Amaranthus tuberculatus can adapt to agricultural systems in North America
Amaranthus tuberculatus (Amaranthaceae - EPPO A2 List) is an annual dioecious non-native species to the EPPO region with transient and established occurrences known from a number of EPPO countries. The species grows mainly in ruderal sites and along riverbanks, and to a lesser extent in crop fields (EPPO RS 2020/107). The species is native to the Midwestern US where it began infesting agricultural fields in the 20th century within the central portion of its range. In the USA, two common garden experiments were set-up to test if vegetative growth and reproductive traits of A. tuberculatus from the region with the highest level of agricultural infestation provide differential fitness benefits in agricultural environments. Seed was collected from across the species native range, representing regions with varying degrees of infestation. Seeds from different populations were planted together in soybean plots. A 2010 common garden experiment was conducted within its agriculturally weedy range (in Missouri), and a 2011 common garden experiment was conducted outside of this range (in Ohio). Days to flowering and flowering plant height, mature plant size data (height, number of branches, and length of the longest branch), and above-ground biomass were measured to estimate relative fitness. In both common garden locations, plants from regions where A. tuberculatus occurs as an agricultural weed—including those from the heavily infested Mississippi Valley region (Iowa, Illinois, and Missouri) and the less severely infested Plains region (Nebraska, Kansas, and Oklahoma)—had higher relative performance in almost all fitness-related measures than plants from the Northeast region (Ohio, Michigan, and Ontario), which had little to no agriculturally weedy A. tuberculatus.
Waselkov KE, Regenold ND, Lum RC, Olsen KM (2020) Agricultural adaptation in the native North American weed waterhemp, Amaranthus tuberculatus (Amaranthaceae). PLoS ONE 19(9) e0238861. https://doi.org/10.1371/journal.pone.0238861