Parmotrema diffractaicum (Essl.) Hale, 1974
Diagnostic description:
Parmotrema diffractaicum is distinguished by the pustular to capitate soralia, the lower naked marginal zone and the presence of diffractaic acid (medulla CK+ orange) and lichexanthone (medulla UV+ yellow-orange). Parmotrema pontagrossense (Eliasaro & Adler) Blanco, Crespo, Divakar, Elix & Lumbsch produces salazinic acid (medulla K+ yellow → blood red) and P. bonplandii (Mata) Blanco, Crespo, Divakar, Elix & Lumbsch is a similar, but isidiate species (Mata García 1994).
Rimelia luminosa Marcelli (in Marcelli & Ribeiro 2002) was recently recognized as a synonym of P. diffractaicum (Marcelli & Canêz 2008).
[Spielmann & Marcelli 2008]