Acta Botanica 2-2014.indd ACTA BOT. CROAT. 73 (2), 2014 465 Acta Bot. Croat. 73 (2), 465–470, 2014 CODEN: ABCRA 25 ISSN 0365-0588 eISSN 1847-8476 Short communication Muhlenbergia schreberi J. F. Gmel (Poaceae), a new naturalized species in Croatia NEJC JOGAN Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, SI-1000 Ljubljana, Slovenia Abstract – Muhlenbergia schreberi, nimblewill, is a widespread North American peren- nial grass species, slowly spreading in European countries, where it has been recorded in Spain, Switzerland, Italy, and Slovenia. In addition, a well naturalized population was dis- covered in Opatija (Northwestern Croatia, Croatian Littoral) in 2011 as described herein. It has been recognized as a persistent weed in some North American states, and in the last few decades its secondary European distribution range has been slowly increasing. Thus most probably it will also spread in Croatia and become classifi ed as invasive. Keywords: Croatia, Muhlenbergia schreberi, neophyte, nimblewill, potentially invasive species Introduction In the last decades, neophytes have been at the forefront of not only fl oristic research but also of nature conservation, which is becoming more and more aware of their potential im- portance as threats to indigenous biodiversity. So countries mostly have drawn up their lists of aliens or invaders (BORŠIĆ et al. 2008, CELESTI-GRAPOW et al. 2010, JOGAN et al. 2012). Unfortunately, further from the mere act of listing, »the path becomes rough« and so alien species are spreading steadily and more and more new taxa are entering our nature. Not all neophytes are easily recognizable in the fi eld and sometimes their secondary spread remain unnoticed for decades. This is certainly the case with some umbellifers, such as Ammi vis- naga (RUŠČIĆ and NIKOLIĆ 2011) and even more with some of the grasses. Such is the case of Sporobolus neglectus, recorded for the fi rst time in Croatia soon after World War II (MARKOVIĆ 1973), but without any further records until recently, when it has been observed to be already widespread along several main roads in lowland Croatia. Most probably the case of Muhlenbergia schreberi, recently recorded for the fi rst time in Croatia in Opatija, will be similar. * Corresponding author, e-mail: nejc.jogan@bf.uni-lj.si Copyright® 2014 by Acta Botanica Croatica, the Faculty of Science, University of Zagreb. All rights reserved. JOGAN N. 466 ACTA BOT. CROAT. 73 (2), 2014 Muhlenbergia schreberi J. F. Gmel [M. diffusa Willd.] The genus Muhlenbergia Schreb. belongs to the subfamily Chloridoideae with majority of taxa in dry and warmer parts of the world. Of the approximately 160 species, the major- ity are confi ned to America and only about a dozen are also native in the warmer parts of Asia (CLAYTON and RENVOIZE 1986, MABBERLEY 1990, WATSON and DALLWITZ 1992). The genus was named after the Lutheran pastor Heinrich Ludwig Mühlenberg (1756–1817), a famous researcher into North American fl ora, especially grasses (ASCHERSON and GRAEBNER 1898–1902). In Europe, the genus Muhlenbergia is represented by only some ephemerophytes (ASCHERSON and GRAEBNER 1898–1902, RYVES et al. 1996, CONERT 1998) and by M. schre- beri, which is locally naturalized. In addition, some authors include Sporobolus vaginifl orus (A. Gray) A. W. Wood, a naturalized North American annual, in the genus Muhlenbergia as M. vaginifl ora (A. Gray) Jogan (JOGAN 1999, POLDINI et al. 2002). Muhlenbergia schreberi, nimblewill, is a perennial grass 0.1–0.3 m tall with a much- branched geniculate culm rooting at the lower nodes, somehow cespitose. Leaf sheaths are shorter than internodes, with ligule < 0.5 mm long, and leaf blades narrowly lanceolate, fl at, 2–3 mm wide and 3–7 cm long, more or less perpendicular to the culm. Infl orescence is a distinctly contracted interrupted panicle, up to 20 cm long, with short branches, nodding, spikelets are numerous, on short pedicels, one-fl owered, < 2.5 mm long (awn not included). Glumes are very reduced, < 0.5 mm long, lemma appressedly hairy, 2–2.5 mm long, taper- ing into a straight weak 2–5 mm long awn, distinctly 3-nerved, and a palea slightly shorter than lemma, visible. Stamens are only slightly protruding at the top of the spikelet during anthesis, with yellow anthers 0.2–0.4 mm long. After anthesis, ripe spikelets disarticulate above the persistent glumes, caryopsis 1.3 × 0.3 mm. 2n = 40. Flowering time is late, Sep- tember and October. The primary distribution of M. schreberi is in the eastern part of North America, from central Mexico to south-east Canada, and South America southwards to North Argentina. The centre of its distribution range seems to be in the eastern half of the USA. In South America it is reported for the warm temperate belt, i.e. for North Argentina (NICORA and RUGOLO de AGRASAR 1987), and is much rarer in Colombia, South Uruguay and South Bra- zil. In its secondary distribution range, in Switzerland nimblewill is restricted to the Ticino/ Tessin canton in the south fi rst recorded by Becherer in 1963 (CONERT 1998) where it is still locally naturalized (AESCHIMANN and BURDET 1994, LAUBER and WAGNER 2001). In neighbor- ing north Italy it is reported for Piedmont, Lombardy, Trentino-Alto Adige (AESCHIMANN et al. 2005), and Bolzano/Südtirol (FISCHER et al. 2008). In Slovenia it has been naturalized at least since the 1980s in the sub-Mediterranean part on the junction between Kras plateau and Vipava valley (JOGAN 1990) and has been recently recorded naturalized in Litija (central Slovenia, unpublished). There was a neglected occurrence in north-eastern Spain (Catalun- ya, Bordils 10 km north-east of Girona) where the species was collected in 1932 in alluvial forest plantations of Platanus and Populus but it was discovered again in 2007 (PYKE 2008). On the one hand this shows the persistence of the population and on the other hand the gen- eral fl oristic neglect of grasses. Because of its occurrence in Spain and Italy, it could be ex- pected to be found in France. It has also been recorded as a casual in United Kingdom (RYVES et al. 1996). MUHLENBERGIA SCHREBERI IN CROATIA ACTA BOT. CROAT. 73 (2), 2014 467 In the former USSR (CVELEV 1976) M. schreberi is reported from the Caucasian region (North Ossetia, West Transcaucasia, today Georgia) and Armenia, but its occurrence there is defi nitely not native as it is wrongly reported to be in Euro+Med PlantBase (http://ww2. bgbm.org/euroPlusMed). In Japan it is listed among invasive alien species as established (http://www.nies.go.jp/biodiversity/invasive/). Its occurrence seems secondary also in the western USA, where nimblewill is treated as a noxious weed in California (PETERSON 2003). In South America the ecological conditions of M. schreneri are reported as hygrophilous subtropical forests and gallery forests (NICORA and RUGOLO DE AGRASAR 1987). In North America its ecology seems very diverse (PETERSON 2003, 2007). Judging from the 89 herbarium labels from Smithsonian (http://collections. si.edu/) of which about half mention the habitat type, it has mostly been collected in ruderal places (17/43), various types of wetlands (12/43), grasslands (8/43) and woods or shaded places (6/43), which is certainly only a rough estimation of the author, but clearly shows the habitat type preferences. HITCHCOCK and CHASE 1971 simplify its ecology to »damp shady places«. In the Caucasus region the grass was reported as a weed in plantations of subtropical plants (CVELEV 1976). In Switzerland M. schreberi is reported as a new-comer to an aban- doned landfi ll site together with several other neophytes (BELLOSI et al. 2011) and in general it is scattered on road banks, lawns and among shrubs (LAUBER and WAGNER 2001) and sev- eral other ruderal places and forests (CONERT 1998). It prefers weakly acid substrates with enough humus, slightly sandy. In Northeast Spain, where M. schreberi populations have persisted for more than 70 years, it is reported to grow in river banks, wet and ruderal plac- es (PYKE 2008). In Slovenia, the habitat types of M. schreberi are ruderal, forest fringes on shady slopes and meadows (JOGAN 1990). In the whole wider area of the Alps M. schreberi is recognized as a species of Geo-Alliarion type of vegetation (AESCHIMANN et al. 2005). Methods The newly discovered locality of M. schreberi is the outcome of the author’s systematic fl oristic fi eld work focused on grasses. Mapping is conducted in the frame of the informal international project »Flora of Istria« (STARMÜHLER 1998) comprising the wider territory of Istria south of the line Trieste-Rijeka including the northern part of the Kvarner archipelago, coordinated by W. Starmühler (Graz, Austria). The fl oristic activities of several dozen col- laborators have been carried out for roughly 15 years and preliminary results such as check- lists and herbarium revisions have been published in a series of articles starting with STAR- MÜHLER 1998. Herbarium vouchers are deposited in public herbaria and duplicates are offered to collaborating institutions. The fi rst collection of M. schreberi is deposited in her- barium LJU (University of Ljubljana, Biotechnical faculty). Results and discussion The fi rst known population of M. schreberi in Croatia (Fig. 1) was recorded in the Kvar- ner Littoral, in Opatija, on lawns, forest fringes and ruderal places near the Hotel Ambasa- dor, 45°20'26"N, 14°18'41"E, 0651/4 (leg. N. Jogan 11. 12. 2011, herbarium LJU). The population is hard to analyze because it is scattered over a frequently mown lawn on the south oriented slope in front of the hotel. The lawn is about 100 × 30 m in size and a few JOGAN N. 468 ACTA BOT. CROAT. 73 (2), 2014 dozen stands of M. schreberi of different sizes up to a few square meters are scattered all over the lawn. Due to very frequent mowing, only some culms can be found fl owering, but with its stolons this perennial plant is slowly spreading and it can be recognized quite easily during the winter by its dry whitish leaf blades or during the vegetation period by the quite dense leaves distinctly in two rows on vegetative shoots. Propagation and further spread at the locality might be enhanced by frequent mowing that results in small parts of the stolons being dispersed and rooting at the nodes; propagation by seed is not to be excluded, how- ever. In the autumn, the fl owering period of M. schreberi, only a couple of accompanying plant species are fl owering, e.g. Cynodon dactylon, Bothriochloa ischaemum, on more ru- deral margins Digitaria sanguinalis, Setaria viridis and also an interesting American ephem- erophyte Cyclospermum leptophyllum (Pers.) Sprague ex Britton and P. Wilson which had not been recorded in Croatia previously. In its native range M. schreberi is treated as a troublesome weed (BROWN 1979) espe- cially in lawns, as it slowly spreads by stolons and patches on lawns gradually increase, but in autumn does not remain green, like other lawn grasses. It will at fi rst turn brown, and then, until the late spring the withered pale brown leaves are easily noticed as »dry« patches in the lawn. Green leaves develop later in spring. Because of the vegetative spread of the many- branched stolons, M. schreberi stands are almost without other plant species. Also in sev- eral other weed lists M. schreberi has a status ranging from »casual alien« to »noxious weed« (compilation in Global Compendium of Weeds, http://www.hear.org/gcw/species/ muhlenbergia_schreberi/), e.g. in California, Kentucky, Nebraska and Great Plains it is list- ed as invasive weed. Fig. 1. Muhlenbergia schreberi. a) typical summer aspect with densely growing shoots bearing almost perpendicular linear leaf blades; b) autumn aspect, when long narrow nodding panicles are developed; c) detail of panicle from herbarium specimen; d) spikelet, awned lemma and palea visible. Pictures a) and b) were taken at a locality in Litija, Slovenia, as it was not possible to get such well developed plants in the Opatija locality, while pictures c) and d) were taken from a herbarium specimen collected at the Opatija locality. All photos were taken by N. Jogan. MUHLENBERGIA SCHREBERI IN CROATIA ACTA BOT. CROAT. 73 (2), 2014 469 Some authors recognize M. schreberi in Europe as invasive or at least naturalized, but judging from the situation in its homeland, America, where the species is described as »noxi- ous weed« or »environmental weed« (see above), in its secondary distribution range too it can slowly become at least a local weed of the ruderal places, if not an invasive grassland species. In Europe it is listed as neophytic threat in Italy (as »invasive« in Lombardy and Veneto, »naturalized« in Piedmont, »casual« in Alto Adige; CELESTI-GRAPOW et al. 2010), Switzerland (status »unknown« by WITTENBERG ed. 2006 and later corrected to »natural- ized« on web version of the same document, see http://www.sib.admin.ch/uploads/media/ UW-0629-E.pdf) and Slovenia (»potentially invasive«, JOGAN et al. 2012). We can conclude that for several decades nimblewill has obviously been a well natural- ized species in several European countries with some Mediterranean climatic impact. It is slowly spreading by seeds and vegetatively, and as a late-fl owering grass its occurrence is often overlooked. Most probably also in the newly recorded locality in Opatija the species has been present for several years already and thorough fi eld work in autumn will certainly reveal more populations scattered in the Kvarner Littoral. At the moment, its occurrence seems confi ned to ruderal places, but diversity of microhabitats and conditions similar to those in natural habitat types (e.g. forest fringes, wet grasslands, even rocks) suggests its possible spreading in the vicinity. In Croatia M. schreberi can be listed as a naturalized neophyte, most probably not (yet) as an invasive species, but the wider geographical area adjacent to the discovered locality needs to be explored. References AESCHIMANN, D. LAUBER, K, MOSER, D. M., THEURILLAT, J.-P., 2005: Flora Alpina 2. Haupt Verlag, Bern, Stuttgart, Wien. AESCHIMANN, D., BURDET, H. M., 1994: Flore de la Suisse et des territories limitrophes. 2. Aufl . Le Nouveau Binz, Neuchatel. ASCHERSON, P., GRAEBNER, P. 1898–1902: Synopsis der mitteleuropäischen Flora 2/1. Wil- helm Engelmann, Leipzig. BELLOSI, B, SELLDORF, P., SCHOENENBERGER, N., 2011: Exploring the fl ora on inert landfi ll sites in southern Ticino (Switzerland). Bauhinia 23, 1–16. BORŠIĆ, I., MILOVIĆ, M., DUJMOVIĆ, I., BOGDANOVIĆ, S., CIGIĆ, P., REŠETNIK, I., NIKOLIĆ, T., MITIĆ, B. 2008: Preliminary check-list of invasive alien plant species (IAS) in Croatia. Natura Croatica 17, 55–71. BROWN, L., 1979: Grasses, an identifi cation guide. Houghton Miffl in Co., Boston. CELESTI-GRAPOW, L., PRETTO, F., CARLI, E., BLASI, C.:2010: Flora vascolare alloctona e inva- siva delle regioni d’Italia. Casa Editrice Universita La Sapienza, Roma. CLAYTON, W. D., RENVOIZE, S. A., 1986: Genera Graminum. HMSO, London. CONERT, H. J., 1998: Gramineae. In: HEGI, G. (ed.), Illustrierte fl ora von Mitteleuropa. Paul Parey, Hamburg. CVELEV, N. N., 1976: Zlaki SSSR. Nauka, Leningrad. FISCHER, M. A., ADLER, W., OSWALD K., 2008: Exkursionsfl ora. Österreich, Liechtenstein, Südtirol. Biologiezentrum der Oberösterreichischen Landesmuseen, Linz. JOGAN N. 470 ACTA BOT. CROAT. 73 (2), 2014 HITCHCOCK, A. S., CHASE A., 1971: Manual of the grasses of the United States. Dover, New York. JOGAN, N., BAČIČ, T., STRGULC KRAJŠEK, S., 2012: Neobiota from Slovenia, Final report of the project. Retrived October, 2012 from http://www.bioportal.si/neobiota.php. JOGAN, N., 1990: Contribution to the knowledge of grasses (Poaceae) in Slovenia (in Slove- nian). Biološki vestnik 38, 27–38. JOGAN, N. 1999: Grass – Poaceae. In: MARTINČIČ, A., WRABER, T., RAVNIK, V., JOGAN, N., PODOBNIK, A., TURK, B., VREŠ, B. (eds.), Little fl ora of Slovenia (in Slovenian), 711–813. Tehniška založba Slovenije, Ljubljana. LAUBER, K., WAGNER, G., 2001: Flora Helvetica, 3. Aufl . Haupt Verlag, Bern, Stuttgart, Wien. MABBERLEY, D. J., 1990: The Plant-book. Cambridge University Press, Cambridge. MARKOVIĆ, L., 1973: Sporobolus neglectus Nash, new adventitious species in Yugoslavia (in Croatian). Acta Botanica Croatica 32, 237–242. NICORA, E. G., RUGOLO DE AGRASAR, Z., 1987: Los generos de gramineas de America Aus- tral. Editorial Hemisferio Sur, Buenos Aires. PETERSON, P. M., 2003: Muhlenbergia Schreb. In: BARKWORTH, M. E., CAPELS, K. M., LONG S., PIEP, M. B. (eds.), Flora of North America 25. Magnoliophyta: Commelinidae (in part): Poaceae, part 2., 145–200. Oxford University Press, New York. PETERSON, P. M., 2007: Muhlenbergia Schreb. In: BARKWORTH, M. E., ANDERTON L. K., CA- PELS K. M., LONG S. (eds.), Manual of grasses for North America, 219–230. USU Press, Logan. POLDINI, L. VIDALI, M., ORIOLO, G., 2002: Nuovo Atlante corologico delle piante vascolari nel Friuli Venezia Giulia. Regione autonoma Friuli Venezia Giulia, Azienda parchi e foreste regionali & Universita degli studi di Trieste, Dipartimento di biologia. Udine. PYKE, S., 2008: Contribución al conocimiento de la fl ora alóctona catalana, Collectanea Botanica 27, 95–104. RUŠČIĆ, M., NIKOLIĆ, T., 2011: Ammi visnaga (L.) Lam. (Apiaceae), a new taxon in Croatian fl ora. Acta Botanica Croatica 70, 301–306. RYVES, T. B., CLEMENT, E. J., FOSTER, M. C., 1996: Alien grasses of the British Isles. BSBI, London. STARMÜHLER, W., 1998: Vorarbeiten zu einer »Flora von Istrien« I. Carinthia II 188/108, 535–576. WATSON, L., DALLWITZ, M. J., 1994: Grass genera of the World: descriptions, illustrations, identifi cation, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classifi cation, pathogens, world and local distri- bution, and references. Retrived from http://delta-intkey.com/grass. WITTENBERG, R., 2006: An inventory of alien species and their threat to biodiversity and economy in Switzerland. CABI Bioscience Switzerland Centre report to the Swiss Agency for Environment, Forests and Landscape. The environment in practice no. 0629. Federal Offi ce for the Environment, Bern.