Identifying the geographic origins of invasive Megathyrsus maximus in the United States using molecular data

Authors: Gaskin, John; Goolsby, John; BON, MARIE-CLAUDE - European Biological Control Laboratory (EBCL); CALATAYUD, PAUL-ANDRE - International Centre Of Insect Physiology And Ecology; CRISTOFARO, MASSIMO - Biotechnology And Biological Control Agency

Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2022
Publication Date: 5/19/2022
Citation: Gaskin, J.F., Goolsby, J., Bon, M., Calatayud, P., Cristofaro, M. 2022. Identifying the geographic origins of invasive Megathyrsus maximus in the United States using molecular data. Invasive Plant Science and Management. 15(2):67-71. https://doi.org/10.1017/inp.2022.7.
DOI: https://doi.org/10.1017/inp.2022.7

Interpretive Summary: Guineagrass is non-native in the southern USA and the neotropics, with a tall form of the species utilized as a forage grass and a short form considered invasive. Biological control researchers are challenged to find an agent that will attack the short form yet leave the tall form undisturbed. We conducted molecular analyses on Guineagrass samples from its native range in Africa and compared them to USA short form samples to help determine the origins of invasion. We found eight distinct genotypes in 34 samples from Texas and Florida, USA. Highest genetic similarity of invasive samples was with plants from South Africa, while highest matches for the desirable tall form were from Kenya, Uganda, Ivory Coast and Zambia. Additional exploration is needed at the genetic match site in South Africa to discover and evaluate potential biological control agents for invasive Guineagrass.

Technical Abstract: Guineagrass is non-native in the southern USA and the neotropics, with a tall form of the species utilized as a forage grass and a short form considered invasive. Biological control researchers are challenged to find an agent that will attack the short form yet leave the tall form undisturbed. We conducted molecular analyses on 155 Guineagrass samples from its native range in Africa and compared them to USA short form samples to help determine the origins of invasion. We found eight distinct genotypes in 34 samples from Texas and Florida, USA. Highest genetic similarity of invasive samples was with plants from South Africa, while highest matches for the desirable tall form were from Kenya, Uganda, Ivory Coast and Zambia. Ongoing biological control agent exploration and research has found agents from Kenya that are from a Guineagrass genotype not well-matched to the invasive short form, leading to lack of rearing success and two eriophyioid mite agents from the genetic match site in South Africa have been evaluated but are not sufficiently host-specific as they develop on both the short and tall forms. Additional exploration is needed at the genetic match site in South Africa to discover and evaluate potential biological control agents for invasive Guineagrass.