Pendulous Usnea Species (Parmeliaceae, Lichenized Ascomycota) in Tropical South America and the Galapagos
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The Lichenologist 45(4): 505–543 (2013) 6 British Lichen Society, 2013 doi:10.1017/S0024282913000133 Pendulous Usnea species (Parmeliaceae, lichenized Ascomycota) in tropical South America and the Galapagos Camille TRUONG, Juan Manuel RODRIGUEZ and Philippe CLERC Abstract: The diversity of pendulous Usnea species in tropical South America (Bolivia, Brazil, Colombia, Ecuador, Paraguay, Peru and Venezuela) and the Galapagos Islands is discussed with ref- erence to 23 species. Usnea crenulata Truong & Clerc is newly described. Usnea articulata, U. deformis, U. dimorpha, U. geissleriana, U. merrillii, U. perhispidella, U. sanctaeritae, U. subflammea and U. transi- toria are newly reported for South America. Modern descriptions are provided for Usnea amabilis, U. arthroclada, U. dodgei, U. humboldtii and U. regia. We propose to reject the synonymy of U. hesperina with U. schadenbergiana, and the valid name for U. hesperina is therefore U. subgracilis. Distinct patterns of unidentified triterpenoids have been detected by thin-layer chromatography and are used to characterize several species within this group. The morphology, branch anatomy, chemistry, ecology and distribution of each species are given, together with an identification key. Key words: endemism, lichens, macrolichens, Neotropics, taxonomy Accepted for publication 19 January 2013 Introduction 1992, 2011b; Halonen et al. 1999), Macaro- nesia (Clerc 2006), North America (Clerc & Usnea is one of the largest genera within the Herrera-Campos 1997; Halonen et al. 1998; family Parmeliaceae (Lecanorales, Ascomycota), Herrera-Campos et al. 1998, 2001; Clerc and is estimated to comprise more than 350 2008), East Africa (Swinscow & Krog 1978, species (Clerc 1998), widely distributed in 1979), Eastern Asia (Ohmura 2001, 2012; polar, temperate and tropical regions. The Ohmura et al. 2010), Australia (Stevens 1999, genus is well-characterized by a fruticose 2004), India (Awasthi 1986) and the polar thallus, branches with a cartilaginous central regions (Walker 1985; Seymour et al. 2007; axis and the presence of usnic acid in the cor- Wirtz et al. 2008; Lumbsch & Wirtz 2011). tex. The delimitation of species is consider- In the Neotropics, Usnea species are found ably challenged by the extensive plasticity abundantly in montane forests, especially close of morphological characters in response to to the tree limit (Arvidsson 1991; Sipman environmental parameters (Clerc 1998) and 1995, 1999) or in open meso-habitats in the numerous taxa have recently been reduced vicinity of the forest, such as isolated old- to synonymy. Since Motyka’s world mono- growth trees within pastures, forest borders graph (1936, 1938), taxonomic revisions have (along roads) or deforested zones of matorral been carried out in Europe (Clerc 1987b, (Truong et al. 2011). In the Galapagos, Usnea species are encountered in all vegetation belts C. Truong and P. Clerc: Conservatoire et Jardin Botani- except in the coastal zone, with the highest ques de la Ville de Gene`ve, CP 60, 1292 Chambe´sy, diversity and abundance in the transition Switzerland ; Laboratoire de Syste´matique Ve´ge´tale et zone (see Aptroot & Bungartz 2007 for de- Biodiversite´, Faculte´ des Sciences de l’Universite´ de Gene`ve, CP 60, 1292 Chambe´sy, Switzerland. Email: tails on vegetation zones), probably related [email protected] to the occurrence of fog (Truong et al. J. M. Rodriguez: Centro de Ecologı´a y Recursos Natu- 2011). Numerous Usnea species, as currently rales Renovables, Facultad de Ciencias Exactas, Fı´sicas y understood, have a cosmopolitan distribu- Naturales, Universidad Nacional de Co´rdoba, CONICET, Av. Ve´lez Sarsfield 299, Co´rdoba, Argentina. tion and the Usnea flora of South America Downloaded from https:/www.cambridge.org/core. University of Basel Library, on 30 May 2017 at 20:24:30, subject to the Cambridge Core terms of use, available at https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0024282913000133 506 THE LICHENOLOGIST Vol. 45 integrates elements from North America, cies, as well as their distribution per country tropical Africa, Macaronesia and even Asia and altitudinal ranges, is found in Table 1. (Truong et al. 2011). An ongoing taxonomic Usnea crenulata is newly described and nine investigation of the diversity of Usnea species species are newly reported for South Amer- was recently started in South America and ica. Usnea alata, U. crenulata and U. regia the Galapagos (Rodriguez et al. 2011; Truong are so far endemic to South America, where- et al. 2011; Truong & Clerc 2012). It con- as U. amabilis, U. arthroclada, U. deformis, U. tributes to further elucidate the level of dodgei, U. firma, U. humboldtii, U. malmei, endemism in the Galapagos, as well as pro- U. mexicana, U. papillata, U. sancteritae and viding a better understanding of this genus U. transitoria are so far endemic to the Neo- worldwide. This study is a further step, treat- tropics (occurring in Central America as ing the pendulous species from tropical well). Usnea mexicana and U. dodgei occur in South America and the Galapagos. the Galapagos, but also on the South Ameri- can mainland. For each species, CMA values and A/M Materials and Methods ratios are illustrated in Fig. 1. They have This study is based mainly on material collected by the proved to be very good diagnostic characters authors in Bolivia, Ecuador (including the Galapagos) in the delimitation of Usnea species (Clerc and Peru, as well as herbarium specimens collected in 1998; Truong et al. 2011). Brazil and Paraguay by K. Kalb (private hb.) and A. The species exhibit one to four chemo- Spielmann (SP), in Colombia by H. Sipman (B) and in types that are described in Table 2. Triterpe- Venezuela by M. E. Hale, Jr. (US). See Truong et al. (2011) for a detailed description of the collection sites. noids have been previously reported from Specimens and types from the following herbaria were North American (Halonen et al. 1998) and included: BM, G, H, LBL, MEXU, OXF, S, TUR, eastern Asian (Ohmura 2001) species, and UPS, W and WU. Only names that have been cited in seem to be particularly abundant in Neo- South America are mentioned in the list of synonyms in the species descriptions. tropical species (Truong et al. 2011). Their Morphology of specimens was examined using a Leica detection is realized under the UV lamp after MS5 stereomicroscope. See previous publications (e.g. charring (before that step, they are often Clerc 1987a, 1998, 2011b; Clerc & Herrera-Campos undetectable or may be mistaken for fatty 1997; Herrera-Campos et al. 1998; Ohmura 2001; acids). Although the exact nature of these Truong et al. 2011) for detailed descriptions of the char- acters used in the delimitation of Usnea species. Shape of triterpenoids remains unknown, they occur branch and branch segments are especially valuable to in distinctive patterns, as illustrated in Fig. describe pendulous Usnea species and an illustration of 2. These patterns are often characteristic these characters is provided in Clerc (2011b). In the of each species and can be used for their species descriptions, the size of soralia and tubercles will be referred to as minute (less than the half-branch identification. diameter) or large (more than the half-branch diameter). Anatomical measurements of cortex, medulla and Thallus erect versus pendulous central axis were realized in longitudinal section of branch at Â40 magnification. The percentage thickness By definition, a pendulous thallus exhibits of cortex/medulla/axis of the total branch diameter branches running parallel almost from the (CMA) and the ratio of axis/medulla (A/M) were calcu- lated according to Clerc (1987b). In the description of base to the apices, and hanging downwards species, CMA values are given with their standard de- (see illustrations in Herrera-Campos et al. viations and follow the categories described by Clerc 1998; Ohmura 2001). Usnea angulata, U. (2011b). malmei and U. subgracilis are typically pen- Chemical analyses were performed by thin-layer chro- matography (TLC) following the method of Culberson dulous. In subpendulous thalli, branches are & Ammann (1979), with solvent B modified according first diverging and erect, then rapidly run to Culberson & Johnson (1982). parallel and hang down, at least before reach- ing half of the thallus length. Usnea dodgei Results (Fig. 7D), U. geissleriana and U. subscabrosa are typically subpendulous. In erect thalli, A total of 905 specimens were studied. The branches remain erect and divergent to the number of specimens studied for each spe- apices. Although pendulous thalli are usually Downloaded from https:/www.cambridge.org/core. University of Basel Library, on 30 May 2017 at 20:24:30, subject to the Cambridge Core terms of use, available at https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0024282913000133 2013 Pendulous Usnea in tropical South America—Truong et al. 507 Table 1. Distribution per country and altitudinal ranges of the pendulous Usnea species in tropical South America and the Galapagos Islands. Altitude Species n BOL BRA COL ECU GAL PAR PER VEN Altitude (SAM) (GAL) U. alata 17 + + + 150–1400 U. amabilis 43 + + + + + (900) 1700–2950 U. angulata 184 + + + ext + + + (0) 500–3050 U. arthroclada 23 + 1600–1850 U. articulata* 3 +? U. crenulata*** 26 + + + + 2100–3100 U. deformis* 12 + + + + 2200–4200 U. dimorpha* 26 + + + + + (500) 2000–3500 U. dodgei 50 + + + + + (450) 1000 - 3000 150–1100 U. firma 33 + 1500–2000 U. geissleriana* 16 + + + + + (900) 2400–3200 U. humboldtii