Flora of New Zealand Series

Type : Porpidia trullisata (Kremp.) Körb. [=Diplotomma trullisatum Kremp.]

Description : Thallus crustose, thick to inconspicuous, tartareous, continuous to areolate, grey white or rust-coloured. Prothallus present (mainly between adjacent thalli) or absent, black, thin. Medulla I+ or I−. Soredia present or absent (no sorediate taxa currently known fron New Zealand). Photobiont green, chloroccoid. Ascomata apothecia, apothecia scattered or clustered, sessile to immersed, rather large, to 4 mm diam., often separated from the thallus by a narrow to wide crack; disc dark-brown to black, sometimes umbonate, pruinose or not, with a distinct proper exciple. Exciple dark-brown, to greenish brown, or pigmented in outer parts and colourless internally, of conglutinated, radiating hyphae. Hymenium 80–150 μm tall colourless, I+ blue; epithecium brown to greenish brown, N+ rose-pink to purple. Hypothecium colourless in upper parts (subhymenium) elsewhere dark-brown to brown-black. Hamathecium of paraphyses, septate, branched-anastomosing, netted, slightly swollen at apices but without dark-brown apical caps. Asci 8-spored, clavate to subcylindrical, Porpidia -type (Pietschmann 1990; Malcolm & Galloway 1997: 197). Ascospores, simple, colourless, rather large, ±ellipsoidal, halonate, perispore 2–7 μm thick. Conidiomata pycnidia, rare, immersed. Conidia bacillar.

Species of Porpidia are included in the family Porpidiaceae (Hafellner 1984; Eriksson et al. 2004; Pennycook & Galloway 2004; Eriksson 2005) and are characterised by sessile to subimmersed apothecia; a dark brown-black carbonaceous exciple which is ±continuous with the hypothecium; an I+ blue hymenium; a distinctive ascus type [Porpidia -type with an apical amyloid tube structure in the tholus (see Pietschmann (1990) for a useful discussion), though recent molecular studies cast doubt on the phylogenetic importance of this character (Buschbom & Mueller 2004)]; large, halonate ascospores; and branched paraphyses. Formerly treated as Haplocarpon Choisy (Hertel 1973) and Huilia Zahlbr. (Hertel 1975b, 1977a; Galloway 1985a), Porpidia comprises c. 16 species worldwide (Buschbom & Mueller 2004; Knoph & Rambold 2004). The genus is still poorly collected and understood in the Southern Hemisphere, and much work still needs doing on New Zealand populations. Useful discussions of the genus are given in Inoue (1983a, 1983b, 1983c); Hertel (1984b, 1985b); Hertel & Knoph (1984); Schwab (1986); Gowan (1989a, 1989b); Rambold (1989); Galloway & Coppins (1992b); Gowan & Ahti (1993); Knoph & Rambold (2004), and Fryday (2005). A recent molecular study (Buschbom & Mueller 2004) of Porpidia and allied genera showed Porpidia s.lat. to comprise four distinct subgroups (one of which includes Lecidea), whose taxonomic rank will need to be determined in a future revision of the group based on molecular and non-molecular characters. Porpidia in its present circumscription is therefore polyphyletic. Seven species are presently known in New Zealand from lowland to alpine environments.