Cryptogamie, Bryologie, 2009, 30 (2): 265-269 © 2009 Adac. Tous droits réservés Fossombronia caespitiformis De Not. ex Rabenh. subsp. multispira (Schiffn.) J.R. Bray et Cargill in Belgium, a remarkable extension of its European range André SOTIAUXa,b, Herman STIEPERAEREb*, Odette SOTIAUXc & Henri POHLd aUniversité bNational de Liège, Institut de Botanique, B22 Sart Tilman, B-4000 Liège. Botanic Garden of Belgium, Domein van Bouchout, B-1860 Meise cChaussée dPlace de Bruxelles 676, B-1410 Waterloo de Baileux 33, B-6464 Baileux (Received 10 September 2008, accepted 8 October 2008) Abstract – Fossombronia caespitiformis subsp. multispira has been found at Gozée (province of Hainaut, Belgium), 330 km outside its known range. This subspecies is characterised by elaters having 3-4 spirals. The plants from Gozée correspond well with the original description of Fossombronia husnotii, a synonym of this subspecies. As the rhizoids are purple, not colourless as those traditionally described for F. husnotii, rhizoid colour is not a reliable character to distinguish F. caespitiformis subsp. multispira. Résumé – Fossombronia caespitiformis subsp. multispira a été découvert à Gozée (province de Hainaut, Belgique), 330 km en dehors de son aire connue. Cette sous-espèce est caractérisée par des élatères à 3-4 spires. La morphologie du matériel belge correspond bien à la description originale du F. husnotii décrit par Corbière en 1904, un synonyme de cette sous-espèce. Comme les rhizoïdes sont pourpres, non hyalins comme ceux habituellement décrits pour F. husnotii, la couleur des rhizoïdes n’est pas un caractère fiable pour distinguer F. caespitiformis subsp. multispira. Fossombroniaceae / Fossombronia caespitiformis / Fossombronia husnotii / rhizoid colour / Belgium INTRODUCTION In the recent checklist of Belgian bryophytes (Sotiaux et al., 2007) several species have been added to the list. This was mainly due to intensive prospecting in Southern Belgium. Two species considered extinct were rediscovered, Philonotis marchica (Hedw.) Brid. and Pterygoneurum lamellatum (Lindb.) Jur., * Correspondence and reprints : Stieperaere@br.fgov.be 266 A. Sotiaux, H. Stieperaere, O. Sotiaux & H. Pohl both not seen for nearly a century. One of the species that still remained on the ‘hit list’ was Fossombronia caespitiformis De Not. ex Rabenh., found once in 1903 between Lives and Bossimé (Prov. Namur) in the Belgian district of the Meuse (Mansion, 1905). This find has been much debated. Düll (1983) listed this species for Belgium and indicated that he had seen material. However, the only specimen is (now) sterile and even lacks perianths. De Zuttere & Schumacker (1984) did therefore not accept the presence of this submediterranean species in their checklist and it remained absent from the subsequent checklists and in the flora of Siebel & During (2006). Nevertheless Schumacker & Vá≈a (2005) follow Düll (1983) and list F. caespitiformis for Be, the abbreviation for the geographical territories of both Belgium and the Grand Duchy of Luxembourg. When in June 2008 A.S. studied a Fossombronia specimen he just had collected, with O.S. & H.P, on the side of a ditch between a wheat field and a forest near Gozée (Prov. Hainaut, Belgium), he found the characteristic spores of F. caespitiformis. However, spore diameter of the recent collection (32-35 µm) was much lower than that of typical F. caespitiformis. We decided therefore to study the specimen in more detail. MORPHOLOGY AND ECOLOGY OF THE BELGIAN SPECIMEN Gametophyte resembling F. pusilla (L.) Nees, rhizoids violet. Spores well developed, (30.3) 32-35 (37.4) µm in diameter, distally densely covered with 4-6 µm long truncate, flattened spines, broadened at the base to form a star like pattern, some spines confluent at their base but not forming short lamellae pattern (Figs 1-3); spores proximally without a clear triradiate mark, covered with low, irregular alveolae (Fig. 4). Elaters with 3 (4) spirals, exceptionally bispiralled. Belgium, province of Hainaut, Gozée, 50°19’37”N 4°21’11”E; IFBL/ H4.25.23, UTM/ ER9676, alt. 185 m, 26-06-2008, leg A. Sotiaux n° 36.552 (herb. Sotiaux) Gozée is situated in the Mosan district, a loam plateau often overlying calcareous deposits that are exposed in deep valleys. The locality near the artificial lake of the Grand Vivier forms part of the pure loam plateau devoted largely to agriculture. The north side of the drain where F.caespitiformis was found had a varied flora. Next to the Fossombronia plants grew large colonies of Phaeoceros carolinianus (Michx.) Prosk. with Riccia glauca L., Amblystegium serpens (Hedw.) Schimp., Barbula unguiculata Hedw., Bryum violaceum Crundw. et Nyholm, Dicranella schreberiana (Hedw.) Dixon, D. staphylina H.Whitehouse, Phascum cuspidatum Hedw., Physcomitrium pyriforme (Hedw.) Bruch et Schimp., Pohlia melanodon (Brid.) A.J.Shaw and Tortula truncata (Hedw.) Mitt. DISCUSSION Fossombronia caespitiformis is a very variable taxon. Stotler et al. (2003) distinguish two subspecies: F. caespitiformis subsp. caespitiformis and F. caespitiformis subsp. multispira (Schiffn.) J.R.Bray et D.C.Cargill. The only diagnostic character given for F. caespitiformis subsp. multispira is that the elaters Fossombronia caespitiformis in Belgium 267 Figs 1-4. Fossombronia caespitiformis subsp. multispira, SEM-micrographs of spores (from Sotiaux 36552). 1-3. Distal view. 4. Proximal view. are consistently 3-5 spiralled, rarely bispiralled, whereas in subsp. caespitiformis they are consistently bispiraled, rarely trispiraled centrally. They also reduce F. husnotii Corb. to synonymy of F. caespitiformis subsp. multispira. Corbière (1889) distinguished his F. husnotii from F. caespitiformis on spore characters (spores with lamellae elevated at the intersection of the vague and incomplete alveolae; creating a star like pattern on the surface) and on the 3-4 spiralled elaters. He did not mention rhizoid colour. He eventually reduced F. husnotii to F. caespitiformis var. husnotii (Corb.) Corb. because of the many overlaps in the spore characters of both taxa (Corbière, 1904). Spore diameter is much lower than the figures for F. caespitiformis spores given in Paton (1999) and Schumacker & Vá≈a (2005): 38-56(64) µm, rarely 30-40 µm, resp. 42-65 µm, especially since Paton (1999) states that the small spored form has spines and tubercles largely reduced to conical papilla. The spore diameter of F. husnotii given in Corbière (1889) is only ca. 40 µm compared to 45-50 µm for F. caespitiformis. Also, in his original description of F. caespitiformis 268 A. Sotiaux, H. Stieperaere, O. Sotiaux & H. Pohl var. multispira Schiffner (1918†1) indicates that the spores are smaller than those of the type variety “Differt a typo sporis minoribus, …”. The 3(4)-spiralled elaters, and the smaller spore diameter of the Belgian collection compared to typical F. caespitiformis var. caespitiformis makes us confident that this is F. caespitiformis subsp. multispira. Also, spore ornamentation of this collection matches very well the description and plate of its synonym F. husnotii (Corbière, 1889). Since Müller (1909), European authors (e.g. Paton, 1999) have stressed the colourless or pale brown rhizoids and the variable spores of F. husnotii with irregular truncate papillae, sometimes united to irregular lamellae or irregular alveolae on the distal face. Thus, Schumacker & Vá≈a (2005) who follow the nomenclature of Stotler et al. (2003) and Stotler & Crandall-Stotler (2007), still key out F. caespitiformis subsp. multispira on the colourless to pale brown rhizoids and variable spore ornamentation and do not mention the number of spirals in the elaters. Stotler et al. (2003) and Stotler & Crandall-Stotler (2007), however, do not mention rhizoid colour, only the number of spirals in the elaters. As our find shows, rhizoid colour is not a reliable character to distinguish F. caespitiformis var. multispira. In fact, the rhizoids of two Dutch Fossombronia wondraczekii collections were consistently brown to colourless (During in Gradstein & van Melick, 1996). Fossombronia taxa with variable rhizoid pigmentation between populations and even on individual plants have been described from Australia (e.g. F. scrobiculata G.A.M.Scott & D.C.Pike and F. vermiculata G.A.M.Scott & D.C.Pike; Scott & Pike, 1984) and from South Africa (F. cederbergensis Perold; Perold, 1998). The habitat at Gozée is rather nondescript and typical of intensive arable fields. Mansion (1905) found F. caespitiformis in a calcareous field in Bossime, between Live and Erpent, 4 km SE of Namur, Prov of Namur, in the Mosan district, in the company of Fossombronia pusilla, Riccia glauca, Anthoceros agrestis Paton and Phaeoceros laevis (L.) Prosk. It is therefore difficult to understand why F. caespitiformis s.l. is so rare. Hill et al. (1991) also can not easily explain the scarcity of this species in England in terms of its habitat requirements, but think this may reflect that it is at its climatic limit. Mansion (1905) wrote that his specimens were abundantly fertile; the specimen at BR is sterile. Until another fertile specimen is found, this recent find definitely documents F. caespitiformis s.l. for Belgium but makes the find of Mansion more plausible. Both subspecies of F. caespitiformis are present in nearly all the Mediterranean countries (Ros et al., 2007) and in Madeira and the Canaries. Along the Atlantic coast it is rare from Portugal to France up to the English Channel and in Southern England (Hill et al., 1991). Fossombronia caespitiformis subsp. caespitiformis is also present in Australia (McCarthy, 2006). The nearest localities to Gozée are in Normandy (Villons-les-Buissons, at 365 km; Lecointe, 1978) and in Southern England (at ca. 330 km; Hill et al., 1991). 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