Petrova O. The lichen genus Usnea in eastern Gennoscandia. III Shrubby species. Ann. Bot. Fennici. 1999, 36, p. 235-256.

ANN. BOT. FENNICI 36 (1999) • Usnea in East Fennoscandia. III. 249 dant, usually present also near apical parts. Soralia ( see Clerc 1987b: 101, Halonen et al. 1998: 39), when mature, normally deeply excavate with torned cortex around them, first ± widely spaced, later often encircling the whole branch and even becoming confluent; soredia usually farinose. Isidia absent, but sometimes tuberculate soralia may contain spinules. Chemistry . Strain 1 ( n = 166): usnic + salazinic ± protocetraric (trace) acids ± fatty acids (2 speci- mens) (K+ yellow, orange or red, PD+ yellow or orange); strain 2 ( n = 8): usnic + salazinic + cape- ratic ± protocetraric (trace) acids (K+ yellow, or- ange or red, PD+ yellow or orange); strain 3 ( n = 7): usnic acid (K–, PD–); strain 4 ( n = 6): usnic + psoromic + 2’- O -demethylpsoromic acids (K– or K+ yellow, PD+ yellow). This is the only East Fennoscandian species with a psoromic acid strain. This chemotype is southern in Usnea lapponica in Europe (Clerc pers. comm . ). Remarks . Usnea lapponica is closely related to U. substerilis . The latter is distinguished by the superficial, tuberculate to slightly excavate soralia, which normally have granulose soredia and may also develop isidia. Furthermore, young soralia of U. lapponica are normally more widely ar- ranged (later often becoming ± confluent) than young soralia of U. substerilis which usually are, especially near apical parts, arranged in clusters of minute soralia which become confluent form- ing larger soralia patches. There also are some chemical differences, since barbatic acid is not found in U. lapponica in East Fennoscandia, al- though the compound is very rarely present in British Columbia specimens (Halonen et al. 1998). On the other hand, U. lapponica may produce psoromic or caperatic acid which are not found in U. substerilis . These two species often are diffi- cult to distinguish since some modifications of U. lapponica , especially compact morphs, may have tuberculate soralia with isidia-like spinules and the isidia may be abraded in U. substerilis . Furthermore, in a late stage soralia of U. substerilis may become confluent with eroded soredia, thus resembling soralia of U. lapponica . Specimens that cannot be determined with certainty could be named as U. lapponica s. lato. Ecology . The species has been collected main- ly from Picea (31%), Betula (22%) and Alnus (13%), and less frequently from Sorbus , Pinus , Salix , Populus , Prunus , Quercus , Acer , Tilia , La- rix , Juniperus and lignum (in total 239 specimens). Usnea lapponica has a wide ecological amplitude occurring both in open and dense forests, in gar- dens and on roadside trees, but it avoids very dry sites. Distribution . Finland: 1–19, 21; Russia: 1–5, 8, 10–13, 17. World distribution: northern circum- polar, hemiarctic to temperate. According to Clerc (1992), Usnea lapponica has a continental distri- bution in Europe. The species has a wide range from the south coast to the northern parts of Lap- land and the Kola Peninsula. Usnea lapponica seems to be locally the most common shrubby Usnea species in northern provinces, but it is rare in Åland and may have slightly eastern tenden- cies in its distribution. Selected specimens examined . — Finland . Åland: Eckerö, Storby, Käringsund, 1949 Häyrén (H), strain 1. Etelä-Häme: Sääksmäki, Ikkala, Uotila, 1932 Linkola (H), strain 2. Laatokan Karjala: Saari, Honkakylä, Kiiveri, 1932 Räsänen (H), strain 1. Etelä-Pohjanmaa: Vaasa, 1957 Bäck (H), strain 4. Kainuu: Kuhmo, Siikasalmi, 1956 Railonsala (Räsänen, Lichenoth. Fenn. no. 960, H, OULU, S, TUR, sub “ U. sorediifera ”), strain 1. Koillismaa: Kuusamo, Toran- ginaho, 1960 Ahti 11884 (H), strain 3. Kittilän Lappi: Kittilä, Uotivuoma, 1908 Lång (H), strain 1. Inarin Lappi: Inari, Kaunispää, 1936 Ahlner (S), strain 4. Russia . Leningrad Region. Karelia australis: Yashino (Vahviala), Hämeenvaa- Fig. 6. Foveoles (pointed by arrows) on branches of Usnea lapponica Vain. From 1966 Takala 2844 (H). Scale = 1.3 mm.