8. Setaria verticilliformis Dum. [syn.: S. ambigua (Guss.) Guss., S. decipiens C. Schimp. ex Aschers., S. verticillata subsp. ambigua (Guss.) K. Richt., S. verticillata var. ambigua (Guss.) Parl.] (warm-temp. areas of the Old World) – First discovered in two maize fields in the surroundings of Aalter around 1990 (Lambinon & al. 1993). A subsequent herbarium revision yielded no earlier records (Hoste 2006). Since its discovery it is an increasing alien but it is nearly exclusively found in maize fields, especially in Flanders (Hoste & Verloove 2001). Setaria verticilliformis often grows along with S. verticillata but it is much less common: in an area between Brugge and Gent it was recorded in 17% of 320 square kilometers that were investigated in 1999-2000 while S. verticillata was present in 83% (Hoste 2006). This might be due to its less effective way of dispersal (i.e. the antrorse scabridity of the bristles).
In Belgium the distinction of this species and Setaria verticillata is always straightforward and no plants with intermediate characters have been found. Setaria verticilliformis therefore apparently deserves specific rank (see also Pensiero 1999, Rominger 2003, Morrone & al. 2014, Euro+Med Plantbase). Molecular data, however, suggest its inclusion in Setaria verticillata (Layton & Kellogg 2014). Setaria verticilliformis is still considered to be a putative hybrid between S. verticillata and S. viridis by some authors (see for instance Ryves & al. 1996). This seems rather unlikely.
The Australian Setaria dielsii R.A.W. Herrmann, formerly observed as a wool alien in the Vesdre valley, is considered conspecific by Morrone & al. (2014).
The exact origin of Setaria verticilliformis is uncertain. It was described from Luxembourg and is supposedly native in western Europe but it has not been collected in Belgium prior to 1990.
Selected literature:
Hoste I. (2006) Setaria verticillata. In: Van Landuyt W., Hoste I., Vanhecke L., Van den Bremt P., Vercruysse W. & De Beer D., Atlas van de flora van Vlaanderen en het Brussels gewest. Instituut voor Natuur- en Bosonderzoek, Nationale Plantentuin van België en Flo.Wer: 827.
Hoste I. & Verloove F. (2001) De opgang van C4-grassen (Poaceae-Paniceae) in de snel evoluerende onkruidvegetaties in maïsakkers tussen Brugge en Gent (Vlaanderen, België). Dumortiera 78: 2-11.
Lambinon J., Heyneman G. & Goetghebeur P. (1993) Découverte en Flandre de Setaria verticillata (L.) P. Beauv. var. ambigua (Guss.) Parl., graminée nouvelle pour la flore belge. Soc. Ech. Pl. Vasc. Eur. Bass. Médit., Bull. 24: 85-86.
Layton D.J. & Kellogg E.A. (2014) Morphological, phylogenetic, and ecological diversity of the new model species Setaria viridis (Poaceae: Paniceae) and its close relatives. Am. J. Bot. 101(3): 539-557.
Pensiero J.F. (1999) Las especies sudamericanas del género Setaria (Poaceae, Paniceae). Darwiniana 37(1-2): 37-151.
Rominger J.M. (2003) Setaria. In: Barkworth M.E. & al. (eds.), Flora of North America north of Mexico, vol. 25: 539-558. Oxford University Press, New York-Oxford.
Ryves T.B., Clement E.J. & Foster M.C. (1996) Alien grasses of the British Isles. BSBI, London: XX + 181 p.
Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.