Tom Horton

Students interested in joining the lab should contact me via email at:



Some useful links

  • Fungal Environmental Sampling and Informatics Network (FESIN)
  • Use-Friendly Nordic ITS Ectomycorrhiza Database (UNITE)
  • DEEMY: An information system for characterization and DEtermination of EctoMYcorrhizae
  • Photos galore at the Mycorrhizal Image Exchange page (many, but not all, have broken links -- sorry!)

My research interests:

All of my research is applicable to various issues in conservation biology of ectomycorrhizal fungi and plants. Mycorrhizal fungi are primarily below ground, cryptic and essentially considered microbial, leading plant and ecosystem ecologists to largely 'black-box' their roles in plant communities and ecosystem dynamics. A second focus of mine is the development and use of PCR-based techniques to identify fungi directly from mycorrhizal root tips and soil hyphae, thus giving us an ability to peek into the black-box (see Horton and Bruns, 2001). It is amazing to me that most textbooks barely mention mycorrhizal symbioses. Indeed, many ecologists still consider mutualisms as special cases (acacia ants, orchid moths). Part of this bias comes from the fact that models of mutualisms predict that they are unstable and therefore should not be common (there are probably some socio-political issues here as well!!). But four examples of very stable mutualisms should put that misunderstanding to rest: chloroplasts in plant cells, mitochondria in eukaryotic cells, N-fixing bacteria in plant roots, and lichens. Further, around 80% of all plants associate with mycorrhizal fungi that are typically mutualistic, so mycorrhizal mutualisms are a fifth case demonstrating the ubiquity of mutualisms in nature. Are mycorrhizal symbioses evolutionarily stable? Mycorrhizal fungi have been associated with plants since they colonized land over 400 million years ago. Oh...and just to check whether you are mycocentric or phytocentric, when you read 'they' in the previous sentence, do you think of fungi or plants?

Current projects: updated May-2012

At the risk of pigeonholing the breadth of their work, my graduate students have investigated or are investigating the role of mycorrhizal fungi in plant community dynamics (Sara Ashkannejhad, Tera Galante, Jeremy Hayward, Mikey O'Brien, Yazmin Rivera), restoration ecology (Kris Dulmer, Chris Hazard, Erin Page, Sam Tourtelott), and ecosystem dynamics (Becka Walling) and development of phylogenetic approaches aimed at elucidating functional roles of EMF (Joe Vineis). See summaries of projects below.

Past projects (Gone but not forgotten....send money now!)

Students and Visiting Scholars

Current Grads
Current Undergrads
Former Grads
Former Undergrads

Visiting Scholars

Jeremy Hayward (PhD) Jordan Devereaux Melanie Antonik (MS) Jed Cappellazzi (Lab tech/Honors Student) Tina Bell

Elisabeth Holmes (MPS)

Christine Elliot Sara Ashkannejhad (MS) Joelle Chille Michael Booth
Sam Tourtellot (MS)   Kris Dulmer (MS) Dan Clune Alix Contosta
Rebecca Walling (MS)   Tera Galante (MS) Anna Conrad (REU) Stephen Leduc
    Karen Gentile (MPS) Ashley Conrad

Kirsten Føns

    Chris Hazard (MS) Ariel Cowan Amy Karpati
    Mike Hough (Co-advised with Greg McGee; MS) Erik Facteau Martin Nuñez
    Samantha Knowlden (MPS) Dave Gonnella Madeleine Osborn
    Mike O'Brien (MS) Kim Hevers Maria Moskalenko
    Marian Orlousky (MPS) Kali Lader Andy Ouimette
    Erin Page (Co-advised with Rick Smardon; MS) Katie Lawson (REU) Dave VanEarden
    Yazmin Rivera (PhD) Gwen Lennox  
    Lori Sopchak (MPS) Lindsay Miller  
    Marie Terlizzi (MPS) Dave Muska  
    Joe Vineis (MS) Alex Newman  
      Allison Oakes  
      Alena Oliver  
      Andrea Reinhardt  
      Tanya Rommel  
      Jesse Spitzer  
      Erin Sweeney  
      Eva Sztechmiler  
      Justin West  
      Angela Wright  



Peer-reviewed articles

LeDuc SD, Lilleskov EA, Horton TR, Rothstein DE (2013) Ectomycorrhizal fungal succession coincides with shifts in organic nitrogen availability and canopy closure in post-wildfire jack pine forests. Oecologia: 172: 257-269.

Kennedy PR, Smith DP, Horton TR, Molina RJ (2012) Arbutus menziesii (Ericaceae) facilitates regeneration dynamics in mixed evergreen forests by pormoting mycorrhizal fungal diversity and host connectivity. American Journal of Botany 99:1691-1701.

Hayward J, Horton TR. (2012) Edaphic factors do not govern the ectomycorrhizal specificity of Pisonia grandis (Nyctaginaceae). Mycorrhiza. 10.1007/s00572-012-0442-2. Mycorrhiza 22:647-652.

Hazard C, Lilleskov EA, Horton TR. (2012) Is rarity of pinedrops (Pterospora andromeda) in eastern North America linked to rarity of its unique mycorrhizal host? DOI 10.1007/s00572-011-0414-y. Mycorrhiza 22: 393-402.

Galante TE, Horton TR, Swaney D (2011) 95% of basidiospores fall within one meter of the cap- a field and modeling based study. Mycologia 103:1175-1183.

Karpati AS, Handel SN, Dighton J, Horton TR (2011) Quercus rubra-associated ectomycorrhizal fungal communities of disturbed
urban sites and mature forests. Mycorrhiza. Mycorrhiza 21:537-547.

Molina R, Horton TR, Trappe JM, Marcot BG (2011) Addressing uncertainty: How to conserve and manage rare or little known fungi. Fungal Ecology 4: 134-146.

Lilleskov EA, Hobbie EA, Horton TR (2011) Conservation of ectomycorrhizal fungi: exploring the linkages between functional and taxonomic responses to anthropogenic N deposition. Fungal Ecology 4: 174-183.

O'Brien MJ, Gomola CE, Horton TR (2011) The effect of forest soil and community composition on ectomycorrhizal colonization and seedling growth. Plant Soil 341: 321-331.

van der Heijden MGA, Horton TR (2009) Socialism in soil? The importance of mycorrhizal fungal networks for facilitation in natural ecosystems. Journal of Ecology 97:1139-1150. (Special feature on facilitation in plant communities).

Nuñez MTA, Horton TR, Simberloff D (2009) Lack of belowground mutualisms hinders Pinaceae invasions. Ecology 90:2352-2359.

Horton TR (2006) The number of nuclei in basidiospores of 63 species of ectomycorrhizal Homobasidiomycetes. Mycologia 98: 233-238.

Ashkannejhad S, Horton TR (2006) Ectomycorrhizal ecology under primary succession on coastal sand dunes: interactions involving Pinus contorta, suilloid fungi and deer. New Phytologist 169:345-354.

Becerra A, Zak MR, Horton TR, Micolini J (2005) Ectomycorrhizal and arbuscular mycorrhizal colonization of Alnus acuminata from Calilegua National Park (Argentina). Mycorrhiza 15: 525-531.

Horton TR, Molina R, Hood K (2005) Douglas-fir ectomycorrhizae in 40 and 400 year-old stands: mycobiont availability to late successional western hemlock. Mycorrhiza 15: 393-403.

Fujimura KE, Smith JE, Horton TR, Weber NS, Spatafora JW (2005) Pezizalean mycorrhizas and sporocarps in ponderosa pine (Pinus ponderosa) after prescribed fires in eastern Oregon, USA. Mycorrhiza 15: 79-86.

Nouhra ER, Horton TR, Cazares E, Castellano M (2005) Morphological and molecular characterization of selected Ramaria mycorrhizae. Mycorrhiza 15: 55-59.

Lilleskov EA, Bruns TD, Horton TR, Taylor DL, Grogan P (2004) Detection of forest stand-level spatial structure in ectomycorrhizal fungal communities. FEMS Microbiology Ecology 49: 319-332.

Horton TR (2002) Molecular approaches to ectomycorrhizal diversity studies: variation in ITS at a local scale . Plant and Soil 244: 29-39.

Becerra A, Daniele G, Domínguez L, Nouhra E and Horton T (2002) Ectomycorrhizae between Alnus acuminata H.B.K. and Naucoria escharoides (Fr.:Fr.) Kummer from Argentina. Mycorrhiza: 12:61-66.

Lilleskov EA, Fahey TJ, Horton TR, Lovett GM (2002) Nitrogen deposition and ectomycorrhizal fungal communities: a belowground view from Alaska. Ecology 83: 104 - 115.

Horton, Thomas R. & Bruns, Thomas D (2001)  The molecular revolution in ectomycorrhizal ecology: peeking into the black-box. Molecular Ecology 10 (8): 1855-1871.

Chapela IH, Osher LJ, Horton TR, Henn MR (2001) Ectomycorrhizal fungi introduced with exotic pine plantations induce soil carbon depletion. Soils Biology and Biochemistry 33: 1733-1740.

Baar J, Horton TR, Kretzer A, Bruns TD (1999) Mycorrhizal recolonization of Pinus muricata from resistant propagules after a stand-replacing wildfire . New Phytologist 143: 409-418.

Allen MF, Trappe JM, Horton TR (1999) NATS truffle and truffle-like fungi 8: Rhizopogon mengeisp. nov. (Boletaceae, Basidiomycota). Mycotaxon 70: 149-152.

Stendell ER, Horton TR, Bruns TD (1999) Early effects of prescribed fire on the structure of the ectomycorrhizal fungal community in a Sierra Nevada ponderosa pine forest. Mycological Research 103: 1353-1359.

Horton TR, Bruns TD, and Parker TV (1999) Ectomycorrhizal fungi associated with Arctostaphylos contribute to Pseudotsuga menziesii establishment. Canadian Journal of Botany 77: 93-102.

Horton TR, Bruns TD (1998) Multiple host fungi are the most frequent and abundant ectomycorrhizal types in a mixed stand of Douglas fir (Pseudotsuga menziesii D. Don) and bishop pine (Pinus muricata D. Don). New Phytologist 139(2): 331-339.

Horton TR, Cázares E, Bruns TD (1998) Ectomycorrhizal, vesicular-arbuscular and dark septate fungal colonization of bishop pine (Pinus muricata) seedlings in the first five months of growth after wildfire. Mycorrhiza 8:11-18.

Bruns TD, Szaro TM, Gardes M, Cullings KW, Pan JJ, Taylor DL, Horton TR, Kretzer A, Garbelotto M, Li Y. (1998) A sequence database for the identification of ectomycorrhizal Basidiomycetes by phylogenetic analysis.   Molecular Ecology 7: 257-272.


Book Chapters, Comments and Miscellaneous other articles

Briggs RD, Horton TR (2011) Out of sight, underground: forest health, edapthic factors, and mycorrhizae. In: Forest Health. Castello J, Teale S. Eds. Cambridge University Press.

Horton TR, Arnold AE, Bruns TD (2008) FESIN workshops at ESA - the mycelial network grows. Mycorrhiza 19:283-28

Horton TR, van der Heijden M (2008) The role of symbioses in seedling establishment and survival. In: Seedling Ecology and Evolution. Leck M, Parker VT, Simpson B, Eds. Cambridge University Press.

Bidartondo et al. (2008) Preserving accuracy in GenBank. Science 319: 1616 (This is a letter signed by many.)

Hobbie EA, Horton TR (2007) Evidence that saprotrophic fungi mobilise carbon and mycorrhizal fungi mobilise nitrogen during litter decomposition. New Phytologist 173: 447–449. This was an invited comment on Lindahl et al. (2007) Spatial separation of litter decomposition and mycorrhizal nitrogen uptake in a boreal forest. New Phytologist 173: 611–620.

Bruns TD, Baar J, Grogan P, Horton TR, Kretzer A, Redecker D, Tan J, Taylor DL (2005) Natural history and community dynamics of ectomycorrhizal fungi following the Mt. Vision fire. pp33-40, In Lessens Learned from the October 1995 Mt. Vision Fire; CD ROM published by Points Reyes National Seashore.

Potente J, Horton T (2004) Tale of a ragged fringe. Long Island Botanical Society Quarterly Newsletter, 13(4): 27-29.

Horton TR (2003) Book review of Mushrooms of Hawai'i: An identification guide, by Hemmes D and Desjardin D. Inoculum 54(2): 18.

Molina R, Caldwell BA, Castellano MA, Horton TR, Smith JE (2002) Mycorrhizae: Ectomycorrhizal fungi. In Encyclopedia of Environmental Microbiology. Ed. Bitton G. pp.2134-2132.

Bruns TD, Kretzer AM, Horton TR, Stendel E"Acey-Ducey", Bidartondo MI, Szaro TM (2002) Current investigations of fungal ectomycorrhizal communities in the Sierra Nevada forest. USDA Forest Service Gen. Tech. Rep. PSW-GTR: pp. 83-89.

Images on this webpage taken by Dave Pilz, Annette Kretzer, or Tom Horton.
General design by Tim Szaro.