After examination of specimens in the herbarium of the Botanic Garden and Botanical Museum Berlin, eight species of smut fungi are reported for the first time from Greece: Microbotryum dianthorum on Dianthus viscidus, Sporisorium pulverulentum on Saccharum strictum, Tilletia fusca on Vulpia ciliata, T. lolii on Lolium temulentum, Urocystis dactylidina on Dactylis glomerata subsp. hackelii, U. johansonii on Juncus bufonius, U. ornithogali on Ornithogalum sp. and U. ulei on Festuca jeanpertii. Four species of smut fungi are recorded on new host plants making new fungus-host combinations: Microbotryum dianthorum on Dianthus viscidus, Tranzscheliella williamsii on Stipa isoldeae, Urocystis dactylidina on Dactylis glomerata subsp. hackelii and U. ulei on Festuca jeanpertii. Two plant species are reported as new hosts of smut fungi already known from Greece: Stipa isoldeae for Tranzscheliella williamsii, and Lygeum spartum for T. hypodytes. All ten species of smut fungi are illustrated. A description is also provided for Urocystis agropyri, recorded in Greece on Thinopyrum junceum.
Version of record first published online on 28 July 2016 ahead of inclusion in August 2016 issue.
Introduction
Greece is home to an unusually high diversity of vascular plants, ranking among the highest in Europe and the Mediterranean area with 5752 species, and one of the most important centres of endemism with 1278 endemic species (22.2 % of the total number of species) (Dimopoulos & al. 2013). This is a prerequisite for a high species richness of parasitic fungi on plants. However, the diversity of the smut fungi in Greece (Ustilaginomycotina and Microbotryales) is not intensively studied. No regional monographic study has been carried out yet. To date, only 66 species on 77 vascular plant species have been reported, making 86 smut-host combinations (Hohenbühel 1868; Bornmüller 1894, 1928; Magnus 1894; Maire 1905, 1917; Sarejanni 1935, 1939; Sydow 1935; Săvulescu 1937; Konstantinia-Sulidu 1939; Maire & Politis 1940; Petrak 1943, 1944, 1956; Apostolides 1952; Critopoulos 1953; Demetriades & Zachos 1962; Durrieu 1968; Brandenburger 1969; Pyrowolakis & Weltzien 1970; Vánky 1980, 1985b, 1986, 1989, 1990a, b, 1991, 1992, 1996, 1998, 2003a, b, 2008, 2011; Scholz & Scholz 1988; Scheuer 1992, 2010; Vánky & Oberwinkler 1994; Denchev 1997; Triebel 1998, 1999; Vánky & Scholz 2001; Vánky & Berner 2003; Kashefi & Vánky 2004; Vánky & al. 2005; Denchev & Minter 2008, 2011a, b; Braun 2013; Denchev & al. 2013; Savchenko & al. 2014).
In the present article, eight species of smut fungi (indicated by * in the text) are reported for the first time from Greece: Microbotryum dianthorum, Sporisorium pulverulentum, Tilletia fusca, T. lolii, Urocystis dactylidina, U. johansonii, U. ornithogali and U. ulei. Four fungushost combinations are recorded for the first time: Microbotryum dianthorum on Dianthus viscidus, Tranzscheliella williamsii on Stipa isoldeae, Urocystis dactylidina on Dactylis glomerata subsp. hackelii and Urocystis ulei on Festuca jeanpertii. Two plant species are reported as new hosts of smut fungi already known from Greece: Stipa isoldeae for Tranzscheliella williamsii and Lygeum spartum for T. hypodytes.
The smut fungi reported here were found during examination of specimens in the herbarium of the Botanic Garden and Botanical Museum Berlin.
Material and methods
Dried specimens from the herbarium of B (herbarium code according to Thiers 2016+) were examined under a light microscope (LM) and a scanning electron microscope (SEM). For LM observations and measurements, spores were mounted in lactoglycerol solution (w : la : g1 = 1:1:2) on glass slides, gently heated to boiling point to rehydrate the spores, and then cooled. The measurements of spores are given as min-max (mean ± 1 standard deviation). For SEM, spores were attached to specimen holders by double-sided adhesive tape and coated with platinum-palladium in an ion sputter. The surface structure of the spores was observed and photographed at 5 kV accelerating voltage using a JEOL JSM7600F scanning electron microscope (Naturalis Biodiversity Center, Leiden, The Netherlands). The descriptions below are based entirely on the specimens examined. The description of spore ornamentation is in accordance with Denchev & al. (2013). The height of the wall ornamentation (warts and spines) was measured with SEM. Lists of shapes of sterile cells or spores are arranged in decsending order of frequency.
New records of smut fungi for Greece
*Microbotryum dianthorum (Liro) H. Scholz & I. Scholz in Englera 8: 206. 1988, s. lat. — Fig. 1A–C.
Sori in anthers (some flowers may be unaffected). Spore mass dark reddish brown. Spores globose, subglobose, broadly ellipsoidal, ellipsoidal or ovoid, (5.5-) 6-8.5(-9.5) × (5-)5.5-7.5(-8) (7.2 ± 0.6 × 6.4 ± 0.5) µm (n = 100), pale vinaceous; spore wall reticulate, 1–1.5 µm thick; meshes (5-)6-9 per spore diameter, polygonal or rounded, 0.4-1(-1.8) µm wide; muri 0.5–0.9 µm high; interspaces in SEM smooth or rugulose.
Specimen examined — On Dianthus viscidus Bory & Chaub. — Greece: Sterea Ellas, Prov. Etolia Akarnania, Panatolikos massif, 1450–1550 m, 30 Jun 1982, H. Scholz (B 70 0007639).
Note — Dianthus viscidus is a new host for Microbotryum dianthorum.
*Sporisorium pulverulentum (Cooke & Massee) Vánky in Symb. Bot. Upsal. 24(2): 120. 1985. — Fig. 1D–F.
Sori in all spikelets of inflorescence, elongate to cylindric, c. 1.5 × 0.7 mm, partially concealed by glumes, covered by a thick yellow-brown to rusty brown peridium that ruptures irregularly (usually at apex) exposing a single, stout, tapering, sometimes slightly branched columella with shallow, longitudinal furrows. Columella to 5 mm long, surrounded by powdery, blackish brown mass of spores and sterile cells. Sterile cells in irregular groups (single sterile cells not seen), subglobose, broadly ellipsoidal or irregular, often collapsed, (7-)8.5-16.5(-18.5) µm long, hyaline; cell wall 0.6–1.2 µm thick, smooth. Spores subglobose, broadly ellipsoidal, slightly irregular or ovoid, sometimes ellipsoidal, (9.5-)10-13.5(-15) × (8.5-)9.5-12(-13) (12.0 ± 0.8 × 10.8 ± 0.8) µm (n = 100), medium yellow-brown; spore wall ± evenly thickened, 0.6-0.8(-1) µm thick, often with one or two paler, rounded areas of 2.5–4 µm in diam., minutely verruculose, spore profile not affected or slightly affected, in SEM minutely echinulate; spinules to 0.2 µm high, spore surface densely punctate between spinules.
Specimen examined — On Saccharum strictum (Host) Spreng. — Greece: Rodos island, c. 1 km E of Archangelos, 23 Oct 2003, M. Ristow (B 70 0015526).
Note — Sporisorium pulverulentum is a rare species known only from S Europe and S and SE Asia (India, Malaysia and Indonesia) (Vánky 2011; Chalkley 2015). In Europe, it has previously been recorded only from Serbia (Mt Fruška Gora near Novi Sad; Vánky 1985a, b).
*Tilletia fusca Ellis & Everh. in J. Mycol. 3: 55. 1887. — Fig. 2A–C.
Sori in ovaries of most spikelets of infected plant, ovoid, 1.5–2.2 mm long, partially concealed by floral envelopes, initially covered by thin, dark brown pericarp that later ruptures exposing powdery, dark reddish brown mass of spores and sterile cells. Sterile cells subglobose or broadly ellipsoidal, sometimes slightly irregular, (9.5-)10.5-14.5(-15.5) × (9-)10-13.5(-14.5) µm, hyaline; cell wall 0.9–1.6 µm thick, in SEM smooth. Spores globose, subglobose or broadly ellipsoidal, (16.5-)17.5-20.5(-21.5) × (16-)17-19.5 (-20.5) (19.1 ± 1.0 × 18.2 ± 1.0) µm (n = 100), light to medium yellow-brown, completely reticulate; spore wall 3–3.8 µm thick (including reticulum and hardly visible, 0.5–0.7 µm-thick inner layer); meshes (5-)6-8(-9) per spore diameter, usually polyhedral, sometimes rounded, (0.9-)1.2-3.5(-4) µm wide; muri 21–29 on equatorial circumference, in optical median view subacute or blunt, (1.2-)1.4-1.8(-2.2) µm high, in SEM some meshes with a low hemispherical protuberance on bottom.
Specimen examined — On Vulpia ciliata Dumort. – Greece: Crete, Agia Triada, 27 Mar 1979, R. Böcker (B 70 0015527).
*Tilletia lolii Auersw. ex G. Winter, Rabenh. Krypt.-Fl., ed. 2, 1(1): 109. 1881. — Fig. 2D–F.
Sori in all ovaries of infected plant, ovoid, 3-4 × 1.2-1.8 mm, partially concealed by floral envelopes, initially covered by thin, purplish brown pericarp that later ruptures exposing powdery, cinnamon-brown mass of spores and sterile cells. Sterile cells subglobose, broadly ellipsoidal or slightly irregular, (11.5-) 12.5-15.5(-18) × (10.5-)11.5-14.5(-16.5) µm, subhyaline; cell wall (0.9-)1.2-1.8(-2.3) µm thick, smooth. Spores globose, broadly ellipsoidal or subglobose, (18-)18.5-21.5(-23) × (17.5-)18-20(-21) (19.9 ± 0.7 × 19.0 ± 0.6) µm (n = 100), light yellow-brown, completely reticulate; spore wall 2.9–4 µm thick (including reticulum and 0.5–0.8 µm-thick inner layer), covered by a hyaline sheath 0.3–0.6 µm thick; meshes (5-)6-7(-8) per spore diameter, usually polyhedral, sometimes rounded, 0.7-3.8(-4.3) µm wide; muri 25–33 on equatorial circumference, in optical median view acute or subacute, 1.3-2.2(-2.5) µm high, in SEM single meshes with a low hemispherical or conical protuberance on bottom.
Specimen examined — On Lolium temulentum L. — Greece: Crete, Prov. Rethymno, between the mountain peaks Tsilivdikas and Xilis Korifi near Kali Sikia village, 720 m, 30 May 1983, Greuter & Matthäs (B 70 0015546).
Tranzscheliella hypodytes (Schltdl.) Vánky & McKenzie, Smut Fungi New Zealand: 156. 2002, s. lat. — Fig. 3A–C.
Sori around upper internode or around branches of aborted inflorescence, initially covered by upper leaf sheath or spatheole, respectively, later exposed; peridium absent. Spore mass powdery, blackish brown. Infection systemic. Spores subglobose, globose, broadly ellipsoidal or ovoid, 4-6(-6.5) × 3.5-5.5 (5.0 ± 0.4 × 4.4 ± 0.4) µm (n = 100), medium olivaceous brown; spore wall 0.5–0.7 µm thick, smooth or nearly so, often with small, hardly distinguishable hyaline caps at poles, in SEM minutely verruculose; warts flattened, often connected in small irregular groups; surface between main ornaments punctate.
Specimen examined — On Lygeum spartum Loefl. ex L. — Greece: Crete, near Ferma, 16 Apr 1994, H. Scholz & I. Scholz (as Ustilago hypodytes (Schltdl.) Fr., B).
Note — From Greece, Tranzscheliella hypodytes is known only on Achnatherum miliaceum (L.) P. Beauv. (Maire 1917, as Ustilago athenae Maire). Lygeum spartum is recorded here as a new host plant of T. hypodytes for Greece. There is a second species of Tranzscheliella on L. spartum, T. sparti (Massenot) Vánky, but its sori are restricted to the inflorescence and the spores are larger (6–8 µm long). The sori and spores of the Greek specimen reported here correspond to that of T. hypodytes s. lat.
Tranzscheliella williamsii (Griffiths) Dingley & Versluys in New Zealand J. Bot. 15: 477. 1977. — Fig. 3D–F; Fig. 4A.
Sori around upper internodes or aborted inflorescence branches, initially covered by upper leaf sheaths, later exposed. Spore mass powdery, blackish brown. Infection systemic. Spores slightly flattened, in plane view suborbicular, orbicular or broadly elliptic, sometimes slightly irregular, in plane view (5.5-)6-9(-9.5) × (5-) 5.5-7.5(-8) (7.4 ± 0.8 × 6.8 ± 0.5) µm (n = 100), medium olivaceous brown; spore wall 0.6–1 µm thick, smooth; exospore often cracked, bearing 2 persistent appendages on flattened sides, in SEM with low, flattened, densely packed ornaments connected in small groups and short rows or forming labyrinthiform pattern.
Specimen examined — On Stipa isoldeae H. Scholz. — Greece: Nomos and Eparchia Grevena, Vourinos massif, E of Exharos, 1150 m, serpentinite rocks, 16 Aug 1983, I. Hagemann, H. Ketelhut & H.-J. Wolf 962a, comm. H. Scholz (as Ustilago williamsii (Griffiths) Lavrov, B).
Notes — From Greece, Tranzscheliella williamsii has been previously recorded only once, as T. otophora Lavrov, on Stipa sp. (Petrak 1956). The relevant specimen is kept at the Mycological Collection of the Natural History Museum, Vienna (W): Epirus, Distr. Ioanina, Montes Pindus, in monte Tsuka Rossa ditionis pagi Vovousa (Viosa), 1600–1980 m, in pinetis, substr. serpent., 1–2 Aug 1956, K. H. Rechinger 18586 (K. H. Rechinger, Iter Graecum VIII, 1956; W 1976-04903) (Fig. 3D). This specimen was re-examined by us and its identification was confirmed.
Stipa isoldeae is endemic to Greece. This grass is reported here as a new host of Tranzscheliella williamsii.
Urocystis agropyri (Preuss) A. A. Fisch. Waldh. in Bull. Soc. Imp. Naturalistes Moscou 40: 258. 1867.
Sori in leaves, sheaths and culms as long striae, initially covered by epidermis that later ruptures disclosing semi-agglutinated, blackish brown mass of spore balls. Spore balls irregular, subglobose, broadly ellipsoidal, ellipsoidal or ovoid, composed of 1–4(or 5) central spores (1 = 26.5 %, 2 = 43.4 %, 3 = 20.3 %, 4 = 7.3 %, 5 = 2.4 %; n = 875), surrounded by a continuous or almost continuous layer of sterile cells, (16.5-)18-26(-28.5) × (14.5-)16-20(-21.5) µm [with 1 spore], (20.5-) 22.5-29(-33) × (17.5-)19-24.5(-26.5) µm [with 2 spores], (24-)25.5-33(-36) × (19-)21-26.5(-28.5) µm [with 3 spores], (27.5-)29-40(-44.5) × (22.5-)24-29 (-31.5) µm [with 4 spores]. Sterile cells elliptic, irregular, suborbicular, broadly elliptic, elongate or ovate in outline, collapsed, 4.5-12(-13) µm long, light yellow-brown; cell wall on side distal to spores 0.6–1.1 µm thick, on side proximal to spores thicker, smooth, in SEM punctate; projections irregularly arranged, often fused. Spores broadly ellipsoidal, subpolyhedral, subglobose, ellipsoidal or ovoid, sometimes cuneate or elongate, often slightly flattened on a few places, (11.5-)12.5-17.5(-19.5) × (10-)10.5-14.5(-16) (15.8 ±1.4 × 12.8 ± 1.2) µm (n = 100), medium reddish brown; spore wall slightly uneven, 0.7–1.1 µm thick.
Specimen examined — On Thinopyrum junceum (L.) Á. Löve (= Elymus farctus (Viv.) Runemark ex Melderis). - Greece: Kos island, Marmari, 1 May 1990, H. Scholz & I. Scholz (B).
Note — In some websites, Urocystis agropyri is reported from Greece as collected on wheat. In fact, the correct name of the smut fungus in leaves and stems of Triticum is U. tritici Körn. The only other known record of U. agropyri from Greece is on Thinopyrum junceum (as Elymus farctus) from Kos island (collected on 21 Apr 1990, H. Scholz & I. Scholz, Vánky, Ustilaginales exsiccata, no. 769, Vánky 1990b). Urocystis agropyri in its broad sense represents a species complex (Vánky 2011) that probably contains a few species. For clarification of their number and specialization and whether these species are morphologically recognizable, this complex needs a combined molecular and morphological study. For this reason, we considered that it would be helpful to include here a description of the Greek specimen examined by us on Thinopyrum junceum.
*Urocystis dactylidina (Lavrov) Zundel in Contr. Dept. Bot. School Agric. Pennsylvania State Coll. 176: 314. 1953,—Fig. 4B,C.
Sori in leaves and sheaths as long striae, initially covered by epidermis that later ruptures disclosing powdery, blackish brown mass of spore balls. Spore balls irregular, broadly ellipsoidal, subglobose or ovoid, composed of 1–3(or 4) central spores (1 = 42.5%, 2 = 45.3 %, 3 = 9.7%, 4 = 2.5 %; n = 746), surrounded by a continuous or almost continuous layer of sterile cells, (18-)20-29(-32) × (16-)17-24(-28) µm [with 1 spore], (24-)26-34(-37) × (18-)20-28(-32) µm [with 2 spores], (29-)31-38(-42) × (23.5-)25-33(-37) µm [with 3 spores]. Sterile cells suborbicular, broadly elliptic, irregular, elliptic or ovate in outline, often collapsed, (4.5-)5.5-14(-17) µm long, medium yellow-brown; cell wall irregularly thickened, on side distal to spores 0.7-2.3(-2.6) µm thick, on side proximal to spores thicker, smooth, in SEM punctate; projections sometimes connected, forming fine, irregular pattern. Spores subpolyhedral, broadly ellipsoidal, subglobose or ovoid, sometimes ellipsoidal or cuneate, sometimes slightly flattened on a few places, (11.5-) 12.5-18.5(-20) × (10-)11-15.5(16.5) (15.3 ± 1.5 × 13.1 ± 1.2) µm (n = 100), medium reddish brown; spore wall slightly uneven, 0.8-1.2(-1.4) µm thick.
Specimen examined — On Dactylis glomerata subsp. hackelii (Asch. & Graebn.) Cif. & Giacom. — Greece: Dodecanesus, Insula Karpathos, in Insula Mira (Moira), infra pagum Epano Afiartis sita, 35°27′N, 27°11′10″E, 10–40 m, 17 May 1983, W. Greuter & R. Pleger, Plantae Austro-Aegaeae 19738, det. H. Scholz (B).
Note — Urocystis dactylidina is a rare species collected only a few times in C Europe (Czech Republic, Switzerland, ?Poland) and Asia (W and E Siberia) (Vánky 1985a, 1994, 2011; Azbukina & Karatygin 1995; Karatygin 2012). Vánky (2011) noted that the host plant identity of all collections, seen by him, was suspected to be wrongly identified. For this reason, U. dactylidina needs a purposeful investigation. Dactylis glomerata subsp. hackelii, reported here, is a new host of U. dactylidina.
*Urocystis johansonii (Lagerh.) Magnus in Verh. Bot. Vereins Prov. Brandenburg 37: 94. 1896. — Fig. 4D–F.
Sori at basal part of leaves as bulb-like swellings, initially covered by epidermis that later ruptures disclosing powdery, blackish brown mass of spore balls. Spore balls subglobose, irregular, broadly ellipsoidal, ovoid or ellipsoidal, composed of 1-5(-9) central spores (1 = 6 %, 2 = 29.6 %, 3 = 35.2 %, 4 = 15.6 %, 5 = 8.8 %, 6 = 2.8 %, 7 = 1 %, 8 = 0.7 %, 9 = 0.3 %; n = 609), surrounded by a continuous layer of sterile cells, (13.5-) 14.5-20(-21) × (12.5-)13.5-17.5(-18.5) µm [with 1 spore], (18-) 20-26(-29) × (14-)16-20(-22) µm [with 2 spores], (21-)22-30(-31.5) × (18-)19-23(-24.5) µm [with 3 spores], (23.5-)25-33(-35) × (19.5-)21-26(-28.5) µm [with4 spores], (27-)29-41(-45) × (20-)22-31(-33) µm [with 5 spores]. Sterile cells irregular, suborbicular, broadly elliptic or ovate in outline, collapsed, 3.5-13(-15) µm long, light or medium yellow-brown; cell wall on side distal to spores 0.5–0.8 µm thick, on side proximal to spores thicker, smooth, in SEM smooth. Spores subglobose, broadly ellipsoidal, slightly irregular, ellipsoidal or ovoid, sometimes slightly flattened on a few places, 10.5-15(-16) × (8-)9-12(-13) (13.0 ± 1.0 × 10.7 ± 0.8) µm (n = 100), dark reddish brown; spore wall slightly uneven, 0.9—1.4(—1.6) µm thick.
Specimen examined— On Juncus bufonius L. — Greece: Crete, [Prov. Iraklio], between Kasteli and Karouzana, 17 Apr 1994, H. Scholz & I. Scholz (B).
*Urocystis ornithogali Körn. ex A. A. Fisch. Waldh., Aperçu Syst. Ustilag.: 41. 1877. — Fig. 5A–C.
Sori in leaves and stems as small to large pustules, initially covered by epidermis that later ruptures disclosing powdery, blackish brown mass of spore balls. Spore balls irregular, broadly ellipsoidal, subglobose or ovoid, composed of 1-3(-5) central spores (1 = 31%, 2 = 41.7 %, 3 = 21.1 %, 4 = 5.3 %, 5 = 0.9 %; n = 546), surrounded by a continuous layer of sterile cells, (18-)20-26(-28) × (16.5-)18-23(-25.5) µm [with 1 spore], (22-)25-33(-35) × (19.5-)21-26(-28) µm [with 2 spores], (24.5-)27-40(-44) × (22.5-)25-32(-35) µm [with 3 spores]. Sterile cells irregular, suborbicular, orbicular or ovate in outline, collapsed, 5-13(-15) µm long, light or medium yellow-brown; cell wall on side distal to spores 0.4–0.8 µm thick, on side proximal to spores thicker, smooth, in SEM smooth to sparcely punctate. Spores subpolyhedral, broadly ellipsoidal, subglobose or cuneate, sometimes slightly flattened on a few places, (13-)14.5-20.5(-22.5) × ( 10.5-)11.5-16(-17) (17.3 ± 1.4 × 14.2 ± 1.0) µm (n = 100), medium reddish brown; spore wall slightly uneven, 0.7–1 µm thick.
Specimen examined — On Ornithogalum sp. — Greece: Euböa [Evvia], E of Eretria, near hotel Miramare, 19 Mar 1991, H. Scholz & I. Scholz (B).
*Urocystis ulei Magnus in Rabenhorst, Fungi Europ. exsicc. 17: no. 2390. 1878. — Fig. 5D–F.
Sori in leaves and sheaths (infected plants usually sterile) as long, slightly swollen striae, initially covered by epidermis that later ruptures disclosing powdery, blackish brown mass of spore balls. Spore balls subglobose, broadly ellipsoidal, irregular, ellipsoidal or ovoid, composed of 1 or 2(-4) central spores (1 = 78.4%, 2 = 16.6 %, 3 = 4.2 %, 4 = 0.8 %; n = 529), surrounded by a continuous or almost continuous layer of sterile cells, (14.5-)16-27(-29) × (12-)13.5-22(-23.5) µm [with 1 spore], (17.5-)20-34(-38) × (14.5-)16-25(-27) µm [with 2 spores], (27-)29-37(-40) × (22-)24-32 (-35) µm [with 3 spores]. Sterile cells suborbicular, orbicular, irregular, broadly elliptic, elliptic or ovate in outline, collapsed, (5-)6-13(-15) µm long, light or medium yellow-brown; cell wall on side distal to spores 0.5–0.7 µm thick, on side proximal to spores thicker, smooth, in SEM punctate. Spores subglobose, broadly ellipsoidal, subpolyhedral, slightly irregular, ellipsoidal or ovoid, sometimes elongate, sometimes slightly flattened on a few places, (11.5—)13—17(—19.5) × (10-)11-14.5(-15.5) (14.8 ± 1.4 × 12.7 ± 1.2) µm (n = 100), medium reddish brown; spore wall slightly uneven, 0.8–1.5 µm thick.
Specimen examined — On Festuca jeanpertii (St.-Yves) Markgr. — Greece: Sterea Ellas, Prov. Fokis, Vardousia massif, S of Kato Mousounitsa, 1600 m, 27 Jun 1982, H. Scholz (B).
Note — Festuca jeanpertii is a new host for Urocystis ulei.
Acknowledgements
This research received support from the SYNTHESYS Project ( http://www.synthesys.info/), which is financed by European Community Research Infrastructure Action under the FP7 “Capacities” Program (grants no. DE-TAF-4056 to C. M. Denchev, and NL-TAF-4973 to T. T. Denchev). The assistance of Dr Harrie J. M. Sipman (Botanic Garden and Botanical Museum Berlin) and Bertie-Joan van Heuven (SEM lab of Naturalis Biodiversity Center, Leiden, The Netherlands) is kindly acknowledged. We also thank Kálmán Vánky and an anonymous reviewer for their comments on an earlier version of this paper.