Dear Alfredo'

Kindly see the following Article and relevant example given in ICN:

• 11.5 When, for any taxon of the rank of family or below, a choice is possible between legitimate names of equal priority in the corresponding rank, or between available final epithets of names of equal priority in the corresponding rank, the first such choice to be effectively published (Art. 29-31) establishes the priority of the chosen name, and of any legitimate combination with the same type and final epithet at that rank, over the other competing name(s) (but see Art. 11.6; see also Rec. 42A.2).

o Ex.21. Brown (in Tuckey, Narr. Exped. Zaire: 484. 1818) was the first to unite Waltheria americana L. (1753) and W. indica L. (1753). He adopted the name W. indica for the combined species, and this name is accordingly treated as having priority over W. americana.

With best wishes,

Subir.