Figure 1.

Types of sites identified in this study. ‘Historical’ sites are those where the occurrence of Heracleum mantegazzianum was reported up to 2007. The species still occurs at some of these sites (‘Persisting’), whereas it has disappeared from others, as inferred from its absence during systematic revisiting in the period 2008–2009 (‘Disappeared’). This recent research yielded information on new sites in which the species had not been recorded in the past (‘New’). ‘Current’ sites therefore represent the actual distribution confirmed by the recent survey, while ‘Cumulative’ distribution refers to all sites, both ‘Historical’ and ‘New’, from which the species has ever been reported. Finally, the ‘Real’ distribution takes into account that there are ‘Undetected’ sites that escaped recording both in historical data up to 2007, and in the recent sampling in 2008–2009. The numbers in brackets show the representation of individual sites for H. mantegazzianum.