Flora of New Zealand Series

=NEUROPOGON Nees & Flot., 1835

=EUMITRIA Stirt., 1881

Type : Usnea plicata (L.) A.L.Sm. [=Lichen plicatus L.]

Type : Neuropogon antennarius Nees & Flot. [Usnea aurantiaco-ater (Jacq.) Bory]

Type : Eumitria baileyi Stirt. [=Usnea baileyi (Stirt.) Zahlbr.]

Description : Flora (1985: 596).

Usnea, included in the family Parmeliaceae (Eriksson et al. 2004; Pennycook & Galloway 2004; Eriksson 2005), comprises c. 300 species worldwide (Kirk et al. 2001). Although Usnea is one of the most readily recognised and easily collected of fruticose lichen genera, it still remains poorly understood at the species level, because of the often extreme plasticity of such characters as colour, length of thallus branches, density of branching, development and density of fibrils, shape of papillae, presence of faveolae, and thickness of growth apices (Clerc 1991). According to Clerc (1984a, 1987a, 1987b, 1998) the best diagnostic morphological characters in Usnea are: (1) colour and frequency of segementation of the basal portions of the thallus, (2) shape of the secondary branches, (3) dominant branching patterns, (4) type of soralia, and (5) details of the internal structure. The shape and density of papillae and the density of fibrils are also useful but appear to be modified to a large extent by environmental factors. The colour of the living thallus has only minimal diagnostic value, except when other pigments in addition to usnic acid are present. A ±well-developed internal prosoplectenchymatous medullary cord is a characteristic feature of the genus (see Wright 1999). Apothecia, when present, are zeorine, characterised by a double-layered exciple. Asci are Melanelia -type. Pycnidia are laminal and immersed. Conidia are sublageniform (Kärnefelt et al. 1998: 87, fig. 5F). Recent molecular work on the Usnea florida – U. subfloridana species-pair, distinguished mainly by their dispersal strategies, with U. florida being the fertile, primary species and U. subfloridana the derived, sterile, secondary species, has shown them to be one monophyletic group of intermixed specimens (Articus et al. 2002). This result has major consequences for our understanding of "species-pairs" in both Usnea and other lichen genera.

Although the Usnea monograph of Motyka (1936, 1937, 1938, 1947) is still an important, though outdated, resource for many areas of the world, including New Zealand, in recent years taxonomic work on Usnea has revived in the Northern Hemisphere and modern methods have been used in several important regional studies, viz. Swinscow & Krog (1974, 1975c, 1976a, 1976c, 1978b, 1979a, 1986b, 1988) for East Africa; Clerc (1984a, 1987b, 1991, 1992, 1994, 1997), Clerc & Diederich (1991), and Fos & Clerc (2000) for Europe; Clerc (1987a, 2004), Esseen et al. (1981), Myllys (1994), Halonen & Puolasmaa (1995), and Halonen (1997) for Scandinavia; Tavares (1987, 1997), Clerc & Herrera-Campos (1997), McCune & Geiser (1997), Halonen et al. (1998), Halonen (2000), Herrera-Campos et al. (1998, 2001), and Clerc (2004) for North America including Mexico; Awasthi (1986) for India; Ohmura & Kashiwadani (2000), Ohmura et al. (2000), and Ohmura (2001, 2002) for Japan; and Rogers & Stevens (1988), Stevens (1990, 1991a, 1991b, 1992, 1999, 2004b) and Clerc (2004) for Australia. James (2003) has recently compiled an aide mémoire to the British species of Usnea, an account having useful information on species discrimination in the genus.

The Neuropogon"group" in Usnea is a bipolar assemblage of saxicolous taxa, with all but one of its 15 species confined to high-altitude rock outcrops in Arctic, Antarctic or southern cool-temperate biomes (Lamb 1939, 1948b, 1964; Galloway 1985a; Walker 1985; Stevens 1999, 2004a; Øvstedal & Lewis Smith 2001). Recent molecular studies (Ohmura & Kanda 2004) place Neuropogon as a section within subgen. Usnea. Another molecular study (Articus 2004) reached a different conclusion and confirmed that Dolichousnea, Eumitria and Neuropogon are all monophyletic, and should be treated as independent genera, but that Usnea as presently conceived is clearly non-monophyletic and requires further analysis using larger data sets. However, recently published molecular work on 12 of the 15 species known from Neuropogon (including the generitype) has indicated that Neuropogon is polyphyletic, with a core group nested within Usnea subgen. Usnea as sister-group to sect. Usnea (Wirtz et al. 2006). Accordingly, they synonymise Neuropogon with Usnea, a position followed here.

In New Zealand, Usnea is a common and widespread genus, occurring in a variety of habitats from coastal to subalpine and even high-alpine biomes. Preliminary accounts of New Zealand species are given in Galloway (1985a) and Stevens (1999), but the genus is still far from understood here and is much in need of serious revisionary study. Although large collections of Usnea exist in several major herbaria in New Zealand, it is surprising that until very recently no serious attempt has been made at a regional study of the genus, a study that would amply repay the effort invested in it. Darrell Wright (Wellington) has recently begun investigations of lower North I. populations (Wright 2003, 2004) and has already added useful information to our knowledge of New Zealand's Usnea mycobiota. The present treatment discusses 28 species, but it is still only a very preliminary account.