Ryan Thum, Ph.D.

Assistant Professor

224 Lake Michigan Center
740 W. Shoreline Dr.

Muskegon, MI 49441
(616) 331-3989









Areas of Interest:

  • Molecular Ecology
  • Invasion Biology

My general fields of interest encompass evolutionary and molecular ecology, with a specific emphasis on invasive aquatic species. While deeply rooted in basic evolutionary ecology research, my laboratory also puts research into action in tangible ways.  Thus, in addition to publications in peer-reviewed journals, the research leads to policy and management through interactions with regulatory agencies (e.g., Department of Environmental Quality) and into commercial products such as risk assessment tools.  Students graduating with a Master of Science degree from my lab therefore network with collaborators from a variety of public and private sectors, and thus have a variety of career options, such as academia, government, environmental consulting, business, and industry.

The current focus of my laboratory is the evolutionary ecology of invasiveness and herbicide resistance in aquatic plants, with a particular emphasis on hybridization and evolution.  These projects include studies of: the genetic basis of herbicide response, population structure, molecular evolution of candidate genes for herbicide response, and gene expression differences.  There are a wide variety of opportunities for students and post-docs to develop collaborative projects in this area.  Additional opportunities are available for students in other research areas.  Just call or email.

For a brief tour of research and teaching, Click Here to check out the GVSU Center for Scholarly and Creative Excellence short video of my lab. 


  • Ph.D. - Dartmouth College (2004)
  • B.S. - Florida State University (1998)
  • Postdoctoral Fellow - Cornell University (2004-2006)
  • University of Illinois at Urbana-Champaign (2006-2007)


  • Homola, JJ, CR Ruetz, III, SA Kohler, and RA Thum. Weak effects of a microsporidian parasite on mottled sculpin in Michigan streams. Accepted to Canadian Journal of Fisheries and Aquatic Sciences.

  • Borrowman, KR, EPS Sager, and RA Thum. 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 EA, D Grimm, and RA Thum. 2013. Laboratory crosses and genetic analysis of natural populations demonstrate sexual viability of invasive hybrid watermilfoils (Myriophyllum spicatum x M. sibiricum). Aquatic Botany 109: 49-53.

  • LaRue, EA, MP Zuellig, MD Netherland, MA Heilman, and RA Thum. 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 (open access)
  • Allen, MR, Thum, RA, VanDyke, JN, and Cáceres, CE. 2012. Trait sorting in Daphnia colonizing recently-formed lakes. Freshwater Biology 57(9): 1813-1822. 
  • Tavalire, H. F., Bugbee, G., LaRue, E. A., Thum, R. 2012. Hybridization, cryptic diversity, and invasiveness in introduced variable-leaf watermilfoil. Evolutionary Applications 5: 892–900. (open access)
  • Thum, R.A., Heilman, M.A. et al. (8 other authors). 2012. Field and laboratory documentation of reduced fluridone sensitivity by a hybrid watermilfoil biotype (Myriophyllum spicatum x Myriophyllum sibiricum). Journal of Aquatic Plant Management 50: 141-146.
  • Zuellig, M.P. and R. A. Thum. 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.
  • Thum, R.A., A.T. Mercer, and D. Wcisel. 2012. Loopholes in the regulation of invasive species?: Genetic identifications identify the sale of invasive and uncharacterized watermilfoils. Biological Invasions 14: 929-937
  • 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.  In press (January 2012), Journal of Aquatic Plant Management 50: 48-54.
  • Thum, R.A., M. P. Zuellig, M.E. Moody, C. Vossbrinck, and R.L. Johnson. 2011. Molecular markers reconstruct the invasion history of variable leaf watermilfoil (Myriophyllum heterophyllum) and distinguish it from closely related species. Biological Invasions 13: 1687-1709.
  • LaRue, E.A., C.R. Ruetz, III, M.B. Stacey, and R.A. Thum. 2011. Population genetic structure of the invasive round goby in Lake Michigan: implications for natural versus anthropogenic dispersal after introduction. Hydrobiologia 66: 71-82.
  • Allen, M., Thum, R.A., Caceres, C. 2010. Does resource monopolization explain genetic differentiation in Daphnia populations? Molecular Ecology 19:3076-3087.
  • Thum, R.A., and J.T. Lennon. 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.
  • Thum, R.A., and Harrison, R.G. 2009. Deep genetic divergences among morphologically similar and parapatric Skistodiaptomus (Copepoda: Calanoida: Diaptomidae) challenge the hypothesis of Pleistocene speciation. Biological Journal of the Linnean Society 96: 150-165.
  • Thum, R.A., and Derry, A. 2008. Taxonomic implications for diaptomid copepods based on contrasting patterns of mitochondrial DNA sequence divergences in four morphospecies. Hydrobiologia 614: 197-207.
  • Thum, R.A. 2007. Reproductive interactions and the maintenance of parapatry in Skistodiaptomus copepods. Oikos 116: 759-768.
  • Thum, R.A., and Lennon, J.T. 2006. Is hybridization responsible for aggressive growth of non-indigenous water-milfoils? Biological Invasions 8: 1061-1066.
  • Thum, R.A., Lennon, J.T., Connor, J., and A.P. Smagula. 2006. A DNA fingerprinting approach for distinguishing among native and non-native milfoils. Lake and Reservoir Management 22: 1-6.
  • Thum, R.A, and Stemberger, R.S. 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, R.A., Brown, J.M., and McPeek, M.A. 2005. Simultaneous quaternary radiations of three damselfly clades across the holarctic. American Naturalist 165: E78-E107.
  • Thum, R.A. 2004. Using 18S rDNA to resolve diaptomid copepod (Copepoda: Calanoida: Diaptomidae) phylogeny: an example with the North American genera. Hydrobiologia 519: 135-141.
  • James, F.C., C.A. Hess, B.C. Kicklighter, and R.A. Thum. 2001. Ecosystem management and the niche gestalt of the red-cockaded woodpecker in longleaf pine forests. Ecological Applications 11: 854-870.

Invited publications -

  • CABI. Myriophyllum heterophyllum [original text by R.A. Thum and M.P. Zuellig]. Wallingford, UK: CABI (*This is an account of invasive variable leaf water-milfoil for a global invasive species compendium); available at


  • Molecular Ecology (Winter term each year)
  • Independent Research Experience for course credit (by request)


Page last modified February 23, 2014