Hardion, L., R. Verlaque, M. W. Callmander & B. Vila (2012). Arundo micrantha Lam. (Poaceae), the correct name for Arundo mauritanica Desf. and Arundo mediterranea Danin. Candollea 67: 131–135. In English, English and French abstracts.
Arundo micrantha Lam. (Poaceae) was validly published by Lamarck in 1791 but has been overlooked in the literature. Based on recent taxonomic and phylogenetic studies, this name is rehabilitated to designate a circum-Mediterranean taxon, with Arundo mauritanica Desf. and Arundo mediterranea Danin as later synonyms. For the first time, Arundo micrantha is recorded in the Flora of France based on two rediscoveries (Golfe-Juan and Ste-Lucie Island) and identifications in the wild, thanks to indications of older specimens in herbaria G, MARS, MPU and P. However, these two populations of Arundo micrantha are under severe threats and this species must be considered as Critically Endangered in France following IUCN Red List Categories.
Introduction
Before 2004, three distinct species were included in the genus Arundo L. (Poaceae): (1) A. donax L., the cosmopolitan Giant Reed from Sub-tropical Asia to the Mediterranean Basin, introduced in many regions; (2) A. formosana Haeck., a decumbent grass endemic from Taiwan, and (3) A. plinii Turra, a circum-Mediterranean taxon. Arundo plinii was revisited by Danin (2004) and divided into three entities : (a) A. plinii s.s., a sub-endemic taxon from Southern France (Var: Fréjus; Aude: Sainte-Lucie Island) and northern Italy (Bologna: locus classicus following Turra, 1780); (b) A. collina Ten., an Italo-Balkan Arundo described from Naples (Tenore, 1822), and (c) A. mediterranea Danin (locus classicus : Nahal Sorek, Israel, following Danin, 2004), a new species corresponding to a branched reed from Algeria, Cyprus, Greece and Palestine.
On the basis of Art. 53.1 of the International Code of Botanical Nomenclature (ICBN) (McNeil & al., 2006), Danin (2004) published the new species A. mediterranea in order to replace A. mauritanica Desf. described from Algeria by Desfontaines (1798). In fact, this latter name is an illegitimate homonym of A. mauritanica previously used by Poiret (1789) to describe a species actually named Ampelodesmos mauritanicus (Poir.) T. Durand & Schinz (Durand & Schinz, 1895). However, Desfontaines had distributed many duplicata of his Algerian collection among European herbaria such as P, B, G, K and MPU. One of these exsiccata was given to his friend Jean-Baptiste de Lamarck, as mentioned both on the label and the diagnosis (“D. Desfontaines” [D. = Dedit], “ill. gen.” [= “Illustration des Genres”]; Fig. 1 and 2). On the basis of this specimen, Lamarck (1791) described A. micrantha Lam. (Fig. 2), seven years before the publication of Desfontaines (1798). Strangely, Lamarck's name has been overlooked over the past centuries, and this binomial was generally considered as a synonym of A. mauritanica Desf. under A. plinii s.l.
A recent molecular phylogenetic study based on AFLP markers showed that all considered samples of A. micrantha are clearly monophyletic and belong to a well supported species (Mariani & al., 2010; as A. mediterranea). DNA content analysis by flow cytometry and chromosome counts confirmed this singularity. In fact, this taxon exhibits a specific chromosome number of 2n = ca. 72 (North-Africa and Crete) vs 2n = 76 for A. plinii from Italy (Hardion & al., 2011). This chromosome number has been recently confirmed for various other populations from several Mediterranean countries (unpublished data).
Following Art. 11.4 of ICBN, A. micrantha remains the prevalent name of this species attached to the holotype housed in Lamarck's Herbarium (P-LA). Considering that A. micrantha and A. mauritanica are not based on the same holotype, the latter must be considered as synonym of A. micrantha (see Art. 8.1, 52.1 and 52.2 of ICBN). It is nevertheless impossible to know if they belong to the same gathering and we therefore consider isotypes of each taxon as hypothetical.
Taxonomy and nomenclature
Arundo micrantha Lam., Tabl. Encycl. 1: 196. 1791 (Fig. 1).
Typus: “Ex Africa”: Desfontaines s.n. (holo-: P-LA [P00564266]!; iso-: B [W02223]!, G [G00074067]!, K [K000366972]!, MPU [015598]!, P [P00307101]!).
= Arundo mauritanica Desf., Fl. Atlant. 1: 106. 1798 [non Poir., Voy. Barbarie 2: 104. 1789. ≡ Ampelodesmos mauritanicus (Poir.) Durand & Schinz]. Typus: Algeria: “Herbier de la Flore Atlantique”, Desfontaines s.n. (holo-: P [P00307101]!; iso-: B [W02223]!, G [G000 74067]!, K [K000366972]!, MPU [015598]!, P-LA [P00564266]!).
= Arundo mediterranea Danin in Wildenowia 34: 362. 2004. Typus: Israel: Nahal Sorek, 8 km east of Gedera, 18.IX.2004, Danin s.n. (holo-: HUJ!; iso-: B [1001 822322, 100182323]!, E [00205435]!, MARS [00007, 00008]!).
Additional specimens examined. — France. Languedoc-Roussillon: Sainte Lucie, Requien s.n. (MARS-Ardoino [00011]); Aude, Coteau à Sainte-Lucie, près de Narbonne, 21.IX.1818, Gautier s.n. (G-DC); Sainte-Lucie, 19.V.1828, Requien s.n. (G); In insula St Luciae, X.1829, Eudrefs s.n. (P [P03161112, P03161120]); Ile Sainte-Lucie, près de Narbonne, 25.VIII.1864, Gautier s.n. (MPU, P [P03626575]); Ile Sainte-Lucie, 12.IX.1877, Bonneau s.n. (MPU); Ile Sainte Lucie, près de Narbonne, molasse marine, 15 m, 27.IX.1882, Doumergue s.n. (G, MARS [00012], MPU, P [P02656180, P02656198, P03161077, P03235090, P03626594]); Sainte-Lucie, 1891, Requien s.n. (MPU); Aude, Ile Sainte-Lucie, IX.1893, Jonas-Martyr s.n. (G, MPU, P [P02421019, P02421020, P02421021, P03161074, P03168006, P03235087, P03626559, P03626580]); Ile Sainte-Lucie, IX.1893, Martin s.n. (P [P03626574]); Ile Sainte-Lucie, IX.1893-94, Sevitien & Sevitien s.n. (G, MPU, P [P02421022, P03161075, P03235086, P03242364, P03242365, P03235079, P03626551, P03626552, P03626579]); Aude, Ile Sainte-Lucie, près de la station de chemin de fer, 20.II.1921, Neyraut s.n. (MPU); Port-la-Nouvelle, Ile Sainte-Lucie, between the island and railway, ca. 2 m, 43°03′25″N 03°01′52″E, 5.VIII.2011, Hardion & al. s.n. (MARS [00013], MARS [00014]). Provence-Alpes-Côte d'Azur: entre Cannes et Antibes, dans le Golfe de Juan, Gay s.n. (MPU); Golfe de Juan, 24.IX.1821, Gay s.n. (G); Route d'Antibes à Cannes, devant la villa “Jean Reynaud”, 10.X. 1868, Thuret s.n. (G); Golfe-Juan, 28.X.1868, Moggridga s.n. (P [P03626544]); Golfe-Juan, bords des ravines, 31.X. 1868, Thuret s.n. (G, P [P03161108]); Golfe Juan, non loin de la gare, presque en face du Château Robert, 27.X.1874, Bernardin s.n. (G, MPU, P [P02420203, P02656199, P03161104, P03626 558]); Golfe-Juan, 5.XI.1878, Consolat s.n. (G); Golfe-Juan, XII.1904, Mader s.n. (G); Vallauris Golfe-Juan, in beach back, between road and railway, ca. 4 m, 43°33′48″N 7°04′07″E, 21.IX.2011, Hardion & al. s.n. (MARS [00015], MARS [00016]).
Morphology. — Our observations in the wild confirmed that A. micrantha is characterized by clearly branched stems, as previously emphasized by Desfontaines (1798) and Danin (2004), coupled with a tussock habit and high culms (2–4 m) as described by Danin (2004). However, these features are rarely present on herbarium specimens. On exsiccata, A. plinii complex (including A. micrantha) differs from A. donax by its spikelets with 1-(2) vs 3–5 flowers as mentioned by Lamarck (1791). Moreover, our study on many herbarium exsiccata (G, MARS, MPU, P) shows that A. micrantha differs from the rest of A. plinii complex by a larger culm diameter under the panicule (> 5 mm vs < 4 mm). This new morphological character allows us to consider A. micrantha holotypus of Lamarck as conspecific with A. mauritanica Desf. and A. mediterranea Danin.
However, a broad morphological investigation coupled with a phylogenetic analysis on a Mediterranean sampling is needed to clarify the complex taxonomic delimitations in this genus. Because of many erroneous identifications in Herbarium exsiccata, this study will have to provide more discriminating characters, useful on vegetative as well as on reproductive material.
Ecology, distribution and conservation. — Notes on exsiccata labels gave us insights into the ecology of A. micrantha and its affinities with wetlands. This species mainly occurs on riverbanks and beach backs, in addition to ruderal sites. Because of its former synonymy under A. plinii s.l. and its resemblance to A. donax, the A. micrantha distribution was dramatically underestimated in the Mediterranean basin. Since 2004, it has been reported from Algeria, Crete, Cyprus, Greece, Lebanon, Morocco, Palestine and Rhodes (Danin, 2004; Dobignard & Chatelain, 2010). The careful examination of several specimens of A. plinii s.l. (G, MARS, MPU and P) allowed us to rediscover and identify wild populations in Golfe-Juan (Provence-Alpes-Côte d'Azur) and Sainte-Lucie Island (Languedoc-Roussillon) as A. micrantha. This discover adds for the first time this species to the Flora of France, in addition to A. donax and A. plinii (sensu Danin, 2004) from Fréjus-Saint-Raphaël. Our field observations of these restricted populations revealed their highly threatened status. In Golfe-Juan, two patches (10 m2) subsist on the urban littoral of French Riviera, between the back beach road and the railway, endangered by a project to extend train rails. According to numerous exsiccata, the population of Sainte-Lucie Island was the most visited of the French localities. Already impacted by human activity in the 19th century (as indicated on P [032 42232]), this population is now drastically reduced to 4 m2, without flowering for at least three years. In addition, other localities of A. plinii s.l. as Salses-le-Château (Languedoc-Roussillon) and Saint-Tropez (Provence-Alpes-Côte d'Azur) respectively mentioned by Gautier (1912–1913) and Camus & Camus (1912), have never been seen again. Armando plinii s.l. being protected at regional scale (Provence-Alpes-Côte d'Azur and Languedoc-Roussillon), A. micrantha must be included under this status. However, A. micrantha needs urgent specific protection on French territory and may be considered as Critically Endangered (CR A1a, c; C1; D) in France following IUCN Red List Categories and Criteria (IUCN, 2001).
Acknowledgements
The authors would like to thank Olivier Argagnon, Katia Diadéma, Henri Michaud, James Molina and Virgile Noble from the Conservatoire Botanique National Méditerranéen de Porquerolles for their help in field. The authors are also grateful to Marc Pignal (P) and Nick Turland (MO) for clarifying the nomenclatural issue, and MPU staff who provided us helpful information regarding several exsiccata. Financial support was provided by grants from the ECCOREV research federation, PIRVE “Canne de Pline” from the CNRS, the “Ministère d'Ecologie, du Développement Durable, des Transports et du Logement” and the “Société Botanique de France”. Valuable comments of an anonymous reviewer greatly improved our manuscript.
