Colonization history of the western corn rootworm Diabrotica virgifera virgifera in North America: insights from random forest ABC using microsatellite data

Authors: LOMBAERT, ERIC - Institut National De La Recherche Agronomique (INRA); CIOSI, MARC - Institut National De La Recherche Agronomique (INRA); MILLER, NICHOLAS - Illinois Institute Of Technology; Sappington, Thomas; BLIN, AURELIE - Institut National De La Recherche Agronomique (INRA); GUILLEMAUD, THOMAS - Institut National De La Recherche Agronomique (INRA)

Submitted to: Biological Invasions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2017
Publication Date: 3/1/2018
Citation: Lombaert, E., Ciosi, M., Miller, N.J., Sappington, T.W., Blin, A., Guillemaud, T. 2018. Colonization history of the western corn rootworm Diabrotica virgifera virgifera in North America: insights from random forest ABC using microsatellite data. Biological Invasions. 20(3):665-677. https://doi.org/10.1007/s10530-017-1566-2.
DOI: https://doi.org/10.1007/s10530-017-1566-2

Interpretive Summary: The western corn rootworm is the worst pest of corn in North America and has invaded most of Europe as well. For many years after it was first described to science in 1868, it was barely noticed, but it began to attack corn in the central Great Plains in the first half of the 20th century. Nevertheless, it remained only a regional pest until the late 1940s when it began a rapid invasion of the U.S. Corn Belt and the eastern half of the U.S. The nature of its invasiveness is an important question globally, and yet we know little about how it came to the U.S. in the first place. There is evidence that it arose in Mexico or Central America and shifted host plants to attack corn as this plant was domesticated in ancient times and followed corn northward as this plant was adopted by Native Americans. But it is also possible it originated in the Great Plains and spread to Mexico. In this study, profiles of DNA markers from rootworms collected throughout North America are used in cutting-edge analyses to gain insight on the species' origin. The results show that it arose in Mexico, but surprisingly, it did not spread north until long after corn was being grown throughout North America. This information will be of interest to entomologists, corn breeders, and regulators in the U.S., Canada, and Europe who are interested in managing the invasion and spread of this pest.

Technical Abstract: First described in Kansas, USA, the western corn rootworm, Diabrotica virgifera virgifera, is one of the worst pests of maize. The species is generally thought to be of Mexican origin, which incidentally followed the expansion of maize into North America thousands of years ago. However, this hypothesis has never been investigated formally. In this study, the genetic variability of samples collected throughout North America was analyzed at 13 microsatellite marker loci to explore precisely the population genetic structure and colonization history of D. v. virgifera. In particular, we used up-to-date Approximate Bayesian Computation methods based on Random Forest algorithms to test a Mexican versus a central-USA origin of the species, and to compare various possible timings of colonization. This analysis provided strong evidence that the origin of D. v. virgifera was Mexico, or even further south. Surprisingly, we also found that the expansion of the species north of its origin was recent – it started probably less than 1000 years ago – thus indicating it was not directly associated with the history of maize expansion out of Mexico, which is a far more ancient event.