Bidens connatus Muhl. ex Willd., Sp. Pl.

Verloove, Filip & Ardenghi, Nicola M. G., 2015, New distributional records of non-native vascular plants in northern Italy, Natural History Sciences 2 (1), pp. 5-14 : 6

Bidens connatus Muhl. ex Willd., Sp. Pl. , ed. 4 [Willdenow], 3 (3): 1718 (-1719). 1803. [ Fig. 1 ] ( Asteraceae )

Naturalized neophyte new to the flora of Piemonte ( Conti et al., 2005; Celesti-Grapow et al., 2009a; Banfi & Galasso, 2010).

ITALY. Piemonte. Prov. Alessandria: Villanova Mon- ferrato, W of motorway E25 , rice fields, 12.09.2014, F. Verloove 11101 ( BR) .

Bidens connatus is originally native in North America but known as a more or less widely naturalized xenophyte in Europe (e.g. Schumacher, 1941; Debray, 1963). In Ita- ly it was known so far from Lombardia, Emilia-Romagna, Friuli-Venezia Giulia, Marche and Veneto, either as a casual, naturalized or invasive alien ( Celesti-Grapow et al., 2009a; Ardenghi, 2015).

In fact, its genuine distribution and degree of naturali- zation should be critically reassessed, the species being much reminiscent of native B. tripartitus L. It is best dis- tinguished from the latter by leaves usually undivided and cypselae 4-angled (not flattened) with usually tuberculate faces ( Strother & Weedon, 2006).

In September 2014 Bidens connatus was recorded on several occasions. In addition to the locality cited above, it was also seen in Valenza, Bastida Pancarana, Boretto, Ficarolo, Mezzano, Piacenza, Ravalle, San Rocco al Porto and Viadana (all along river Po) and in Serravalle Scrivia (along river Scrivia). It is obviously much more widespread, firmly established but widely overlooked.

It should be recalled that according to Art. 62.2(a) of the International Code of Nomenclature ( McNeill et al., 2012), Bidens should be treated as a compound, “ Bi -dens ”, the last word (dens, dentis) being male; then the specific epithet should be “ connatus ” instead of “ connata ” (see also next species). Even though initially recommended by the Report of the Committee for Spermatophyta (Brum- mitt, 2000), the proposal to conserve the name Bidens with a conserved gender ( Harriman, 1998), was finally not upheld (McNeill et al., 2006, App. III) (Banfi & Ga- lasso, 2010).

Figures

Fig. 1 - Bidens connatus, Bastida Pancarana (PV), September 2014 (Photo: N.Ardenghi).