Y. Krippel The Hymenophyllaceae (Pteridophyta) in Luxembourg. Past, present and future The Hymenophyllaceae (Pteridophyta) in Luxembourg. Past, present and future Yves KRIPPEL Research associate of the Luxembourg National Museum of Natural History 18A, rue de Rollingen, L-7475 Schoos [email protected]@mnhn.lu Keywords: Hymenophyllum tunbrigense, Trichomanes speciosum, Luxembourg, Petite Suisse Introduction Luxembourg, and in particular the 'Petite Suisse' sandstone region, is one of the few continental areas ever known for Hymenophyllum tunbrigense (L.) Smith, a species that generally occurs in a more Atlantic range (Jalas & Suominen 1972). The Tunbridge fi lmy-fern was fi rst discovered in this continental island in 1823, but the location of the major colonies remained uncertain until the early 20th century following its re-discovery in 1873. In 1993 the gametophytes of another fi lmy-fern, the Killarney fern (Trichomanes speciosum Willd.), were fi rst discovered for continental Europe in the same region. Investigations showed however, that Fig. 1: Patch of Hymenophyllum tunbrigense (Tunbridge unlike Hymenophyllum tunbrigense, the gameto- Filmy-fern) with leaves in good condition, near Berdorf phytes of Trichomanes speciosum are quite common (Luxembourg). Photo: Y. Krippel. in the 'Petite Suisse' area, as well as on Devonian schist in the Luxembourg Ardennes region. sites were found in the 'Petite Suisse', but the long-awaited discovery in the German part of the Luxembourg sandstone area waswas only made in Tunbridge Filmy-fern 1963 (Nieschalk 1964). WithinWithin continental Europe the TTunbridgeunbridge Filmy-fern wwasas also found in the (Hymenophyllum tunbrigense) Elbsandsteingebirge (sites unfortunately extinct) and in the French Vosges (Jalas & Suominen 1972). Nowadays the populations of Hymenophyllum tunbrigense havehave seriously suff ered and many sites History of its discovery are extinct in the region, as wwellell as in other parts of Europe. Hymenophyllum tunbrigense (Fig. 1) was fi rst discovered in Luxembourg - and so within conti- nental Europe - by the Belgium Botanist B.C. Du Mortier on a botanical trip with his friend P. Michel Distribution and status in 1823 [1821 as o� en mentioned in literature is not correct (Reichling 2005)]. At that time however The 'Petite Suisse' area in Luxembourg is one of nobody seemed very impressed by the discovery the few continental areas ever known for Hymen- of that Atlantic species in this continental island. ophyllum tunbrigense. Due to environmental Half a century passed, and it was in 1873, that J.- changes and external pressures (specimen collec- P. J. Koltz rediscovered the plant near Berdorf in tions, tourism and outdoor activities, …) a certain the valley of the Roitzbach (Koltz 1873). A� er the amount of sites have disappeared in the last fi rst discoveries in Luxembourg, numerous inves- decades (Fig. 2). Recent surveys have now shown tigations were made in the region and several a certain population increase. Ferrantia • 44 / 2005 209 Y. Krippel The Hymenophyllaceae (Pteridophyta) in Luxembourg. Past, present and future Fig. 2: Distribution map of Hymenophyllum tunbrigense (yellow squares: extinct sites, red squares: still existing sites). Grid: Gauss-Luxembourg, square kilometres. 210 Ferrantia • 44 / 2005 Y. Krippel The Hymenophyllaceae (Pteridophyta) in Luxembourg. Past, present and future An initial survey, realised in 1988, revealed the existence of 240 patches of fi lmy-fern which are Killarney Fern sca� ered amongst 27 sites. Their distribution shows a cluster of 5 major rock complexes which (Trichomanes speciosum) are situated circa one kilometre apart. A total of 20849 leaves covering a surface area estimated at 11.88 m2 were identifi ed. Of these, only 40% were considered to be in good conditions and the History of its discovery majority of the population comprised either dead or dying leaves, with only one of the colonies containing a few fertile leaves. (Schwenninger Although primarily a species of the UK, Ireland, 1988). Bri� any and the Atlantic Islands (Canaries, Madeira and Azores), the fi lmy-fern Trichomanes A new survey carried out in 2000 has shown that the number of fi lmy-fern patches has increased to speciosum (Killarney fern) is also found in Europe 360 and the entire population now spreads over at sca� ered locations in other parts of France, a surface area estimated at 12.38 m2, consisting of Spain, Portugal and Italy (Jalas & Suominen 1972). some 74700 leaves of which 74% are considered The gametophytic generation of Trichomanes to be in good condition. Fertile leaves totalled 212 speciosum can however be found independently and were encountered in most sites. For the fi rst time, fi lmy-fern gametophytes and young sporo- of the sporophyte and seems to be widespread phytes were identifi ed, thereby confi rming that it is in Europe, in contrast to the sporophyte (Rumsey capable of reproducing both by vegetative spread et al. 1999). It appears however to exist in a state and spores in its continental refuge. (Schwenninger of arrested development, unable to produce the 2001). Although the majority of sites generally mature form under present conditions. In Luxem- refl ect this population increase, the remarkable recovery is due largely to the contribution of the bourg the independent gametophyte of Tricho- two sites from which the public has been excluded manes speciosum was fi rst discovered in 1993 (Jermy since 1993. On a global level however, the number pers. comm., Rasbach, Rasbach & Jérôme 1993). of sites is continuing to dwindle. Those sites And again this was the fi rst observation of this - where the fern was considered to be in danger of even more Atlantic - species inside the continent! becoming extinct in 1988 have now disappeared and the total number of individual sites which A� er the fi rst discoveries in the "Petite Suisse" in are physically separated from each other appears Luxembourg, the gametophytes of T. speciosum to have gradually decreased throughout the 20th were found in many places on the continent century. (France, Germany, Belgium, Czech Republic and more recently in Poland (Krukowski & Świerkosz 2004)). In Luxembourg, systematic investigations Prospects and conservation revealed a great number of populations, not only in the Luxembourg Sandstone region, but also on The collection of botanical specimens, undesirable Devonian Schist in the Ardennes region (Krippel silvicultural interventions in the past, activities related to tourism as well as rock climbing, 2001). represent the major threats for the Hymenophyllum sites. Not surprising that the drastic measures to remove the massive human presence at some sites - by se� ing up gates in 1993 - have well contributed to the expansion of some populations. It is however possible that overall climatic condi- tions may have been particularly benefi cial to the growth rates of the fi lmy-fern colonies in recent years, perhaps as a consequence of global warming or that we may be dealing with long-term fl uctua- tions in population cycles. Besides the mentioned gates, some other minor measures and a new set of local bylaws governing the legal conditions under which rock climbing is permi� ed were carried out. But a� empts to enhance the legal protection of fi lmy-fern sites and boost conservation initiatives in the area by Fig. 3: Gametophytes of Trichomanes speciosum (Killar- offi cially designating the entire forest as a national ney fern) on Luxembourg sandstone. Photo: Y. Krippel. nature reserve failed so far. Ferrantia • 44 / 2005 211 Y. Krippel The Hymenophyllaceae (Pteridophyta) in Luxembourg. Past, present and future Fig. 4: Distribution map of Trichomanes speciosum. Grid: Gauss-Luxembourg, square kilometres. 212 Ferrantia • 44 / 2005 Y. Krippel The Hymenophyllaceae (Pteridophyta) in Luxembourg. Past, present and future Distribution and status References Trichomanes speciosum is growing in Luxembourg Jalas J. & Suominen J. (eds.) 1972. - Atlas Florae as an 'independent gametophyte' with vegetative Europae. Distribution of vascular plants in reproduction and dispersion by the way of Europe. Vol.1: Pteridophyta (Psilotaceae to gemmae (Fig. 3). Diff erent studies and systematic Azollaceae). - The Commitee for Mapping the investigations over the last 5 years showed that Flora of Europe and Societas Biologica Fennica the gametophytes of Trichomanes speciosum are Venamo, Helsinki, 121 p. relatively well distributed throughout the 'Petite Suisse' sandstone area with nevertheless 2 major Koltz J.-P. J. 1873. - Hymenophyllum tunbridgense distribution spots. The fi rst one is situated on Sm. - Bull. Soc. roy. Bot. Belg. XII : 449-453. both sides of the 'Ernz noire' between Echternach, Krippel Y. 2001. - Aire de répartition et statut de Berdorf, Beaufort, Waldbillig, Christnach and Trichomanes speciosum Willd. (Hymenophyl- Consdorf, the second one between the 'Ernz laceae) au Grand-Duché de Luxembourg. - blanche' and the Valley of the Alze� e. A third Bull. Soc. Nat. luxemb. 102: 3-13. major distribution area is situated in the Ardennes region, especially in the valley of the Upper-Sûre. Krukowski M. & Świerkosz K. 2004. - Discovery At present date, more than 120 sites are known in of the gametophytes of Trichomanes speciosum 80 diff erent square kilometres (Fig. 4). Even if the (Hymenophyllaceae: Pteridophyta) in Poland species is quite widespread in Luxembourg, the and its biogeographical importance. Fern Gaz. populations occurring in the 'Petite Suisse' are the 17(2): 79-84. most