Virial parameter of the ¹²CO (1–0) MCs that have at least one ¹³CO (1–0) associated MC, with the virial parameter of the associated ¹³CO (1–0) MC(s). Only the sub-sample of MCs with a valid determination of the virial parameter (flag1 = 0 in Table A.1) are plotted. Dotted vertical lines connect the virial parameters of the ¹³CO MCs associated with the same single ¹²CO MC. The solid straight line indicates the equivalence of the two parameters.