Unguiculariopsis triregia is most closely related to the recently described U. ahtii HAWSKW., GALLOW. et KONDR. and the more common U. thallophila (P. KARST.) ZHUANG. It differs, however, from both in having apothecia arising in groups up to 4 (in U. thallophila and U. ahtii they are solitary), in having a more differentiated and darker epithecium and thickened, agglutinated Paraphyses at the tops (in contrast, no differentiated epithecium is found in U. thallophila, and slightly darker, unthickened Paraphyses are seen at the tops in U. ahtii). Moreover, U. triregia differs from U. thallophila in the much larger apothecia (see above, 200 - 400 µm in U. thallophila), much longer and narrower asci (see above, 35 - 40 x 6 - 10 µm in U. thallophila, HAWKSWORTH [1980]). U. triregia differs from U. ahtii in having well distinct outer hairs at the tops of some exciple cells (see above, ± indistinct hyaline cells in U. ahtii), in having a much darker and thicker epihymenium (orange-brown, 9.0 - 12.5 µm tall in U. ahtii), and in having smaller and wider ascospores (9 - 12.5 x 1.5 - 2.0 µm in U. ahtii, cf. KONDRATYUK et al. 1994).

Unguiculariopsis triregia differs from U. cribriformis (NORM.) ALSTRUP et HAWSKW. in ascospore shape (globose, 5.0 - 5.5 [-6.0] µm diam.) and different hosts (U. cribriformis: Pertusaria [ALSTRUP and HAWKSWORTH 1989]). U. triregia as well as U. ahtii, U. cribriformis, and U. thallophila differ from all known species of Skyttea by having superficial apothecia at maturity, with asci having a thick homogeneous wall without distinct apical cap, globose excipular cells as well as by the absence of a greenish pigmentation of the exciple and hairs. U. triregia is the fifth known lichenicolous species of this mainly fungicolous genus.