Acta Botanica 1-2015 - za web.indd ACTA BOT. CROAT. 74 (1), 2015 173 Acta Bot. Croat. 74 (1), 173-179, 2015 CODEN: ABCRA 25 ISSN 0365-0588 eISSN 1847-8476 Short communication Re-evaluation of the Panicum capillare complex (Poaceae) in Croatia GERGELY KIRÁLY1*, ANTUN ALEGRO2 1 University of West Hungary, Institute of Silviculture and Forest Protection, Ady E. u. 5, H-9400 Sopron, Hungary 2 University of Zagreb, Faculty of Science, Department of Botany and Botanical Garden, Marulićev trg 9a, HR-10000 Zagreb, Croatia Abstract – The Panicum capillare complex includes several taxa, among them P. capil- lare L., which is usually considered to be an established alien throughout Europe, whereas other species are recorded only as casuals. A new representative of the complex, P. ripari- um H. Scholz was described from Germany in 2002, and shortly after its description was recorded in several countries on the continent. In the course of herbarium revisions and recent fi eld studies the authors documented several localities of the species in Croatia as well. The paper presents a new key for the determination of Croatian species of the com- plex and anticipates the invasion of P. riparium in the sub-Mediterranean regions of the Balkan Peninsula. Keywords: Balkan Peninsula, determination key, invasive alien, neophyte, Panicum cap- illare agg. Introduction The genus Panicum L. is one of the largest genera of grasses with about 300 species worldwide. The majority of species are of tropical or subtropical origin (ZULOAGA and SOD- ERSTROM 1985, FRECKMANN and LELONG 2003, 2007, SHOULIANG and RENVOIZE 2006). Re- cently, the number of species in the genus has been considerably reduced through segrega- tion of many species into smaller genera (ALISCIONI et al. 2003). Several species play an important role as feed and forage in different ecosystems of the world, and, under anthropo- genic infl uences many species have signifi cantly expanded their distribution as agricultural weeds or ruderals (RYVES et al. 1996, VAN DE WOUW et al. 2008, MORAVCOVÁ et al. 2010). The majority of Panicum species recognized in central and southern Europe belong to sect. * Corresponding author, e-mail: kbgergely@gmail.com Copyright® 2015 by Acta Botanica Croatica, the Faculty of Science, University of Zagreb. All rights reserved. KIRÁLY G., ALEGRO A. 174 ACTA BOT. CROAT. 74 (1), 2015 Panicum L. (leaf sheaths rounded and hairy, lower glumes acute to attenuate) and sect. Di- chotomifl ora (Hitch.) Honda (leaf sheaths compressed, glabrous, lower glumes truncate to subacute) (CONERT 1979, CLAYTON 1980, FRECKMANN and LELONG 2003). The Panicum capillare complex (sect. Panicum, »witchgrasses« native to North Ameri- ca) includes taxa, which were taxonomically evaluated in different ways. Employing a typi- cal central European »disaggregate approach«, SCHOLZ (2002) distinguished several taxa at species rank, whereas Anglo-Saxon taxonomists (»aggregate approach«) tend to reduce the number of species through assessment of taxa at the rank of subspecies or variety (CLEM- ENTS el al. 2004, FRECKMANN and LELONG 2003, 2007). These contractions do not signify that these taxa are conspecifi c, but some authors consider the differences to be too small and the degree of variety too great to accept them as »good species«. It should be noted that the American determination keys to the discussed complex usually focus only on the length of mature spikelets and ignore other features (e.g. form of lemmas, form of panicle). Among the representatives of the complex, Panicum capillare L. is described as a natu- ralized alien throughout Europe (CLAYTON et al. 1980), whereas other species were recorded in certain countries (e.g. P. gattingeri Nash and P. hillmannii Chase in Austria and Slovenia; JOGAN 2007, FISCHER 2008) as rare casuals only. From Croatia only P. capillare has been reported (DOMAC 1994, EURO+MED 2006, NIKOLIĆ 2014). Panicum riparium H. Scholz (2002: 275) was recently described as a new species from the Elbe Valley in Germany. Whereas SCHOLZ (2002) emphasized that P. riparium and P. barbipulvinatum Nash are not conspecifi c, the exhaustive study of AMARELL (2013a, b) showed that the names are probably synonymous. Although some authors (HOHLA 2013, VERLOOVE 2014) have already adopted the name P. barbipulvinatum for some newer re- cords, widespread use of this name in the case of central European plants should be dis- couraged until type material of all related North American taxa has been investigated. Her- barium revisions of the P. capillare complex have shown that P. riparium is not a new invader but an overlooked, long-established taxon in central Europe, and, in some parts of the synanthropic European range, is more abundant than P. capillare s. str. (WILHALM 2011, NAGY et al. 2012, AMARELL 2013b). According to these fi ndings, its occurrence in Croatia was to be expected, which has necessitated a re-evaluation of the complex in the area. Material and methods Specimens in the following herbaria (acronyms given according to THIERS 2014) were searched for records of the Panicum capillare complex: BP, BPU, DE, GJO, JPU, LJU, PECS, W, ZA, ZAHO, and the private herbarium of the fi rst author. Not only were the his- torical collections revised, but a new voucher specimen of P. riparium was placed in ZA. Characterization of P. capillare s. str. and P. riparium was based on the revision of 20 spec- imens for each as a reference derived from the herbaria listed above, the keys of SCHOLZ (2002), FISCHER et al. (2008), KIRÁLY et al. (2009) and AMARELL (2013b) were also applied. Field studies in northern Croatia were conducted in 2012 and 2013. For the new locality of Panicum riparium, geo-coordinates were determined using a Trimble Nomad GPS hand- held device in WGS 84 projection. Quadrant numbers (»MTB«) of the central-European Flora Mapping System are presented after NIKOLIĆ et al. (1998). THE PANICUM CAPILLARE COMPLEX IN CROATIA ACTA BOT. CROAT. 74 (1), 2015 175 Results and discussion Panicum riparium is readily distinguished from P. capillare s. str. using macroscopic characters by the structure of the panicle and the form of spikelets. For further confi rmation of the determination some measurements of spikelets and fruits are useful (see the key be- low and Fig. 1). Determination key for Croatian species of Panicum capillare complex: 1a. Pedicel of subterminal spikelet longer than 5 mm, patent (angle between subterminal and terminal pedicels 20–60°). Mature spikelet 2.2–2.7× as long as broad, acute, short pointed; lemma (7–)9 veined. Caryopsis 1.5–1.7× as long as broad . . . . . P. capillare s. str. 1b. Pedicel of subterminal spikelet shorter than 3 mm, appressed to the branch (angle be- tween subterminal and terminal pedicels < 10°). Mature spikelet 2.7–3.4× as long as broad, acuminate with a long tapering apex; lemma 5(–7) veined. Caryopsis 1.8–2.2× as long as broad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P. riparium In the course of systematic revision of herbarium material of the P. capillare complex, several overlooked specimens of P. riparium, a new species for the Croatian fl ora, were found in BP and ZA. The earliest collection is dated to the second half of the 1800s, how- ever, its exact location and date are not given. The fi rst precisely dated specimen was col- lected in the early 1900s in the present-day Rijeka. From the 1950s P. riparium was re- peatedly collected in the vicinity of Zagreb, and further fi ndings are known from the Fig. 1. Panicum capillare L.: (a) panicle; (b) detail of panicle; (c) mature spikelets; Panicum riparium H. Scholz: (d) panicle; (e) detail of panicle; (f) mature spikelets. Del. J. Táborská. KIRÁLY G., ALEGRO A. 176 ACTA BOT. CROAT. 74 (1), 2015 sub-continental (Slavonski Brod), sub-Mediterranean (Knin, Rijeka) and Mediterranean (Vodice) parts of Croatia. In the course of the fl oristic investigation of the Ivanščica Moun- tain, a recent occurrence of P. riparium was documented in 2013 (see Appendix 1 and Fig. 2). During the revision we recorded only fi ve Croatian collections of P. capillare s. str. (see Appendix 2), thus we consider that it is distinctly rare in the country. Shortly after its description in Germany (SCHOLZ 2002), P. riparium was reported from several countries in central Europe: Austria (HOHLA 2006), Hungary (KIRÁLY et al. 2009), Germany (AMARELL 2010), Switzerland (CIARDO et al. 2011), Italy (WILHALM 2011), France and Great Britain (AMARELL 2013b), and Belgium (VERLOOVE 2014), due to actual fl oristic research in the fi eld and herbarium revisions. Accompanying P. capillare s. str., P. riparium was often recorded as well, thus showing that both species coexist on the continent. The relative abundance of these taxa is not yet known in the individual countries. Nevertheless, P. riparium seems to have a slight sub-Atlantic character with the (hitherto known) Euro- pean distribution centre north of the Alps. Representatives of the P. capillare complex grow usually in ruderal habitats (roadsides, building sites) in Europe; their occurrences in agricultural habitats are much less frequent, whereas they are serious weeds in North America, infesting predominantly corn, soybean and winter wheat cultures (DARBYSHIRE and CAYOUETTE 1995, CLEMENTS et al. 2004). P. ri- parium was reported from Hungary exceptionally as an abundant agricultural weed on acidic sandy soils (NAGY et al. 2012). Fig. 2. Distribution of Panicum riparium H. Scholz in Croatia. THE PANICUM CAPILLARE COMPLEX IN CROATIA ACTA BOT. CROAT. 74 (1), 2015 177 In Croatia P. capillare has been described as an invasive alien (BORŠIĆ et al. 2008), and as a particularly noxious agricultural weed (HULINA 2010). However, several former reports without voucher may refer to P. riparium, newly published records of which are a clear in- dication of a presumable invasion in the sub-Mediterranean and Mediterranean regions. The Croatian records from Knin and Vodice represent the southernmost reported localities of the latter species in Europe. Exhaustive fi eld studies and herbarium revisions are needed to assess the actual distribution and role of P. riparium in the northern part of the Balkan Peninsula because of the prospect of rapid invasion in secondary habitats. Acknowledgements Thanks are due to Uwe Amarell (Offenburg, Germany) for discussions on the origin and distribution of Panicum riparium in Europe. Richard Lansdown (Stroud, Great Britain) kindly improved our English. The study of Gergely Király was supported by project Agrár- klíma.2 VKSZ-12-1-2013-0034. 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Recorded localities of Panicum riparium H. Scholz in Croatia. »in agris«; C. J. Schlosser (as »P. capillare«), n. d., ZA16220; Fiume (today Rijeka), »in ruderatis viae ferrae« (probably MTB 0652.4), G. Lengyel (as »P. capillare«), VIII. 1908, BP356966; Kamena Gorica, N of the settlement, N46.162662°; E16.256507° (MTB 9863.2), G. Király & D. Schmidt, 07. IX. 2013, ZA; Knin, railway station (MTB 1963.3), M. Milović (as »P. capillare«), 12. XI. 2000, ZA16208; Slavonski Brod, Poloj, bank of Drava river (MTB 0874.3), L. Marković (as »P. capillare«), 08. IX. 1969, ZA16214; Stubičke Toplice (MTB 0061.2), N. Fiket (as »P. capillare«), 29. VIII. 1955, ZA16218; Vodice (MTB 2260.2), M. Milović (as »P. dichotomifl orum«), 10. VIII. 1999, ZA16210; Zagreb, »garden« (MTB?), I. Horvat (as »P. capillare«), 18. IX. 1948, ZAHO; Zagreb, Bo- rovje (MTB 0161.4), L. Marković, L. Gospodarić (as »P. capillare«), 09. IX. 1954, ZA16211; Zagreb, Lanište (MTB 0261.2), A. Kumbarić (as »P. capillare«), 25. VIII. 1992, ZA16216; Zagreb, Savski most (MTB 0261.2), L. Marković (as »P. capillare«), 26. VIII. 1959, ZA16217; Zagreb, W of »Savski most« (MTB 0261.2), L. Marković (as »P. capil- lare«), 03. X. 1969, ZA16215; Zagreb, Sesvete (MTB 0162.4), B. Hundozi (as »P. capil- lare«), 04. IX. 1964, ZA16214. Appendix 2. Herbarium specimens of Panicum capillare L. found in Croatian herbaria. Gunja, near the railway bride on Sava (MTB 1179.1), L. Marković, 10. IX. 1969, ZA16213; Medvednica, Adolfovac, forest cutting (MTB 0161.2), L. Marković, 08. IX. 1974, ZA11846; Negoslavci, on row crops (probably MTB 0779.2), M. Jakovlević, 15. VIII. 1956, ZA16219; Ozalj, on row crops SW of railway station (MTB 0358.4), L. Ilijanić (as »P. dichotomifl orum« but fragments of the collection belong to P. capillare), 12. XI. 1986, ZA; Trakošćan, on row crops (MTB 9761.2), S. Kečkeš (as »P. miliaceum«), 13. VIII. 1956, ZA16207.