Polar Biol (2012) 35:1143–1149 DOI 10.1007/s00300-012-1161-z ORIGINAL PAPER The polar lichens Caloplaca darbishirei and C. soropelta highlight the direction of bipolar migration U. Søchting • M. Castello Received: 31 October 2011 / Revised: 3 February 2012 / Accepted: 7 February 2012 / Published online: 24 February 2012 Ó Springer-Verlag 2012 Abstract A proper phytogeographic affiliation of Antarctic lichen species has become feasible using molecular phylogeographic methods. Caloplaca citrina is a heterogeneous taxon including several species which occurs in polar regions and is common in Antarctica. Collections of C. citrina from the Antarctic were revised using morphological, anatomical and molecular characters (ITS). They were found to belong to two species: Caloplaca darbishirei (C.W. Dodge & G.E. Baker) Cretz. and C. soropelta (E.S. Hansen, Poelt & Søchting) Søchting. The molecular phylogeny showed them to be sister species, but well separated. Morphological and chemical characters, ecology and distribution of the species are discussed. C. darbishirei is the most common species in the Antarctic, and it is so far known only from Antarctica and Southern South America. C. soropelta, reported here as new to South America, is a bipolar species with all close relatives in the Southern Hemisphere; it is therefore most likely that the species colonized the Arctic from the south. C. citrina s. str. is not confirmed to occur in Antarctica. The study emphasizes the suitability of genotyping for understanding the taxonomy and phylogeography of bipolar lichens. U. Søchting (&) Section of Ecology and Evolution, Department of Biology, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen Ø, Denmark e-mail: ulriks@bio.ku.dk M. Castello Department of Life Sciences, University of Trieste, Via Giorgieri 10, 34127 Trieste, Italy Keywords Antarctica
Bipolar
Caloplaca citrina
ITS
Phylogeography
Long-range dispersal Introduction With about 30 species, the genus Caloplaca is one of the largest lichen genera in Antarctica (Søchting and Olech 1995; Øvstedal and Lewis Smith 2001; Søchting et al. 2004). Being represented with an equally high diversity in the Arctic, the genus is well suited for studies of polar phylogeography based on molecular data. One of the most frequently collected Caloplaca from Continental Antarctica is a sorediate species occurring on bryophytes, plant debris, soil or rock, particularly abundant in sites near bird colonies both in continental and the maritime Antarctic, and it has since long been referred to as C. citrina (e.g., Øvstedal and Lewis Smith 2001; Olech 2004). This name has been used world-wide in a very broad sense reflecting a poor understanding of a highly variable taxon. We have suspected for a long time that the C. citrina of the Antarctic differed from what was called C. citrina elsewhere, but a thorough understanding was only recently made possible, after two comprehensive studies from the Northern Hemisphere including molecular data consolidated the concept of the species in the Caloplaca citrina aggregate (Arup 2006; Vondrák et al. 2009). The aim of the present study was to improve the understanding of the taxonomy and distribution of the so-called C. citrina from Antarctica. We performed a morphological and molecular analysis of Antarctic sorediate specimens formerly assigned to C. citrina, examined their phylogenetic positions and mapped their distributions. 123 1144 Polar Biol (2012) 35:1143–1149 Materials and methods Morphology and chemistry The study is based on all available collections labeled C. citrina from Trieste (TSB), Copenhagen (C), British Antarctic Survey (AAS) and Australian Antarctic Survey (HOB), for a total of 158 specimens. Morphological features were studied with a dissection microscope. Anatomical features were studied with a compound light microscope. Sections 7 lm thick were made on a Reichert-Jung Cryostat 2,800 Frigocut-E. Sections mounted in water were used for anatomical studies and measurements of structures. Photographs were taken with a Nikon DS-Fi1 digital camera mounted on an Olympus SZH Macroscope. Secondary chemistry was studied with HPLC according to Søchting (1997), and the chemosyndrome nomenclature follows Søchting (1997). DNA analysis 14 specimens of C. citrina from Antarctica and Southern South America, 7 other Caloplaca specimens and one Xanthoria were subjected to a phylogenetic analysis based on the ITS region of nuclear rDNA. The analyses were performed with direct PCR (Arup 2006) using the primers ITS1F (Gardes and Bruns 1993) and ITS4 (White et al. 1990), and the PCR program of Ekman (2001). The same primers were also used to sequence the total ITS (ITS15.8S-ITS2) from the nuclear rDNA. Sequencing was done by Macrogen Inc. in Korea. Sequences were assembled and manually aligned with CLC Main Workbench version 4.1.2. Sequences have been submitted to GenBank as indicated in Table 1. Phylogenetic analysis The phylogenetic analysis included 14 specimens of the Antarctic/Southern Patagonian C. citrina complex, one of C. soropelta from the Northern Hemisphere, four of C. millegrana, two of C. hookeri; Xanthoria elegans was chosen as the out-group. Data were analyzed using the program MrBayes 3.1 (Huelsenbeck and Ronquist 2001; Ronquist and Huelsenbeck 2003). The nucleotide substitution model GTR?G was selected using the program Jmodeltest 0.1.1 (Posada and Crandall 1998). No molecular clock was assumed. Table 1 Voucher specimens and GenBank accessions numbers of the ITS sequences used in the phylogenetic analysis Species USE Voucher GenBank accession number Caloplaca darbishirei 3276 Antarctica, Adelaide I., 2011, US 11394 (C) JQ074192 C. darbishirei 3282 Antarctica, Adelaide I., 2011, US 11401 (C) JQ074193 C. darbishirei 2829 Antarctica, Victoria Land, Crater Cirque, 2006, A924 (TSB) JQ074196 C. darbishirei 2833 Antarctica, Victoria Land, Granite Harbor, 2006, A922 (TSB) JQ074198 C. darbishirei C. darbishirei 1560 1563 Antarctica, Victoria Land, Apostrophe Island, 2006, A930 (TSB) Antarctica, Victoria Land, Cape King, 2006, A931 (TSB) JQ074194 JQ074195 C. darbishirei 1554 Antarctica, Victoria Land, Harrow Peaks, 2006, A927 (TSB) JQ074199 C. darbishirei 3270 Antarctica, Adelaide I., 2011, US 11391 (C) JQ074191 C. darbishirei 3152 South Shetland Is., Deception I., R.I.L.Smith 11.193 (AAS) JQ074197 C. darbishirei 3156 South Shetland Is., Deception I., R.I.L.Smith 11.391 (AAS) JQ074200 C. hookeri 3221 Chile, Tierra del Fuego, 2009, US 11271 (C) JQ074201 C. hookeri 3174 Chile, Tierra del Fuego, 2009, US 11344 (C) JQ074202 C. millegrana 910 Chile, Navarino Isl., 2005, US 10350 (C) C. millegrana JQ074203 3206 Chile, Tierra del Fuego, 2009, US 11299 (C) JQ074205 C. millegrana 3201 Chile, Tierra del Fuego, 2009, US 11329 (C) JQ074204 C. millegrana 912 Chile, Navarino Isl. 2005, US 10176a (C) JQ074206 Antarctica, Victoria Land, Inexpressible Island, 2006, A928 (TSB) JQ074207 JQ074211 C. soropelta 1551 C. soropelta 203 Iceland, Myvatn, 1997, US 7536 (C) C. soropelta 713 Chile, Navarino Isl., 2005, US 10387 (C) JQ074208 C. soropelta 2836 Argentina, Southern Patagonia, 2005, US 10421 (C) JQ074209 C. soropelta Xanthoria elegans 2846 594 Chile, Torres del Paine, 2008, MZS 59 (C) Greenland, 2005, US 10455 (C) JQ074210 JQ074212 All sequences have been produced during this study 123 Polar Biol (2012) 35:1143–1149 A run with 2,000,000 generations starting with a random tree and employing 12 simultaneous chains was executed. Every 100th tree was saved, and the initial 5,000 trees were discarded as burn-in. The resulting 15,000 trees were used for reconstruction of a 50% majority-rule consensus tree and calculation of Bayesian posterior probabilities. The consensus tree was constructed using Treeview 1.6.6 (Page 1996). Results Molecular results The ITS sequences of the Antarctic/Southern Patagonian C. citrina were blasted against a local database of ITS sequences of Teloschistaceae that revealed a close relationship to Southern Hemisphere species such as C. hookeri and C. millegrana. No sequences had any similarity to species of the true C. citrina group discussed by Arup (2006). Furthermore, some of the Antarctic sequences appeared to be identical with the ITS sequence of C. soropelta (E. S. Hansen, Poelt & Søchting) Søchting, a species known from the Arctic and initially described as a subspecies of C. citrina (Hansen et al. 1987; Søchting 1992). The consensus tree (Fig. 1) shows that the Antarctic specimens are located in two monophyletic sister clades, which are both highly supported and closely associated 1145 with other Antarctic/Southern Patagonian species, such as C. millegrana and C. hookeri. Morphology The morphological analysis of Antarctic C. citrina specimens revealed two distinct morphotypes. One is essentially similar to C. soropelta. The other type is so common in Antarctica that it was assumed that it had already been described in the past as a species from the Antarctic. Our studies of the taxa reported by Dodge (1973) for the Antarctic lichen flora suggested that C. darbishirei (C.W. Dodge & G.E. Baker) Cretz. could be an available name for this taxon; the subsequent study of the type material from FH confirmed that it was morphologically identical to it (see also Castello and Nimis 1995a). Discussion Taxonomy and nomenclature Based on morphological and molecular data, examined collections labeled as C. citrina from Antarctica and Southern Patagonia were found to correspond to two different taxa. The type material and additional specimens from Dodge’s collections at the Farlow Herbarium (FH) that we have Fig. 1 Fifty percent majorityrule consensus tree based on 15.000 trees from B/MCMC tree sampling. Figures represent posterior probabilities 123 1146 studied leave no doubt that the correct name for one of the taxa is C. darbishirei (C.W. Dodge & G.E. Baker) Cretz. In the protologue of Pyrenodesmia darbishirei, Dodge and Baker (1938) do not mention the presence of soralia, but describe the areole margin as crenulate and the species as sterile. Later, Dodge (1973) reports in the description of the taxon that apothecia are rare and gives details of apothecium morphology and anatomy. However, Øvstedal and Lewis Smith (2001) have only found one apothecium among the numerous specimens they have studied and we have not been able to find any apothecia belonging to P. darbishirei in the type material. On the other hand, it is clear from Dodge and Baker (1938) that the most common yellow Caloplaca (as Pyrenodesmia) species occurring on mosses in Antarctica are either Caloplaca (Pyrenodesmia) darbishirei or the mostly very fertile C. (Pyrenodesmia) athallina. Other Antarctic and particularly South Patagonian collections conform to C. soropelta. C. soropelta is morphologically and molecularly very close to C. darbishirei. It is characterized by the initially convex lobes that eventually expose a well-developed rim of more golden yellowish soredia, whereas C. darbishirei has squamules with a more crenulated border with soredia of the same color as the thallus. The two species are, however, not always easy to separate. They are both nitrophytic species, growing in eutrophicated sites, often on mosses or rocks near bird colonies, and they may occur together. Carroll W. Dodge has a reputation for having described new lichen species more or less disregarding taxa earlier described from both the Northern Hemisphere and from the Antarctic (Hertel 1987, 1988; Fryday 2011). The species he described from the Antarctic were revised by several authors; for a commented list, see Castello and Nimis (1995a). Strongly supported by badly developed or missing type material and ambiguous descriptions, there has been a trend in the last decades to ignore the taxa described by Dodge, and Fryday (2011) even suggested a general rejection of all Dodge’s names. However, recent studies have shown the Antarctic lichen flora to be more diverse than earlier expected and new species names need to be applied to peculiar Antarctic populations. Names coined by Dodge may thus be available or revaluated to represent accepted taxa. Within the genus Caloplaca, this has already been the case for C. johnstonii (C.W. Dodge) Søchting & Olech, C. schofieldii C.W. Dodge and C. hookeri (C.W. Dodge) Søchting, Øvstedal & Sancho. Distribution and dispersal With some localities in Tierra del Fuego, it is likely that C. soropelta could also be found further north in the Andes, but it is significant that it has been recorded from neither 123 Polar Biol (2012) 35:1143–1149 North America nor the Alps in Europe. It is very rare in Greenland and on Svalbard, but locally abundant in Iceland (see under the species). Further studies may show it to occur also in Siberia and Alaska. C. soropelta belongs to a phylogenetic clade that consists of numerous, exclusively Southern Hemisphere species, of which many have successfully colonized the Southern cold sea shores. Its Southern origin is supported by the occurrence of the closely related species C. darbishirei on detritus and moribund mosses in Antarctica. If we hypothesize that C. soropelta has a northern origin, it should be the unlikely ancestor of numerous Southern Hemisphere circumpolar species. A distribution pattern like that of C. soropelta, although with a wider distribution in the Northern Hemisphere, is known for Xanthomendoza borealis, which is also a regular colonizer of moss cushions in Continental Antarctica together with C. darbishirei and C. soropelta. Based on phylogenetic evidence, this species was, however, assumed to have migrated from the Arctic (Lindblom and Søchting 2008). As the available morphological and molecular results disclose no divergence between the two polar populations of C. soropelta and its occurrence in the Arctic is still sporadic, the dispersal may have taken place in recent times. It is, however, not likely that such dispersal has taken place with humans since the Arctic localities are not in any way associated with human settlements in the Arctic. The limited number of true bipolar species indicates that some long-range transport of propagules may occur, although rarely. Few direct vectors for soredia are available, for example, whaling boats, polar research ships and Arctic terns (Sterna paradisaea). However, means of bipolar dispersal seem at this time to be highly speculative. The species Caloplaca darbishirei (C.W. Dodge & G.E. Baker) Cretz. Bul. Gräd. Bot. Mus. Univ. Cluj 21: 140 (1941). Pyrenodesmia darbishirei C.W. Dodge & G.E. Baker, Ann. Mo. Bot. Gard. 25: 620 (1938); type: Antarctica, Marie Byrd Land, Edsel Ford Range, Skua Gull Peak, 76°500 S145°300 W. Muscicole. Second Byrd Antarctic Expedition, P. Siple, F. A. Wade, S. Corey & O.D. Stancliff, 72 W-14 (FH!-holotype). Morphology Thallus squamulose forming up to 2-cmlarge crusts on moss; squamules up to 1.2 mm, scattered or contiguous, irregular with mostly incised to crenulated margin; surface rugged, initially mostly flat, but sometimes strongly convex, later slightly concave, orange yellow. Soralia always present, mostly discrete, sometimes lipshaped, developing from the margins of the squamules; Polar Biol (2012) 35:1143–1149 1147 eventually, a uniform sorediate crust may be formed; soredia 25–35 lm diam., concolorous with the thallus (Fig. 2). Pycnidia not seen. Secondary chemistry All screened specimens have high concentrations of parietin and small proportions of teloschistin, fallacinal, parietinic acid and emodin corresponding to chemosyndrome A (Søchting 1997). Ecology Caloplaca darbishirei is one of the most abundant species of Caloplaca in Continental Antarctica. It appears to be a strong competitor on moss cushions, where it forms yellow to orange crusts. Community studies made by Castello and Nimis (1995b) in Victoria Land, Continental Antarctica, list C. darbishirei (as C. citrina) as a member of common muscicolous and nitrophilous communities codominated by Xanthomendoza borealis (as Xanthoria mawsonii), Candelariella flava and Physcia caesia and characterized by the strictly muscicolous species Caloplaca athallina, Lecanora expectans and Lecidella siplei. C. darbishirei may rarely grow on sandy soil and rock. Fig. 3 C. soropelta (Antarctica, Inexpressible Island, TSB A928). Scale 1 mm Distribution Caloplaca darbishirei occurs in all ice-free parts of Antarctica that are close to the sea (Fig. 3), but seems to be less dominant in the maritime Antarctic than in continental Antarctica. There is so far only one record from South America, but the species is assumed to be more widespread at least in Southern Patagonia. Selected specimens examined Antarctica: Antarctic Peninsula, James Ross Isl., Dagger Peak, 15 m, top of large boulder used as skua and tern perch, i. 1989, R.I.L. Smith 7802 (AAS); Loubet Coast, Maguerite Bay, Léonie Isl., 29 m, moss on vertical, N-exposed rock, i. 2011, Søchting 11391 (C); Ellsworth Land, Eights Coast, 1 mile N of Pillsbury Tower, on ledge with associated bird bones and droppings, on pinnacle on diorite dyke in granite, vii. 1984, R.I.L. Smith 5400B (AAS); Victoria Land, McMurdo Dry Fig. 2 C. darbishirei (Antarctica, Apostrophe Island, TSB A930). Scale 1 mm Fig. 4 Distribution map of C. darbishirei Valleys, Lower Marshall Valley, 439 m, along cracks in layered gneiss of dyke, i. 2009, Seppelt 27560 (HOB); Granite Harbor, The Flatiron, 40 m, on Sarconeurum and sandy gravel in moraine debris, xi. 1994, Seppelt 19750 (HOB); Hallett Peninsula, Victory Mts., Crater Cirque, i. 2006, Bargagli A924 (TSB); Lady Newnes Bay, Cape King, 17. i. 2006, Bargagli A931 (TSB); Wood Bay, Harrow Peaks, 15. i. 2006, Bargagli A927 (TSB); Cape Hallett region, Salmon Cliff, on small pebble, in sand among boulders and scree debris, xi. 2004, Seppelt 25111 (HOB); Wilkes Land, Windmill Islands, Bailey Peninsula, ii. 1989, Seppelt 18376 (HOB); Ingrid Christensen Coast, Vestfold Hills, NW of Lichen Valley, i. 1979, Seppelt 8870 (HOB); Rauer Islands, Sapozhok Island, xii. 1983, Cracknell R207 (HOB); Mac. Robertson Land, Forbes Glacier, on Bryum pseudotriquetrum, ii. 1972, Seppelt 1001 (HOB); Kemp Land, Oy Gardens, 0–10 m, frost-shattered boulders 123 1148 Polar Biol (2012) 35:1143–1149 separated by gravel and sand, i.1997, Kennedy 00039C (AAS); Dronning Maud Land, Filchnerfjella, Rakenkniven, 1800 m, near snow petrel nest site, xii. 1996, R.I.L. Smith 10063 (AAS); Scotia Sector, Pensacola Mts., Pillow Knob, 812 m, exposed mountain ridge, ii. 1999, Convey 446A (AAS). Argentina: Tierra del Fuego, Ushuaia, Rio Lapataia, ii. 2001, Frödén 1793 (LD). Caloplaca soropelta (E. S. Hansen, Poelt & Søchting) Søchting Graphis Scripta 4: 35 (1992). C. citrina var. soropelta E. S. Hansen, Poelt & Søchting, Meddr. Grønland, Biosc. 25: 26; type: Greenland, Disko, Felsige Hänge NE der Arktischen Station Godhavn, Basalt, S-seitiges geschutzte Spalten eines Vogelfelsens, um 20 m, 9. viii. 1982, Poelt & Ullrich (GZU!-holotype). Thallus peltate to squamulose forming up to 2-cm-large crusts on moss or rock; squamules mostly regular, sometimes broadly lobed, up to 1.2 mm, initially often strongly convex, later flat or slightly concave, orange yellow, with margins often upward recurved. Soralia always present, lipshaped and confluent, developing at the lower side of the margins of the squamules exposing golden yellow soredia; rarely, a uniform sorediate crust may be formed; soredia 25–35 lm diam. (Fig. 4). Pycnidia not seen. See also description in Hansen et al. (1987) and Søchting (1992). Secondary chemistry All screened specimens have high concentrations of parietin and small proportions of teloschistin, fallacinal, parietinic acid and emodin corresponding to chemosyndrome A (Søchting 1997). Ecology Specimens from the Antarctic Continent grow on strongly convex moss cushions together with Xanthomendoza borealis and C. flava, often accompanied by C. darbishirei. In Tierra del Fuego and in the Northern Hemisphere, C. soropelta is a saxicolous species that prefers to grow in crevices where it anchors the squamules with hyphal strands. Distribution Caloplaca soropelta was described from Greenland (Hansen et al. 1987) and was later found in Svalbard (Søchting 1992) and Iceland (Kristinsson 1999); it has been recently reported from Antarctica, Victoria Land by Smykla et al. (2011). It is widely distributed in Antarctica, although it appears to be less abundant than C. darbishirei (Fig. 5). Two collections are known from southernmost Argentina, and one from southernmost Chile. The molecular data show it to belong to an exclusively Southern Hemisphere clade with several representatives in Antarctica, for example, C. hookeri, C. millegrana, C. regalis and C. sublobulata. These related species are 123 Fig. 5 Distribution map of C. soropelta among the most dominant lichens on Antarctic sea shores. No species from this clade, except C. soropelta, is known from the Northern Hemisphere. Selected specimens examined Antarctica: South Shetland Islands, Deception Isl., Fumarole area north of Mt. Pond, 500 m, on unheated yellowish tufa rock outcrops, immediately adjacent to fumaroles, i. 2002, R.I.L.Smith 11184 (AAS); Antarctic Peninsula, Hauberg Mountains, Ellsworth Land, Hauberg Mts., 650 m, Convey 628 (AAS); Victoria Land, Kar Plateau, i. 1992, Seppelt 19184 (HOB); Edmonson Point, North Valley, dry lava boulder, 25 m, xii. 1995, R.I.L.Smith 9589 (AAS); Granite Harbor, i. 2006, Bargagli A922 (TSB); Ingrid Christensen Land, Vestfold Hills, Mule Peninsula, 20 m, on sandy silt in gravel, ii. Polar Biol (2012) 35:1143–1149 1979, Seppelt 8922 (HOB); Rauer Islands, 10. xii. 1983, Cracknell (HOB); Mac. Robertson Land, West side of Mawson Rock, over moss cushions, i. 1974, Filson 14818 (AAS); Murray Monolith, i. 1979, Seppelt 8197 (HOB); Dronning Maud Land, Henriksenskjera, 1282 m, beside small drainage pond below southern knoll of ridge, xii. 1996, R.I.L. Smith 10074 (AAS). Argentina: Rio Turbida NE of Puerto Natales, 620 m, W-exposed overhang, Søchting 10421(C). - Chile: Region XII, Isla Navarino, 25 km WNW Pto Williams, 580 m, Crevices in overhang, i. 2005, Søchting 10387 (C); Parque Nacı́onal Torres del Paine. Walk from Lago Gray. MZS 59 (C). Iceland: S-Phingeyjarlasysla, Myvatn, 280–300 m, vertical lava by lake, Søchting 7536 (C). Acknowledgments Lene Christiansen performed the HPLC analyses, Lisbeth Knudsen assisted with molecular sequencing, and Bjørn Hermansen prepared the maps. Rod Seppelt, Hobart, Tasmania and Helen Peat, British Antarctic Survey, Cambridge, provided information and material from HOB and AAS, respectively. Leopoldo G. 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