Flora of New Zealand Series

Type : Physcia tenella (Scop.) DC.  nom. cons. [=Lichen tenellus Scop.]

Description : Flora (1985: 391). Physcia is recognised by the following characters: Thallus foliose, pale-grey to very dark-grey, unchanged when wet, sometimes with a white pruina. Lower surface white to brownish with whitish to black, simple rhizines. Upper cortex paraplectenchymatous, of isodiametric cells; lower cortex of longitudinally arranged cells. Ascomata apothecia, lecanorine without rhizines at base. Ascospores 1-septate, brown, rarely exceeding 25 μm, thick-walled. Asci Lecanora -type (Rambold et al. 1994). Conidiomata pycnidia. Conidia bacillar, 4–6 μm long. Atranorin always present in upper cortex (K+ yellow).

Physcia is a cosmopolitan genus of c. 70 species (Moberg 1994b, 2002b), included in the family Physciaceae nom. cons. (Eriksson et al. 2004; Pennycook & Galloway 2004; Eriksson 2005). European and Scandinavian taxa were monographed by Moberg (1977, 2002g). Since then he has monographed taxa from East Africa (Moberg 1986b), Greenland (Moberg & Hansen 1986), Central and South America (Moberg 1990; Elvebakk & Moberg 2002), Australia (Moberg 2001), the Sonoran Desert and adjacent areas (Moberg 1997, 2002b) and South Africa (Moberg 2004b), his accounts giving much useful information on anatomy, morphology and distribution of taxa. Seven species of Physcia were recorded in the Flora (Galloway 1985a), but since that time extensive collecting in urban, coastal and inland areas from Whangarei to Invercargill has disclosed an additional seven species, with 14 species now known from New Zealand (Galloway & Moberg 2005).

Several taxa are recorded as hosts for the lichenicolous heterobasidiomycete, * Syzygospora physciacearum Diederich (Diederich 1996), but so far no material of this species is recorded from New Zealand collections of Physcia. On the other hand, coastal specimens of Physcia caesia are parasitised by * Polycoccum pulvinatum (Eitner) R.Sant. (q.v.), but it appears to be absent from inland localities (Galloway et al. 1999).

Material from Nelson identified as P. semipinnata (J.F.Gmel.) Moberg. [=P. leptalea (Ach.) DC.] (Malcolm & Malcolm 2001: 40, 51) is referable to Heterodermia, as the specimen collected has a prosoplectenchymatous upper cortex (Galloway & Moberg 2005).

In a reappraisal of the phylogenetic relationships of the Physciaceae inferred from both molecular data and phenotypic characters, Helms et al. (2003), emend the concept of Physciaceae Zahlbr. to include taxa united by asci of Lecanora -type, a hyaline hypothecium, and ascospores with distinct wall thickenings or of Rinodinella -type. This allows the family Caliciaceae Chevall. to co-exist in an emended definition, viz. ascis of Bacidia -type or prototunicate, a pigmented hypothecium, and ascospores without distinct wall thickenings.