Lepraria Ach.
=LEPROLOMA Nyl. ex Cromb.
Type : Lepraria incana (L.) Ach [=Byssus incana L.]
Type : Leproloma lanuginosum Nyl. ex Cromb. [=Lepraria membranacea (Dicks.) Vain.]
Description : Flora (1985: 245). See also Laundon (1992: 320).
Key
Lepraria, included in Ascomycota inc. sed. (Pennycook & Galloway 2004) is a widespread genus of c. 30 species (Tønsberg 2004b). Recent molecular studies show that Lepraria should be included in the family Stereocaulaceae (Ekman & Tønsberg 2002; Eriksson et al. 2004; Eriksson 2005). Lepraria is a form genus characterised by its greyish or whitish powdery or granular, diffuse, uniform crust, and the absence of ascomata (Poelt 1987; Laundon 1992; Tønsberg 1992b). Lepraria differs from most other lichen genera in having a thallus composed entirely of a mass of tiny, spherical granules. Species of Chrysothrix, Leproloma and Leproplaca [=Caloplaca, see Jørgensen & Tønsberg 1988; Kärnefelt 1989) were sometimes formerly included in Lepraria but they are apparently not related. From a taxonomic standpoint Lepraria s. lat. is a difficult group since only a few morphological characters are available to distinguish individual taxa. However, there is a remarkable diversity in secondary chemistry, and the importance of chemistry in species delimitation in Lepraria is now well-established (Leuckert & Kümmerling 1989; Kümmerling et al. 1991, 1993a, 1993b, 1995; Laundon 1992; Tønsberg 1992b, 2002a; Kümmerling & Leuckert 1993; Lohtander 1994; Leuckert et al. 1995, 2002; Lindblom 1995; Wirth & Heklau 1995; Øvstedal & Lewis Smith 2001; Zedda 2000; Orange 2001; Kukwa 2002a; Elix & Tønsberg 2004; Sipman 2004; Bayerová et al. 2005; Elix et al. 2005c; Elix 2006a, 2006b). Botryolepraria lesdainii (Hue) Canals, Hernádez-Mariné, Gómez-Bolea & Llimona recently segregated from Lepraria (Canals et al. 1997), a decision supported by Tønsberg (2002a). The genus Leproloma Nyl. ex Cromb., originally established for the Lepraria membranacea group (Laundon 1989; Leuckert & Kümmerling 1991; Leuckert et al. 1995; Lohtander 1995; Tønsberg & Jørgensen 1997), is now reduced to a synonym of Lepraria (see Kukwa 2002b).
Molecular studies on taxa of Lepraria and Leproloma show that most species referred to these genera form a single monophyletic group. This monophyletic group is the sister group to Stereocaulon and Muhria, and belongs in the family Stereocaulaceae. This indicates that an ancestor of Lepraria switched from a sexual to an asexual mode of dispersal. Subsequent speciation must have occurred in the absence of sexual processes, which contradicts the view of asexual taxa as "evolutionary dead ends" (Ekman & Tønsberg 2002).
Species of Lepraria frequent shaded habitats, such as beneath rock overhangs, on shaded tree trunks, and roots, and on earth banks. A few species are epiphytic on mosses and other lichens, often in alpine–subalpine habitats (Laundon 1992). The leprarioid state appears to be a growth form that has arisen in response to a special habitat of dry surfaces (such as concave parts at the base of tree trunks and also on the undersides ("armpits") of large branches or leaning trunks) in sites with high humidity and low illumination. The leprarioid growth form [and similarly also with the byssoid growth form (see Rogers & Hafellner 1987)] is apparently adapted to the absorption of water vapour, allowing leprarioid lichens to colonise surfaces not wetted by waterflow or direct rainfall (Tønsberg 1992b: 194). Six species are recorded from New Zealand, but the genus is still very poorly known and collected here and more taxa can be confidently expected to occur, especially in alpine areas.
