Thum photo

Ryan Thum, Professor - Ph.D. from Dartmouth College 2002


Office: 313 Plant BioScience Building
Lab: 339 Plant BioScience Building

Office Phone: 406-994-4039
Fax: 406-994-7600

Email Dr. Thum


My general fields of interest encompass evolutionary and molecular ecology, with a specific emphasis on invasive aquatic species. My research is rooted in conceptual evolutionary ecology, but aims to contribute conceptual knowledge and understanding to guide practical decision making and solutions regarding invasive species – one of the world’s most pressing environmental problems. Philosophical questions regarding invasive species are complex, and require the integration of scientific discovery in complex natural systems with discovery and understanding of complex human dimensions such as economics and human behavior. Specific questions that motivate my science include: How do we effectively detect and monitor new invaders? How do we balance effort on preventing new introductions versus reducing the spread and impacts of those that are already established? How do we develop environmentally, economically, and socially sustainable management methods? When, where, why, and how will invasive species evolve resistance to management efforts? And, what are the economic ecological, environmental health consequences of resistance?

Methodologically, projects in my lab utilize field and laboratory studies of aquatic plant growth and management response, evolutionary genetics, and numerical simulation modeling. But projects are not restricted to these techniques alone, and new methods are integrated into the lab through new projects and collaborations that broaden and/or deepen focal areas of inquiry.


Ecology and genetics of invasive aquatic plants.


B.S. Biology, Florida State University (1998)

Ph.D., Ecology and Evolutionary Biology, Dartmouth College (2004)

Postdoctoral Fellow, Cornell University (2004-2006)

Postdoctoral Fellow, University of Illinois at Urbana-Champaign (2006-2007)


Evolution BIOB 420

Genetics BIOB 375



Thum, RA, Parks,S,  McNair, JN, Tyning, P, Hausler, P, Chadderton, L, Tucker, A, Monfils, A. Survival and vegetative regrowth of Eurasian and hybrid watermilfoil following operational treatment with auxinic herbicides in Gun Lake, Michigan, USA. Submitted, Journal of Aquatic Plant Management. 

Taylor LAL, McNair JN, Guastello P, Pashnick J, Thum RA. Heritable variation for vegetative growth rate in ten distinct genotypes of hybrid watermilfoil. In revision, Journal of Aquatic Plant Management.

Parks, S, McNair, JN, Hausler, P, Tyning, P, and Thum, RA. (2016) Divergent responses of cryptic invasive watermilfoils to treatment with auxinic herbicides in a large Michigan Lake. Lake and Reservoir Management 32:366–372.

Moody, ML, Palomino, PS, Weyl, PS, Coetzee, JA, Newman, RM, Liu, X, Xu, X, Harms, N, Thum, RA. (2016) Unraveling the Bieogeographic History of the Eurasian Watermilfoil Invasion in North America. American Journal of Botany 103: 709-718.

Weyl, PS, Thum, RA, Moody, ML, Newman, RM, Coetzee, JA. (2016) Was Myriophyllum spicatum L. (Haloragaceae) recently introduced to South Africa from Eurasia? Aquatic Botany 128: 7-12.

Newton, J, Sepulveda, A, Sylvester, K, Thum, RA. (2016) Potential utility of environmental DNA for early detection of Eurasian watermilfoil (Myriophyllum spicatum). Journal of Aquatic Plant Management 54: 46-49.

Homola, J, Ruetz III, C, Kohler, S, & Thum, RA. (2016) Complex post-glacial recolonization inferred from a sedentary fish: mottled sculpin (Cottus bairdii) in western Michigan, USA rivers. Journal of Fish Biology 89: 2234–2250.

Borrowman, K, Sager, E, Thum, RA. (2015) Growth and developmental performance of the milfoil weevil on distinct lineages of Eurasian watermilfoil and northern x Eurasian hybrid. Journal of Aquatic Plant Management 53: 81-87.

Parks, S, Thum, RA, Pashnick, J, Tyning, P, & Huberty, L. (2014) Incorporating genetic identifications of watermilfoils into aquatic vegetation mapping to inform management decisions. The Michigan Riparian 49: 22-25.

Homola, J, Ruetz III, C, Kohler, S, & Thum, RA. (2014) Weak effects of a microsporidian parasite on mottled sculpin in Michigan streams. Canadian Journal of Fisheries and Aquatic Sciences 71: 795-798.

Borrowman, K, Sager, E, & Thum, RA. (2014) The distribution of biotypes and hybrids of Myriophyllum spicatum and associated Euhrychiopsis lecontei in lakes of Central Ontario. Lake and Reservoir Management 30: 94-104.

LaRue, E. A., Grimm2, D., & Thum, RA. (2013) Invasive hybrid watermilfoils are sexually viable: evidence from laboratory crosses and genetic analysis of natural populations. Aquatic Botany 109: 49-53.

LaRue, E.A, Zuellig, MP, Netherland, MD, Heilman, MA, & Thum, RA. (2013) Hybrid watermilfoil lineages are more invasive and less sensitive to a commonly used herbicide than their exotic parent (Eurasian watermilfoil). Evolutionary Applications 6: 462-471.

Tavalire, HF, Bugbee, GE, LaRue, E, and Thum, RA. (2012) Hybridization and the evolution of invasiveness: Introduced hybrids are more invasive than introduced parental genotypes of variable leaf watermilfoil. Evolutionary Applications 5: 892-900.

Thum, RA, Wcisel, DJ, Zuellig, MP, Heilman, M, Hausler, P, Tyning, P, Huberty, L, Netherland, MD. (2012) Field documentation of decreased herbicide response by a hybrid watermilfoil population. Journal of Aquatic Plant Management 50: 141-146.

Zuellig , MP, Thum, RA. (2012) Multiple introductions of invasive Eurasian watermilfoil and recurrent hybridization with native northern watermilfoil in North America. Journal of Aquatic Plant Management 50: 1-19.

Allen, MR, Thum, RA, VanDyke, JN, and Cáceres, CE. (2012) Trait sorting in Daphnia colonizing man-made lakes. Submitted, Freshwater Biology 57 (9): 1813-1822.

Poovey, A. G., Mudge, C. R., Thum, R., James, C., Getsinger, K. D. (2012) Evaluations of contact aquatic herbicides for controlling two populations of submersed flowering rush.  Journal of Aquatic Plant Management 50: 48-54.

Thum, R., Mercer, A. T., & Wcisel, D. J. (2012). Loopholes in the regulation of invasive species: genetic identifications identify mislabeling of prohibited aquarium plants. Biological Invasions, 14(5), 929-937.

Thum, RA, Zuellig, MP, Moody, M, Johnson, R, Vossbrinck, C. (2011). Molecular markers reconstruct the invasion history of variable leaf watermilfoil (Myriophyllum heterophyllum) and distinguish it from closely related species Biological Invasions 13 (7) 1687-1709

LaRue, E, Stacey, MB, Ruetz III, C, Thum, RA. (2011). Population genetic structure of the round goby in Lake Michigan: implications for dispersal of invasive species Hydrobiologia 663 (1) 71-82

Vossbrinck, C, LaRue, E, Thum, RA, o. a. (2011) Isolation of microsatellite markers for the watermilfoil weevil Euhrychiopsis lecontei. Molecular Ecology Resources

Thum, RA, Zuellig, M. Myriophyllum heterophyllum. In CABI International (Ed.), Compendium of invasive species (

Thum, RA, Lennon, JT. (2010). Comparative ecological niche models predict the invasive spread of variable-leaf milfoil (Myriophyllum heterophyllum) and its potential impact on closely related native species Biological Invasions 12 133-143

Allen, M, Thum, RA, Cáceres, CE. (2010). Does resource monopolization explain genetic differentiation in Daphnia populations? Molecular Ecology 19 (15) 3076-3087

Thum, RA, Harrison, RG. (2009). Deep genetic divergences among morphologically similar and parapatric Skistodiaptomus (Copepoda: Calanoida: Diaptomidae) refute the hypothesis of Pleistocene speciation Biological Journal of the Linnean Society 96 150-165

Thum, RA, Derry, A. (2008). Contrasting patterns of mitochondrial DNA sequence divergences in two morphospecies of diaptomid copepods: taxonomic implications Hydrobiologia 614 197-207

Thum, RA. (2007) Reproductive interactions and the maintenance of parapatry in Skistodiaptomus copepods. Oikos 116: 759-768.

Thum, RA., and Lennon, JT. (2006) Is hybridization responsible for aggressive growth of non-indigenous water-milfoils? Biological Invasions 8: 1061-1066.

Thum, RA, Lennon, JT, Connor, J, and Smagula, AP. (2006) A DNA fingerprinting approach for distinguishing among native and non-native milfoils. Lake and Reservoir Management 22: 1-6.

Thum, RA, and Stemberger, RS. (2006) Pure spatial and spatially-structured environmental variables explain copepod range limits. Canadian Journal of Fisheries and Aquatic Sciences 63: 1397-1404.

Turgeon, J, Stoks, R, Thum, RA, Brown, JM, and McPeek, MA. (2005) Simultaneous quaternary radiations of three damselfly clades across the holarctic. American Naturalist 165: E78-E107.

Thum, RA. (2004) Using 18S rDNA to resolve diaptomid copepod (Copepoda: Calanoida: Diaptomidae) phylogeny: an example with the North American genera. Hydrobiologia 519: 135-141.

James, FC, Hess, CA, Kicklighter,BC and Thum, RA. (2001) Ecosystem management and the niche gestalt of the red-cockaded woodpecker in longleaf pine forests. Ecological Applications 11: 854-870.