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United States Department of Agriculture

Agricultural Research Service

John F Gaskin

Supervisory Research Biologist


John Gaskin.John F. Gaskin

PMRU Research Leader and Research Biologist

ASRU Acting Research Leader  


Phone: 406.433.9444

Fax: 406.433.5038


Education • Current Research • Research Experience • Related Web Pages • Publications •



Additional Pages: Research Projects,*Publications*

*Taken from the Agricultural Research Information System (ARIS) database.




B.S. Biology 1996 University of California, Santa Cruz, CA
Ph. D. Evolutionary & Population Biology 2002 Washington University in St. Louis & Missouri Botanical Garden, MO





The focus of my research is the systematics and population structure of invasive plants, particularly whitetop or hoarycress (Lepidium draba, formerly Cardaria draba) and saltcedar (Tamarix spp.) Both of these invasives are present in Montana and throughout the western U.S. Saltcedar typically dominates riparian areas and whitetop is considered a pest plant in fields, rangelands and natural areas. The specific goals of this research are to find out which genotypes of these exotic plants are invading, where the genotypes originated from in Eurasia, which native and exotic species they are most closely related to, and where the invasive genotypes are distributed in the U.S. This information will be used to insure that all of the genetic diversity of these invasions will be present in tests of current and proposed biological control agents, and that all native plants closely related to the invasion will be included in host-specificity tests.





Prior to joining the USDA-Agricultural Research Service in 2002, my dissertation at Washington University in St. Louis focused on the phylogeography of invasive Tamarix. I have done revision work on South American Smilax, and molecular systematic work in the families Campanulaceae and Tamaricaceae.





MBG: Missouri Exotic Pest Plants




Please note: The most recent publications by this scientist may not yet be listed here. Please check the ARIS "Publications" page for possible new titles.

  • Brullo, C., Brullo, S., Gaskin, J.F., Giusso Del Galdo, G., Hrusa, G., Salmeri, C. 2015. A new species of Kali (Salsoloideae, Chenopodiaceae) from Sicily, supported by molecular analysis. Phytotaxa. DOI: 10.11646/phytotaxa.201.4.2. 21(4):256-277.
  • Mayonde, G., Cron, G.V., Gaskin, J.F., Byrne, M.J. 2015. Evidence of Tamarix hybrids in South Africa, as inferred by nuclear ITS and plastid trnS-trnG DNA sequences. South African Journal of Botany. 96:122-131. (PDF)
  • Caesar, A.J., Lartey, R.T., Caesar, T., Gaskin, J.F. 2014. First report of Rhizoctonia spp. causing a root rot of the invasive rangeland weed Lepidium draba in North America. Plant Disease Notes. 98(9):1278. DOI: 10.1094/PDIS-03-14-0300-PDN.
  • Caesar, T., Stevens, W.B., Sainju, U.M., Caesar, A.J., West, M.S., Gaskin, J.F. 2014. Soil-aggregating bacterial community as affected by irrigation, tillage, and cropping system in the Northern Great Plains. Soil Science. 179(1):11-20. (PDF)
  • Stohlgren, T., Szalanski, A., Gaskin, J.F., Young, N., West, A., Jamevich, C., Tripodi, A. 2014. From hybrid swarms to swarms of hybrids. Diversity and Distributions. 2(8):311-318. (PDF)
  • Villar, J.L., Alonso, M., Gaskin, J.F., Juan, A., Crespo, M.B. 2014. Proposal to conserve Tamarix ramosissima against T. pentandra Tamaricaceae). Taxon. 63(5):1140-1142. (PDF)
  • Williams, W., Friedman, J., Gaskin, J.F., Norton, A. 2014. Hybridization of an invasive shrub affects tolerance and resistance to defoliation by a biological control agent. Evolutionary Applications. 7(3):381-393. (PDF)
  • Bean, D., Kazmer, D.J., Gardner, K., Thompson, D., Reynolds, B., Keller, J.C., Gaskin, J.F. 2013. Molecular genetic and hybridization studies of Diorhabda spp. released for biological control of tamarix. Journal of Invasive Plant Science and Management. 6(1): 1-15. (PDF; 733 KB)
  • Caesar, T., Espeland, E.K., Caesar, A.J., Sainju, U.M., Lartey, R.T., Gaskin, J.F. 2013. Effects of agaricus lilaceps fairy rings on soil aggregation and microbial
    community structure in relation to growth stimulation of western wheatgrass (pascopyrum smithii) in Eastern Montana rangeland. Microbial Ecology. 66(1): 120-131. (PDF)
  • Gaskin, J.F., Schwarzlaender, M., Grevstad, F., Haverhals, M., Bourchier, R., Miller, T. 2014. Extreme differences in population structure and genetic diversity for three invasive congeners: knotweeds in western North America. Biological Invasions. 16(10):2127-2136. DOI: 10.1007/s10530-014-0652-y.  (PDF
  • Gaskin, J.F., Schwartzlander, M., Hinz, H., Williams III, L.H., Gerber, E., Rector, B.G., Zhang, D. 2013. Genetic identity and diversity of perennial pepperweed (Lepidium latifolium) in its native and invaded ranges. Journal of Invasive Plant Science and Management. 6(2):268-280. (PDF)
  • Gaskin, J.F., Schwarzlaender, M., Kinter, L., Smith, J., Novak, S. 2013. Propagule pressure, genetic structure, and geographic origins of Chondrilla juncea (Asteraceae): An apomictic invader on three continents. American Journal of Botany. 100(9):1871-1882. (PDF)
  • Rector, B.G., Ashley, M.C., Gaskin, J.F., Longland, W.S. 2013. Use of wheat SSRs to assess genetic diversity in medusahead (Taenintherum caput-medusae). Invasive Plant Science and Management. 6:352-361.
  • Gaskin, J.F. 2012. Tamaricaceae. In: Baldwin, B.G., Goldman, D.H., Keil, DJ, Patterson, R., Rosatti, T.J., Wilken, Dieter, D.H., editors. The Jepson Manual: Vascular Plants of California, Second Edition. Berkeley, CA: University of California Press. pp. 1259-1261.
  • Gaskin, J. F., Adam S. Birken and David J. Cooper. 2012. Levels of novel hybridization in the saltcedar invasion compared over seven decades. Biological Invasions. 14(3): 693-699. (PDF; 315 KB)
  • Gaskin, J.F., Schwarzlaender, M., Williams, L., Gerber, E., Hinz, H. 2012. Minimal genetic diversity in the facultatively outcrossing perennial pepperweed (Lepidium latifolium) invasion. Biological Invasions. 14:1797-1807. (PDF; 406 KB)
  • Gaskin, J.F., Bon, M.C., Cock, M.J.W., Cristofaro, M., De Biase, A., De Clerck-Floate, R., Ellison, C.A., Hinz, H., Hufbauer, R., Julien, M., and Sforza, R. 2011. Applying molecular-based approaches to classical biological control of weeds. Biological Control. 58:1-21.  (PDF; 323 KB)  
  • Szucs, M., Swarzlander, M., Gaskin, J.F. 2011. Reevaluating establishment and potential hybridization of different biotypes of the biological control agent Longitarsus jacobaeae using molecular tools. Biological Control. 58:44-52. (PDF; 539 KB)
  • Wheeler, G.S., Taylor, G.S., Gaskin, J.F., Purcell, M. 2011. Ecology and management of Australian pine (Casuarina spp.), an invader of coastal Florida, USA. Journal of Coastal Research. 27(3):485-492. (PDF; 324 KB)
  • Al-Shehbaz, I., Gaskin, J.F. 2010. Lepidium. In: Boufford, D., Freeman, C., Gandhi, K., Hill, M., Kiger, R., Poole, J., Schmidt, H., Shultz, L., Strother, J. and Zarucchi, J., editors. Flora of North America. New York, New York, Oxford University Press, Inc. Vol. 7. p. 570-595. (PDF; 4110 KB
  • Caesar, T., Lenssen, A.W., Caesar, A.J., Sainju, U.M., Gaskin, J.F. 2010. Effects of tillage on microbial populations associated to soil aggregates under dryland spring wheat system. European Journal of Soil Biology. 46:119-127.  (PDF; 409 KB)
  • Shi, X. Wang, J.C. Zhang, D.Y. Gaskin, J.F. Pan, B.R. 2010. Pollination ecology of the rare desert species Eremosparton songoricum (Fabaceae). Australian Journal of Botany. 58(1): 35-41. (PDF; 559 KB)
  • Ayres, D., Ryan, F.J., Grotkopp, E., Bailey, J., and Gaskin, J. 2009. Tumbleweed (Salsola) species and speciation in California. Biological Invasions. 11:1175-1187. (PDF; 378 KB)
  • Gaskin, J.F. and D.J. Kazmer. 2009. Introgression between saltcedars (Tamarix chinensis and T. ramosissima) in the USA invasion. Biological Invasions. 11:1121-1130. (PDF; 511 KB)
  • Gaskin, J.F., Wheeler, G.S., Purcell, M., Taylor, G. 2009. Molecular evidence of hybridization in Florida's sheoak (Casuarina spp.) invasion. Molecular Ecology. 18(15):3216-3226. (PDF; 563 KB)
  • Shi, W., Pan, B., Gaskin, J.F., Kang, X. 2009. Morphological Variation and Chromosome Studies of Calligonum mongolicum and C. pumilum (Polygonaceae). Nordic Journal of Botany. 27(2):81-85. (PDF: 170 KB)
  • Caesar, T., Busscher, W.J., Novak, J.M., Gaskin, J.F., Kim, Y. 2008. Effects of Polyacrylamide and Organic Matter on Microbes associated to Soil Aggregation of Norfolk Loamy Sand. Applied Soil Ecology. 40:240-249. (PDF; 1238 KB)
  • Caesar, T., Caesar, A.J., Gaskin, J.F., Sainju, U.M., Stevens, W.B. 2008. Ecology and function of culturable microbes in soil aggregation. In: Tian-Xiao Liu, editor. Soil Ecology Research Developments. Hauppauge, NY:2007 Science Publishers, Inc. p. 121-138.
  • Friedman, J.M., J.E. Rolle, J.F. Gaskin, A.E. Pepper, and J.R. Manhart. 2008. Latitudinal variation in cold hardiness in introduced Tamarix and native Populus. Evolutionary Applications. 1:598-607. (PDF: 203 KB)
  • Hrusa, G.F. and J.F. Gaskin. 2008. The Salsola tragus Complex in California (Chenopodiaceae): Characterization and Status of Salsola australis and the Autochthonous Allopolyploid Salsola ryanii Sp. Nov. Madrono. 55:113-131. (PDF: 4295 KB)
  • Natale, E.S., J. Gaskin, S.M. Zalba, M. Ceballos and H.E. Reinoso. 2008. Especies del genero Tamarix (Tamaricaceae) invadiendo ambientes naturales y seminaturales en Argentina. Bol. Soc. Argent. Bot 43:1-9.
  • Ward, S.M., J.F. Gaskin, and L.M. Wilson. 2008. Ecological Genetics of Plant Invasion: What Do We Know? Invasive Plant Science and Management 1:98-109. (Invited Review in Inaugural Issue.) (PDF: 202 KB)
  • Caesar, T., Caesar, A.J., Gaskin, J.F., and Sainju, U.M., Busscher, W.J. 2007. Taxonomic diversity of predominant culturable bacteria associated with microaggregates from two different agroecosystems and their ability to aggregate soil in vitro. Applied Soil Ecology. 36(1):10-21. (PDF; 535 KB)
  • Gaskin, J.F. 2007. Tamaricaceae. In: Flora of China. Volume 13. University of California Press-Cooperative Extension. 13:58-69. (PDF; 143 KB)
  • Gaskin, J.F., and Wilson, L.M. 2007. Phylogenetic relationships among native and naturalized hieracium (asteraceae) in Canada and the United States based on plastid DNA sequences. Systematic Botany. 32(2):478-485. (PDF; 708 KB)
  • Sword, G.A., Senior, L., Gaskin, J.F., Joern, A. 2007. Double trouble for grasshopper molecular systematics: intra-individual heterogeneity of both mitochondrial 12S-valine- 16S and nuclear internal transcribed spacer ribosomal DNA sequences in Hesperotettix viridis (Orthoptera: Acrididae). Systematic Entomology. 32(3):420-428. (PDF; 239 KB)
  • Whitcraft, C.R., Talley, D.M., Crooks, J.A., Boland, J., and Gaskin, J.F. 2007. Invasion of tamarisk (Tamarix spp.) in a southern California salt marsh. Biological Invasions. 9:875-879. (PDF; 168 KB)
  • Gaskin, J.F. 2006. Clonal structure of invasive hoary cress (Lepidium draba) infestations. Weed Science 54:428-434. (PDF; 197 KB)
  • Gaskin, J.F., Kazmer, D.J. 2006. Comparison of ornamental and invasive saltcedar in the USA northern Great Plains using chloroplast and nuclear DNA sequence markers. Wetlands. 26(4):939-950. (PDF; 545 KB)  
  • Gaskin, J.F., A.E. Pepper, and J.M. Manhart. 2006. Isolation and characterization of ten polymorphic microsatellites in saltcedars (Tamarixchinensis and T. ramosissima). Molecular Ecology Notes 6:1147-1149. (PDF; 74 KB)
  • Gaskin, J.F., Ryan, F.J., Hrusa, G.F. and Londo, J.P. 2006. Genotype diversity of Salsola tragus and potential origins of a previously unidentified invasive Salsola from California and Arizona. Madro?o 53:246-253.
  • Qiner, Y., Gaskin, J.F. 2006. Tamaricaeceae in Flora of China. Flora of China. 13:58-69. (PDF; 142 KB)
  • Zhang, D., Zhang, Y., Gaskin, J.F., and Chen, Z. 2006. Systematic position of Myrtama Ovcz. and Kinz. based on mophological and nr DNA ITS sequence evidence. Chinese Science Bulletin. 51:117-123. (PDF; 855 KB)
  • Bon, M-C, C. Hurard, J. Gaskin, and A-M Risterucci. 2005. Polymorphic microsatellite markers in polyploid Lepidium draba L. subsp. draba (Brassicaceae) and cross-species amplification in closely related taxa. Molecular Ecology Primer Notes 5:68-70. (PDF; 76 KB)
  • Gaskin, J.F. and P.E. Berry. 2005. Smilacaceae in Flora of the Venezuelan Guayana, J.A.Steyermark, P.E. Berry, K. Yatskievych and B.K. Holst (eds.). Missouri Botanical Garden Press, St. Louis, USA. Pp. 184-193.
  • Gaskin, J.F. and P.B. Shafroth. 2005. Hybridization of Tamarix ramosissima and T. chinensis (saltcedars) with T. aphylla (athel) (family Tamaricaceae) in the southwestern USA determined from DNA sequence data. Madro?o 52:1-10.
  • Gaskin, J.F., D-Y. Zhang, and M-C. Bon. 2005. Invasion of Lepidium draba (Brassicaceae) in the western United States: distributions and origins of chloroplast DNA haplotypes. Molecular Ecology 14:2331-2341. (PDF; 339 KB)
  • Shulkina, T., J. Gaskin, and W. Eddie. 2003. Morphological studies toward an improved classification of Campanulaceae s. str. Ann. Missouri Bot. Gard. 90:576-591.
  • Eddie, W.M.M.,T. Shulkina, J. Gaskin, R.C. Haberle, and R.K. Jansen. 2003. Phylogeny of Campanulaceae s. str. inferred from ITS sequences of nuclear ribosomal DNA. Ann. Missouri Bot. Gard. 90:554-575.
  • Schaal, B.A., J.F. Gaskin, and A.L. Caicedo. 2003. Phylogeography, haplotype trees, and invasive plant species. J. Heredity 94 (3):197-204.
  • Gaskin, J.F. 2003. Molecular systematics and the control of invasive plants: a case study ofTamarix (Tamaricaceae). Ann. Missouri Bot. Gard. 90:109-118.
  • Gaskin, J.F. and B.A. Schaal. 2003. Molecular phylogenetic investigation of invasive Tamarix in the U.S.A. Syst. Bot. 28(1):86-95. (PDF: 2134 KB)
  • Gaskin, J.F. and B.A. Schaal. 2002. HybridTamarix widespread in U.S. invasion and undetected in native Asian range. Proc. Natl. Acad. Sci. USA 99:11256-11259.
  • Gaskin, J.F. 2002. Tamaricaceae in The Families and Genera of Vascular Plants V. K. Kubitzki and C. Bayer (eds). Springer-Verlag, Berlin. Pp. 363-368. 

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Last Modified: 5/17/2017
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