Genetic analysis of invasive populations of Ventenata dubia (Poaceae): an assessment of propagule pressure and pattern of range expansion in the USA

Authors: PERVUKHINA-SMITH, INNA - Boise State University; SFORZA, RENE - European Biological Control Laboratory (EBCL); CRISTOFARO, MASSIMO - Bbca-Onlus, Italy; SMITH, JAMES - Boise State University; NOVAK, STEPHEN - Boise State University

Submitted to: Biological Invasions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2020
Publication Date: 8/19/2020
Citation: Pervukhina-Smith, I., Sforza, R., Cristofaro, M., Smith, J.F., Novak, S.J. 2020. Genetic analysis of invasive populations of Ventenata dubia (Poaceae): an assessment of propagule pressure and pattern of range expansion in the USA. Biological Invasions. 22:3575–3592. https://doi.org/10.1007/s10530-020-02341-2.
DOI: https://doi.org/10.1007/s10530-020-02341-2

Interpretive Summary: Invasive plants occupy over 40 million hectares in the United States (U.S.) and spread at a rapid rate. Ventenata dubia (common names North Africa grass or wiregrass, Aveneae), is a recently introduced invasive annual grass with the potential to cause much ecological and economic damage in the Northwest U.S. V. dubia is now considered a high landscape-level stressor., and is beginning to receive a attention due to its rate of spread and difficulty in its control. Currently it is found throughout the U.S. (WA, OR, CA, ID, UT, MT, WY, WI, NY, ME) and Canada (BC, AB, ON, QC, NB). . V. dubia is similar in appearance to Bromus tectorum (cheatgrass) as both are annuals, similar in height and have open panicles. Molecular analysis can reveal the genetic signatures of propagule pressure, the amount and distribution of genetic diversity within and among populations, and the occurrence and consequences of post-introduction events. No previous studies have assessed the genetic diversity, introduction dynamics, and pattern of spread of V. dubia in its invasive range, and the species provides an excellent opportunity to obtain insights into the mechanisms of biological invasion and an initial assessment of the population genetic consequences associated with invasion. In this study we analyzed 51 invasive populations of V. dubia coupled with historical records. Our molecular data suggested: 1) a moderate propagule pressure from multiple introductions, followed by local or regional range expansion in the western US, 2) a minimum of nine genotypes cross eight western US States, with a single type identified as the most common. Lastly, it showed that despite multiple introductions, invasive populations exhibit low levels of genetic admixture, low levels of genetic diversity within populations and high genetic differentiation among populations. Results of this genetic analysis indicated that V. dubia was introduced multiple times into the western US. This information will be used by scientists and industry.

Technical Abstract: Molecular markers prove to be an invaluable tool in assessing the introduction dynamics, pattern of range expansion, and genetic diversity of an invasive species. Ventenata dubia (Leers) Coss. (Aveneae; ventenata) is a diploid, primarily self-pollinating, annual grass native to Eurasia and Northern Africa. The grass has a detailed herbarium collection history in the western United States (US) since its discovery in eastern Washington in 1952. Genetic analysis of 51 invasive populations (1,636 individuals) of V. dubia coupled with historical records suggest moderate propagule pressure from multiple introductions, followed by local or regional range expansion. Enzyme electrophoresis detected nine multilocus genotypes (MLGs) across eight western US States. A single MLG, referred to as the most common genotype (MCG), was detected in 37 of 51 (72.5%) invasive populations across all states. The other eight MLGs were generally found in fewer populations, with limited geographic distributions. Despite multiple introductions, invasive populations exhibit low levels of genetic admixture, low levels of genetic diversity within populations (A = 1.03, %P = 2.94, Hexp = 0.007) and high genetic differentiation among populations (GST = 0.864). The apparent reduced evolutionary potential of most V. dubia populations did not preclude the initial establishment and rapid spread of this species across its new range in the western US.