ISSN 1989‐8649 Manag. Biolog. Invasions, 2010, 1

Abstract Invaders in disguise. Conservation risks derived from misidentifications of invasive Misidentifications are an important but neglected problem in studies on Filip VERLOOVE invasions. This review shows how taxonomic education of staff and stakeholders is of great importance for correctly assessing threats provoked by Introduction, Hypotheses and not only unverifiable; they are often alien plant species in field and literature Problems for Management also unreliable. Pyšek (2003) based studies. demonstrated that Czech data Biological invasions have become a extracted from the monumental Four randomly chosen recent major concern in the past decades Flora Europaea where surprisingly examples (Digitaria violascens, unreliable: numerous taxa were Eleocharis pellucida, dichotomus since they are believed to be and Vicia dalmatica) from Europe responsible for declining omitted and others were demonstrate that, as a result of an biodiversity worldwide. Especially in erroneously included. A catalogue of initial erroneous identification and/or North America, Australia and Europe neophytes in Belgium (Verloove confusion with similar harmless species, numerous scientists are now 2006) was therefore based on a potentially noxious environmental involved in the study of non‐native thorough revision of the main public weeds have been able to become fully organisms. Their scope is Belgian herbaria. About 20% of the naturalised. They act as “invaders in exceedingly diverse and includes, taxa was not previously recorded disguise” and therefore constitute a real among others, the elaboration of (unidentified or erroneously problem for conservation management. checklists and catalogues, pest risk identified before, confused with management, traits assessment, etc. similar or related taxa, etc.). On the other hand not less than 30 taxa Keywords In many parts of Europe from the Belgian flora needed to be , alien species, Digitaria studies on non‐native vascular omitted because they were violascens, Eleocharis pellucida, Juncus plants have yielded an extraordinary incorrectly included (Verloove & dichotomus, Vicia dalmatica amount of valuable data. Most Lambinon 2008). Bio‐sketch countries by now have published catalogues or checklists that provide It is generally accepted that The author has been studying non‐ information on such items like the an early detection of new native plants (ephemerals as well as degree of naturalisation, time and xenophytes is essential. However, invasives) for some 20 years by now. His mode of introduction, origin, habitat this firstly requires an accurate work chiefly emphasizes on recognition preferences, chorology, biology (for determination. It is obvious that a (identification) and taxonomy. F. instance life form), etc. Logically, correct identification is an essential Verloove has produced lots of these data are usually taken from and primary tool in studies on non‐ publications on naturalized vascular literature since databases with native vascular plants. Not before a plants in Europe. Since several years, he literature references are very correct name has been established is working on online "Manual of alien manageable and easy to access. for a given alien taxon, its pest risk plants of Belgium". However, several studies have can be assessed. Alas, the above proved that data from literature are proves that misidentifications still

1 DOI: http://dx.doi.org/10.3391/mbi.2010.1.1.02 Verloove, F. 2010. Manag. Biolog. Invasions, 1: 1‐5 F. Verloove. Invaders in disguise: conservation risks obviously of non‐European origin native species in these areas and Resumen (for instance Eichhornia crassipes recent records were considered to (C.F.P. Mart.) Solms‐Laub., Ludwigia be valuable. Eventually they most Los errores en la identificación de grandiflora (Michaux) Greuter & likely are erroneous due to especies son un problema común en los Burdet, Opuntia div. spec., etc.). confusion with Digitaria violascens. estudios sobre plantas invasoras. En However, in the past years it has Digitaria violascens now proves to esta revisión se muestra cómo la become clear that an increasing be a typical example of an invader in educación taxonómica de los number of non‐native vascular disguise. Since Verloove (2008) it trabajadores y gestores es de enorme plants managed to become was furthermore reported by Pyke importancia para evaluar naturalised or even invasive in parts (2008) and Verloove & Sánchez correctamente las amenazas of Europe without ever being Gullón (2008) but it was estimated provocadas por especies vegetales alóctonas en estudios de campo o noticed! Such species can be either to be merely locally naturalised and basados en literatura. very inconspicuous (for instance mainly confined to irrigated lawns. several Lemnaceae) or (and more However, fieldwork in September Escogidos al azar cuatro ejemplos frequently) very reminiscent of 2009 in northwestern Italy showed recientes de Europa (Digitaria related native or harmless non‐ that Digitaria violascens has become violascens, Eleocharis pellucida, Juncus native species. They are here exceedingly common in parts of dichotomus and Vicia dalmatica) se designated as “invaders in disguise” Piemonte (and doubtlessly demuestra que, como resultado de and surely act as a new challenge to elsewhere). It now commonly occurs determinaciones iniciales erróneas o plant taxonomists and ecologists. by road verges and wasteland. por confusión con especies semejantes However, it also penetrates in que no suponen peligro, las verdaderas Some recent examples of natural habitats: it is a typical especies invasoras que pasaron misidentified plant taxa element of riparian associations in a desapercibidas han sido capaces de fairly large number of river valleys llegar a naturalizarse por completo. De Digitaria violascens Link (Poaceae) (Fig. 1). Even more regrettable is its esta forma actúan como ‘invasoras presence in the many heaths of disfrazadas’ y constituyen un problema This crabgrass is probably of South Piemonte, most of which are real en el manejo de la biodiversidad. American origin but now occurs as a vulnerable and protected areas (for Palabras clave weed of arable land, irrigated lawns instance the Riserva Naturale della etc., in tropical and subtropical Vauda north of Torino and all Parco Taxonomía, especies alóctonas, Digitaria areas of both the New and Old Baragge areas in the surroundings of violascens, Eleocharis pellucida, Juncus dichotomus, Vicia dalmatica World. It is exceedingly reminiscent Novara and Vercelli). In these of the native European Digitaria heaths Digitaria violascens obviously ischaemum (Schreb. & Schweigg.) benefits from the practices Muhl. Verloove (2008) recently commonly used to maintain a semi‐ demonstrated that Digitaria natural, open vegetation (see also violascens is known since at least Lonati & al. 2009 for an identical the 1990’s from southern France case with the American grass and parts of Italy and Spain where it Panicum acuminatum Swartz in has been confused with D. Italian heaths). Since it has been ischaemum. The latter is a rare confused with native Digitaria

Verloove, F. 2010. Manag. Biolog. Invasions, 1: 1‐5 2 ISSN 1989‐8649 Manag. Biolog. Invasions, 2010, 1

ischaemum its occurrence and spread to suitable habitats in the with which is one of spread logically have never been of surrounding heaths. the most widespread xenophytes in any concern. In a heath near Europe (DAISIE 2008). It occurs in Cossato (E of Biella) Digitaria Eleocharis pellucida is exceedingly natural habitats (including heaths, violascens now is the dominant similar to the native Italian E. clearings and tracks in woodland, species, along with Euthamia carniolica. The latter is a very rare etc.) and man‐made habitats graminifolia (L.) Nutt. (syn.: Solidago and vulnerable species and by now (railway yards, cracks in pavements graminifolia L.), another American extinct in many of its classical in urban areas, etc.). xenophyte. localities (Lastrucci & Becattini 2007). It is one of the target species Even in the first case it is Digitaria violascens by now is so for nature conservation seldom regarded as a noxious common in northwestern Italy that management and hence of high environmental weed even though it it must have been introduced quite concern in several nature reserves often occurs in abundance. Juncus some time ago. By the time it was (including the Riserva Naturale della dichotomus, on the contrary, is a finally recognised it has been able to Vauda north of Torino). Both species more specialised species and more spread in a fast way and now has surely have been confused and confined to at least temporarily wet occupied valuable natural habitats increasing or new populations of habitats (see for instance Correll & (including nature reserves and other presumed Eleocharis carniolica Correll 1975): riverbanks, pond protected areas). might as well refer to E. pellucida. margins, depressions in heaths, Both species often grow sometimes also near rice fields. It Eleocharis pellucida Presl sympatrically and practices of behaves in the same way in Italy and (Cyperaceae) conservation management that future invasive behaviour cannot be should favour native Eleocharis ruled out (see also Randall 2002 or This is a noxious Asian weed carniolica are probably also of www.hear.org/gcw/). It seems that of rice fields and other temporarily benefit to the non‐native but Juncus dichotomus is a relatively damp habitats (Figs 2‐3). It was hitherto unrecognised weed E. recent xenophyte in Europe discovered in abundance in 2008 in pellucida. (although herbarium revisions of J. shallow depressions and tracks in a tenuis might bring to light new heath near Benna in Piemonte Juncus dichotomus Elliott records). It seems appropriate to (northwestern Italy). Additional field () closely watch its future expansion. work in September 2009 yielded several supplementary records from This is a New World species of other heaths in the same area the J. tenuis Willd. complex. Some Vicia dalmatica A. Kern. (Fabaceae) (Verloove 2010). It is clearly well years ago it was discovered near established in natural and Novara in northwestern Italy. In This is a member of the Vicia cracca vulnerable habitats and its initial September 2009 more profound L. complex and is most closely introduction probably dates back to fieldwork yielded several new related to V. tenuifolia Roth. Its several decades ago. It was most localities in Piemonte (personal natural distribution range is in likely formerly introduced as a weed observations author). This species is southeastern Europe. in the vast rice‐growing area around obviously well established locally The Montagne Saint‐Pierre in Benna and eventually managed to and must have been confused so far Belgium – a nature reserve with sun‐

3 Verloove, F. 2010. Manag. Biolog. Invasions, 1: 1‐5 F. Verloove. Invaders in disguise: conservation risks

exposed calcareous slopes and lots has been enhanced by conservation case scenario an invasive exotic of Orchidaceae – harbours one of practices. weed can proliferate as a result of the last Belgian populations of conservation management practices presumed native Vicia tenuifolia. Analogously, Vicia dalmatica that were in fact meant to favour Species‐specific conservation managed to become naturalised in vulnerable, native species, simply management proved to be numerous calcareous and because it was initially misidentified. successful and has ensured its thermophilous grasslands in Central‐ It is obvious that field workers survival since at least the 1940’s. Europe. Like in Belgium it was only should be aware for such invaders in However, a critical revision of these relatively recently detected but disguise. Determinations should be populations recently demonstrated must have been present since quite critically assessed, in case of doubt that not the native and vulnerable some time. preferably by experts. A sudden and Vicia tenuifolia was concerned but Conclusions unexpected expansion of rare, the non‐native V. dalmatica. This presumably native species might as means that, as a result of an initial These four recent examples show well hide an incipient invasion of a erroneous identification, a that an early detection and accurate noxious non‐native look‐alike. xenophyte has been able to become identification are essential tools in perfectly established and its survival plant invasion research. In a worst

b)

a)

Fig. 1. Typical habitats of Digitaria violascens. 1a) River Elvo near Salussola; 1b) Parco Baragge in Benna, heath; 1c) Track in remote riparian woodland along river Elvo near Arro, invaded by Digitaria violascens.

c)

Verloove, F. 2010. Manag. Biolog. Invasions, 1: 1‐5 4 ISSN 1989‐8649 Manag. Biolog. Invasions, 2010, 1

Fig. 2. Vauda Nature Reserve near Lombardore, typical habitat of Eleocharis pellucida and E. carniolica. Fig. 3. Eleocharis pellucida (inflorescences and stems)

References

Correll DS, Correll HB (1975). Aquatic and wetland plants of Southwestern United States (2nd ed.). Stanford University Press, Stanford. DAISIE (2008) Handbook of alien species in Europe. Invading Nature: Springer Series in Invasion Ecology 3. Springer. Author Lastrucci L, Becattini R (2007) Eleocharis carniolica Koch (Cyperaceae) nuova per la Toscana (Italia Centrale) e distribuzione delle specie correlate. Webbia 62(1): 11‐26. VERLOOVE, Filip. Lonati M, Gorlier A, Ascoli D, Marzano R, Lombardi G (2009) Response of the alien species Panicum acuminatum to disturbance in an Italian lowland heathland. Bot. [email protected] Helv. 119: 105‐111. Pyke S (2008).Contribución al conocimiento de la flora alóctona catalana. Collect. Bot. National Botanic Garden of 27: 95‐104. Belgium, Domein van Pyšek P (2003) How reliable are data on alien species in Flora Europaea? Flora 198: 499‐ 507. Bouchout, B‐1860 Meise, Randall RP (2002) A Global Compendium of Weeds. RG and FJ Richardson, Meredith, Belgium Victoria, 906 pp. Open access at www.hear.org/gcw/ Verloove F (2006) Catalogue of neophytes in Belgium (1800‐2005). National Botanic Garden of Belgium, Meise (Scripta Botanica 39): 89 p. Copyrights 2010 owned by The Verloove F (2008) Studies within the genus Digitaria Haller (Poaceae, Panicoideae) in Authors southwestern Europe. Candollea 63: 227‐233. Verloove F (2010) Studies in Italian Cyperaceae. 1. Eleocharis pellucida, new to Europe, naturalised in Piemonte. Webbia 65(1) (in press) Verloove F, Lambinon J (2008) Neophytes in Belgium: corrections and adjustments. Systematics and Geography of Plants 78: 63‐79. Verloove F, Sánchez Gullón E (2008) New records of interesting xenophytes in the Iberian Peninsula. Acta Botanica Malacitana 33: 147‐167.

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