology/Pathology; Chair, Department of Ecosystems & Conservation Sciences

Personal Summary

Diana L. Six is Professor of Forest Entomology and Pathology in the Department of Ecosystem and Conservation Sciences at the University of Montana. Her primary research focuses on the evolution and maintenance of symbioses particularly those occurring among bark beetles, ambrosia beetles and fungi. Her research in this area includes several collaborative efforts with scientists in the US, South Africa, Europe, and Canada. She also conducts research on various aspects of bark beetle ecology and management, including investigations into the interactions of bark beetles with fire and forest stand structure and on interactions between an exotic pathogen (white pine blister rust) and a native insect (the mountain pine beetle) in high elevation whitebark pine ecosystems. Most recently, her focus has expanded to include effects of climate change, particularly on how changing temperatures may affect bark beetle symbioses with fungi and tree die offs in Africa.

Diana is also an associate editor for Symbiosis, Insects, the Journal of Economic Entomology, and the Western Journal of Applied Forestry .


A.S. Microbiology: 1986, Chaffey College, Alta Loma, CA High Honors
B.S. Agricultural Biology: 1990, California State Polytechnic University, Pomona, Magna cum laude
M.S. Entomology: 1992, University of California, Riverside
Ph.D. Entomology: 1997, University of California, Riverside Minor: Mycology
Postdoctoral Researcher: 1997. University of California, Berkeley

Research Interests

MEET MY STUDENTS and read about their research and what we do  Visit the Six lab

MEET THE USDA NATIONAL NEEDS FELLOWS working on critical issues in disturbance ecology at UM (http://www.cfc.umt.edu/NNFP/)

My research is both basic and applied. On the basic end of the spectrum, my interests are primarily in understanding ectosymbioses among bark and ambrosia beetles and fungi. These associations range from mutualistic to commensal to antagonisitic, and from facultative to obligate. Some fungi are highly specific and found only in association with a single beetle species, while others can be associated with many beetle hosts. In addition, most of these symbioses are multipartite, with the host beetle associated with two or more consistent partners. Mycangia, structures of the beetle integument that function in fungal transport, have evolved numerous times in the Scolytinae. The evolution of such complex specialized structures indicates a high degree of dependence of the beetles on their fungal partners and the fungi on their beetle partners. Unfortunately, the processes that have shaped current day beetle-fungus symbioses remain only poorly understood. Because many of these associations are multipartite, it is particularly difficult to determine origins of the partners and to detect the most critical factors shaping present day symbioses. Phylogeny, the degree and type of dependence on partners, mode of transmission (vertical vs. horizontal) of symbionts, effects of the abiotic environment, and interactions among symbionts and among symbionts and other members of the biotic community have all played important roles in determining the composition, fidelity, and longevity of associations between beetles and their fungal associates. In my research, I strive to determine how evolution and ecological processes have likely acted in concert to shape these fascinating, complex symbioses.

On the applied end of the spectrum, my research focuses on bark beetle ecology in relation to fire, stand structure, forest restoration and climate change. It also has recently expanded to investigate causes behind massive die-offs of trees across the globe including whitebark pine in North America and the giant Euphorbia tree in southern Africa.

Watch a video clip on collaborative research (John McCutcheon, Diana Six, Cathy Cripps) on the genomes of bark and ambrosia beetle-associated fungi (funded through the Institute of the Envrionment/NSF)

Check out a recent NYT article covering some of our research!

See vidoes, including one by me, from the Forests at Risk symposium (Al Gore Keynote)

Check out the new book on mountain pine beetle covering some of our research!


I am a member of several scientific societies including the Entomological Society of America, the Mycological Society of America, and the International Symbiosis Society. I sit on the Board of Directors for the Centre for Tree Health Biotechnology, Pretoria, South Africa and the Advisory Board for ISEFOR, a multi-nation, mutli-million dollar, EU-funded project on threats of exotics and climate change to European forests. I am also involved with several national and local conservation groups including Trout Unlimited (Board Member, West Slope Chapter) and Five Valleys Land Trust.

International Experience

Currently, I work several weeks each year in Africa, particulary with members of the Forest and Agriculture Biotechnology Institute (FABI) and the Centre for Tree Health Biotechnology, University of Pretoria, Pretoria, South Africa. This involves applied work with commercial plantation forestry and well as with conservation of indigenous forests. In the last three years, collaborations have expanded to include NUST and the University of Burinda, Zimbabwe. Field work is exciting and includes sites in Namibia, Botswana, South Africa and Zimbabwe. Nothing like working in a rhino preserve or on the banks of the Zambezi to keep you on your toes!


I LOVE to hike, backpack, cross country ski, and just about anything outdoors that respects nature and the land. I am an avid fly fisher and fly tier. Bodybuilding is my way to stay healthy and get rid of stress. I like to write and paint.

Selected Publications

Book chapters:

Six, D.L. 2003. Bark Beetle-Fungus Symbioses. Pp. 99-116. In: Insect Symbiosis. Eds. K. Bourtzis and T. A Miller. CRC Press.

Six, D.L. 2005. Population genetics of bark beetles and their associated blue-stain fungi with the use or molecular markers. In: Forest Pathology: From Genes to Landscapes. J.E. Lundquist, R.C. Hamelin, and C. Aquirre-Bravo, eds. American Phytopathological Society Press.

Peer-reviewed publications:

Six, D. L. and B. A. Mullens. 1996. Seasonal prevalence of Entomophthora muscae and introduction of Entomophthora schizophorae (Zygomycotina: Entomophthorales) in Musca domestica (Diptera: Muscidae) populations on California dairies. Biological Control 6: 315-323.

Six, D. L. and B. A. Mullens. 1996. Distance of conidial discharge of Entomophthora muscae and E. schizophorae conidia. Journal of Invertebrate Pathology 67: 253-258.

Six, D. L. and T. D. Paine. 1996. Leptographium pyrinum is a mycangial fungus of Dendroctonus adjunctus. Mycologia 88: 739-744.

Six, D. L. and T. D. Paine. 1996. A technique for the introduction of fungi to bark beetle mycangia. Journal of Entomological Science 31: 466-468.

Six, D. L. and T. D. Paine. 1997. Ophiostoma clavigerum is the mycangial fungus of the Jeffrey pine beetle, Dendroctonus jeffreyi (Coleoptera: Scolytidae). Mycologia 89: 858-866.

Six, D. L. and T. D. Paine. 1998. The effects of mycangial fungi on development and emergence of Dendroctonus ponderosae and D. jeffreyi. Environmental Entomology. 27: 1393-1401.

Six, D. L. and T. D. Paine. 1999. Phylogenetic comparison of the ascomycetes associated with the mycangia of Dendroctonus bark beetles. Annals of the Entomological Society of America 92: 159-166.

Six, D. L. and T. D. Paine. 1999. Allozyme diversity and gene flow in the bark beetle, Dendroctonus jeffreyi (Coleoptera: Scolytidae). Canadian Journal of Forest Research. 29: 315-323.

Six, D. L. and T. D. Paine. 1999. Allozyme diversity and gene flow in Ophiostoma clavigerum (Ophiostomatales: Ophiostomataceae), the mycangial fungus of the Jeffrey pine beetle, Dendroctonus jeffreyi (Coleoptera: Scolytidae). Canadian Journal of Forest Research 29: 324-331.

Six, D. L., P. Alaback, R. A. Winfree, D. Snyder, and A. Hagele. 2000. Pros and cons of using wilderness areas for biological research. Proceedings of the Wilderness Science in a Time of Change Conference. Missoula, MT. May 23-27, 1999.

Six, D.L., M. Vander Meer, T. H. DeLuca, and P. Kolb. 2002. Pine engraver, Ips pini (Say), colonization of logging residues created using alternative slash management systems in western Montana. Western Journal of Applied Forestry 17: 96-100.

Powell, H. D. W., S. Hejl, and D. L. Six. 2002. Measuring woodpecker food: a simple method for comparing wood-boring beetle abundance among fire-killed trees. J. Field Ornithol. 73: 130-140.

Six, D.L. 2003. A comparison of mycangial and phoretic fungi of individual mountain pine beetles. Canadian Journal of Forest Research. 33: 1331-1334.

Six, D.L. and B.J. Bentz. 2003. The fungi associated with the North American Spruce Beetle, Dendroctonus rufipennis. Canadian Journal of Forest Research. 33: 1815-1820.

Six, D.L., T.C. Harrington, J. Steimel, D. McNew, and T.D. Paine. 2003. Genetic relationships among Leptographium terebrantis and the mycangial fungi of three western Dendroctonus bark beetles. Mycologia 95: 781-792.

Dahlsten, D.L., D.L. Six, N. Erbilgen, K.F. Raffa, A.B. Lawson, and D.L. Rowney. 2003. Attraction of Ips pini (Coleoptera: Scolytidae) and its predators to various enantiomeric ratios of ipsdienol and lanierone in California: implications for the augmentation and conservation of natural enemies. Environmental Entomology 32: 1115-1122.

Six, D.L. and K. D. Klepzig. 2004. Dendroctonus bark beetles as model systems for the study of symbiosis. Symbiosis 37: 207-232.

Klepzig, K.D. and D.L. Six. 2004. Bark beetle fungal symbioses: Context dependency in complex associations. Symbiosis 37: 189-206.

Shelley, R.M. and D.L. Six. 2004. Discovery of the centipede, Scolopocrytops gracilis Wood, in Montana (Scolopendromorpha: Scolopocryptopidae). Western North American Naturalist 64: 257-258.

Dahlsten, D.L., D.L. Six, D.L. Rowney, A.B. Lawson, N. Erbilgin, and K.F. Raffa. 2004. Attraction of Ips pini (Coleoptera: Scolytidae) and its predators to natural attractants and synthetic semiochemicals: Implications for population monitoring in Northern California. Environmental Entomology. 33: 1554-1561.

Waring, K. M. and D.L. Six. 2005. Distribution of bark beetle attacks following whitebark pine restoration treatments. Western Journal of Applied Forestry. 20: 110-116.

Six, D.L. and M. Newcomb. 2005. A rapid method for rating white pine blister rust incidence, severity, and distribution within individual trees in whitebark pine. Northwest Science 79: 189-195.

Mueller, U., N. Gerardo, D. Aanen, D. L. Six, and T. Schultz. 2005. The evolution of agriculture in insects. Annual Review of Ecology, Evolution, and Systematics. 36: 563-595.

Six, D.L., Z.W. de Beer, R.A. Beaver, L. Visser, and M.J. Wingfield. 2005. Exotic invasive elm beetle, Scolytus kirschii, detected in South Africa. South African Journal of Science. 101: 229-232.

Jensen, J. and D. L. Six. 2006. Myrmecochory of the exotic plant, Centaurea maculosa (spotted knapweed), in western Montana: a potential mechanism enhancing invasiveness. Environmental Entomology 35: 326-331.

Bentz, B.J. and D.L. Six. 2006. Ergosterol content of three fungal species associated with Dendroctonus ponderosae and D. rufipennis (Coleoptera: Curculionidae, Scolytinae). Annals of the Entomological Society of America 99: 189-194.

Ortega, Y.K., K. S. McKelvey and D. L. Six. 2006. Invasion of an exotic forb impacts reproductive success and site fidelity of a migratory songbird. Oecologia 149: 340-351.

Adams, A.S. and D.L. Six. 2006. Temporal variation in mycophagy and prevalence of fungi associated with developmental stages of the mountain pine beetle, Dendroctonus ponderosae (Coleoptera: Curculionidae, Scolytinae). Environmental Entomology 36: 64-72.

Yen, T., D.L. Six, and E. Burke. 2006. A rapid culture-independent direct molecular method for detection of Phellinus pini from wood of lodgepole pine (Pinus contorta). Forest Products Journal 56: 107-110.

Six, D.L. and B.J. Bentz. 2007. Temperature determines symbiont abundance in a multipartite bark beetle-fungus ectosymbiosis. Microbial Ecology 54: 112-118.

Six, D.L. and J. C. Adams. 2007. Relationships between white pine blister rust and the selection of individual whitebark pine by the mountain pine beetle. Journal of Entomological Science 42: 345-353.

Lee, S., Breuil, C. Hamelin, R. and D.L. Six. 2007. Genetic diversity and the presence of two distinct groups in Ophiostoma clavigerum associated with the mountain pine beetle, Dendroctonus ponderosae in British Columbia and the northern Rocky Mountains. Phytopathology 97: 1177-1185.

Bleiker, K. and D.L. Six. 2007. Dietary benefits of fungal associates to an eruptive herbivore: potential implications of multiple associates on host population dynamics. Environmental Entomology 36: 1384-1396.

Adams, A.S. and D.L. Six. 2008. Detection of host habitat by parasitoids using cues associated with mycangial fungi of the mountain pine beetle, Dendroctonus ponderosae. The Canadian Entomologist 140: 124-127.

Boone, C.K., D.L. Six, Y. Zheng, and K. F. Raffa. 2008. Parasitoids and dipteran predators exploit volatiles from microbial symbionts to locate bark beetles. Environmental Entomology 37: 150-161.

Boone, C.K., D. L. Six, and K. F. Raffa. 2008. The enemy of my enemy is still my enemy: competitors add to predator load of primary bark beetles. Agricultural and Forest Management 10:411-421.

Adams, A.S., D.L. Six, S. Adams, and W. Holben. 2008. In vitro interactions between yeasts and bacteria and the fungal symbionts of the mountain pine beetle, Dendroctonus ponderosae. Microbial Ecology 56: 460-466.

Bleiker, K. and D.L. Six. 2008. Effects of water potential and solute on growth and interactions of two fungal symbionts of the mountain pine beetle. Mycological Research 113:3-15.

Bleiker, K. and D.L. Six. 2008. Competition and coexistence in a multi-partner mutualism: Interactions between two fungal symbionts of the mountain pine beetle in beetle-attacked trees. Microbial Ecology 57: 191-202.

Six, D.L., W. D. Stone., Z. W. de beer, S.W. Woolfolk, 2009. Ambrosiella beaveri, sp. nov., associated with and exotic ambrosia beetle, Xylosandrus mutilatus (Coleoptera: Curculionidae, Scolytinae) in Mississippi, USA. Antonie van Leeuwenhoek 96:17-29.

Six, D.L. and K. Skov. 2009. Response of bark beetles and their natural enemies to fire and fire surrogate treatments in mixed-conifer forests in western Montana. Forest Ecology and Management 258: 761-772.

Boone, C. K., D.L. Six, and K. Raffa. 2009. Assemblage of Hymenoptera arriving at logs colonized by Ips pini (Coleoptera: Curculionidae: Scolytinae) and its microbial symbionts in westrrn Montana. Canadian Entomologist 141: 172-199.

Raffa, K.F., B. Aukema, B.J. Bentz, A. Carroll, N. Erbilgin, D.A. Herms, J. A. Hicke., R. W. Hofstetter, S. Katovich, B. S. Lindgren, J. Logan, W. Mattson, A. S. Munson, D. J. Robison, D. L. Six, P. C. Tobin, P. A. Townsend, and K. F. Wallin. 2009. A literal use of “forest health” safeguards against misuse and misapplication. Journal of Forestry 107: 276-278.

Bleiker, K.P. S.E. Potter, C.R. Lauzon and D.L. Six. 2009. Transport of fungal symbionts by mountain pine beetles. Canadian Entomology 18: 55-59.

Hansen, A., D.L. Six and Y. Ortega. 2009. Comparison of ground beetle (Coleoptera: Carbaidae) assemblages in Rocky   Mountain savannas invaded and un-invaded by an exotic forb, spotted knapweed. Northwest Science 83: 348-360.

Six, D.L. 2009. Climate change and mutualism. Nature Reviews Microbiology 7: 686. Invited editorial.

Hatala, J.A., M.C. Dietze, R.L. Crabtree, K. Kendall, D.L. Six, and P.R. Moorcroft. 2011. An ecosystem-scale model for the spread of a host-specific forest pathogen in the Greater Yellowstone Ecosystem. Ecological Applications 21:1138-1153 


Six, D.L. and M. J. Wingfield. 2011. The role of phytopathogenicity in bark beetle-fungus symbioses: A challenge to the classic paradigm. Annual Review of Entomology 56: 255-272.

Wingfield, M. J., M. P. A. Coetzee, P. W. Crous, D. L. Six and B. D. Wingfield.  2011. Fungal phoenix rising from the ashes? IMA Fungus 1: 149-153.


Massoumi-Alamouti, S., D. L. Six, V. Wang, S. Diguistini, J. Bohlman, R.C. Hamelin, N. Feau, and C. Breuil. 2011. Gene genealogies reveal cryptic speciation and host-specificity for the pine fungal pathogen, Grosmannia clavigera. Microbial Ecology 20: 2581-2602.

Six, D.L, de Beer, ZW, Duong, T, Carroll, A. L. and M. J. Wingfield. 2011. Fungal associates of the lodgepole pine beetle, Dendroctonus murrayanae. Antonie van Leeuwenhoek 100: 231-244.

Six, D.L., M. Poulsen, A. K. Hansen, M. J. Wingfield, J. Roux, P. Eggleton, B. Slippers, and T. D. Paine. 2011. Anthropogenic effects on insect-microbial symbioses in forest and savanna ecosystems. Symbiosis 53: 101-121. Cover article

van der Linde, J. A., D. L. Six, and J. Roux. 2011. In press. New species of Gondwanamyces from dying Euphorbia trees in South Africa. Mycologia 104:574-584.

­­­­­­­­van der Linde, J.A, D. L Six, M. J. Wingfield, and J. Roux. 2011. Lasiodiplodia species associated with dying Euphorbia ingens in South Africa.  Southern Forests 73: 165-173. 

van der Linde, J.A., J. Roux, M.J. Wingfield, and D.L. Six. 2012. Die off of giant Euphorbia trees in South Africa: Symptoms and relationships to climate. South African Journal of Botany 83: 172-185.

Six, D.L. 2012. Ecological and Evolutionary determinants of bark beetle-fungus symbioses. Insects 3: 339-366.

In review:

Addison, A, J.A. Powell, D.L. Six, M. Moore, B. Bentz. 2012. The role of temperature variability in stabilizing the mountain pine beetle-fungus mutualism.

Dooley, E., J.A. Powell and D.L. Six. 2012. Mountain pine beetle productivity in lodgepole and whitebark pine after a region-wide cold weather event.

In prep:

Dooley, E, and D.L. Six. Severe white pine blister rust infection in whitebark pine alters mountain pine beetle attack and emergence rate, and size.

Friedman, M., B. Bentz, and D.L. Six. Temperature effects on growth and sporulation of mountain pine beetle symbiotic fungi.

Friedman, M. J.A. Powell and D.L. Six. Temperature effects on competition of mountain pine beetle symbiotic fungi.

Six, D.L. and E. Biber. Effects of management on mountain pine beetle outbreaks.

Six, D.L. Chemical and environmental mediation of interactions among bark beetles, microbial symbionts and natural enemies. 

Technical Reports: 

Bentz, B., J. Logan, J. MacMahon, C. D. Allen, M. Ayres, E. Berg, A. Carroll, M. Hansen, J. Hicke, L. Joyce, W. Macfarlane, S. Munson, J. Negrón, T. Paine, J. Powell, K. Raffa, J. Régnière, M. Reid, B. Romme, S. J. Seybold, D. Six, D. Tomback, J. Vandygriff, T. Veblen, M. White, J. Witcosky, D. Wood. Bark Beetle Outbreaks in Western North America: Causes and Consequences. 2009.  University of Utah Press. 44 pp.