Amaranthus palmeri, a second record for Africa and notes on A. sonoriensis nom. nov.
Background: Amaranthus is a critical genus from a taxonomic point of view because of its high phenotypic variability, which has led to nomenclatural disorder, misapplication of names, and erroneous species identification. As a whole, floristic and taxonomic studies on this genus are still incomplete. Objectives: The main objective was to record the North American species Amaranthus palmeri in Tunisia for the first time and to point out a second occurrence for Africa. At the same time, we highlight some nomenclatural confusion concerning the name A. palmeri var. glomeratus which appears to be untypified and which should be treated at species rank. Method: The work is based on field surveys, analysis of relevant literature and examination of specimens preserved in the herbaria GH, FI, HFLA, K, MICH, NEBC, NY, MO, P, RO, US, and the Herbarium of Bizerta University. Results: A population of Amaranthus palmeri was discovered in Bizerta Province, representing the first record for the national flora. This record also represents the second record for Africa. Morphological characters, as well as ecological data are provided. Nomenclatural notes are provided for A. palmeri var. glomeratus (lectotype at GH, here designated; isolectotypes at MICH and US), and a new name (A. sonoriensis) is proposed. Conclusion: Amaranthus palmeri is an alien species in Tunisia, growing along roadsides and in public gardens. Future monitoring of the populations found will be necessary to verify possible naturalisation and spreading of A. palmeri in Tunisia. If this happens, actions for eradication of the plants will be necessary.