Rumex tunetanus Barratte & Murbeck ex Murbeck (1899: 5)

Ghrabi-Gammar, Zeineb, Muller, Serge D., Rouissi, Maya, Jilani, Imtinen Ben Haj, Rhazi, Laïla, Bélair, Gérard De, Saad-Limam, Semia Ben & Daoud-Bouattour, Amina, 2017, Rumex tunetanus (Polygonaceae): rediscovery of an endangered Tunisian endemic, Phytotaxa 296 (2), pp. 118-130 : 121-125

Rumex tunetanus Barratte & Murbeck ex Murbeck (1899: 5)

Type (lectotype designated here): mission botanique de Tunisie, bords du lac Cejnan, Kroumirie orientale , 23 June 1888, Cosson, Barratte & Duval s.n. (P-05338611!, image of the lectotype available at http://mediaphoto.mnhn.fr/media/ 1441386044455s2QUltcOdjvT6n 2t; isolectotype P-05338612!, image of the isolectotype available at http://mediaphoto. mnhn.fr/media/1441386044474 M1 oZVHh7XfuUEtr0) .

Description ( Fig. 2 ): — perennial, amphibious geophyte, with a tuberous vertical, thick, dark-brown taproot topped off with 1 – 4 short rhizomes, each developing an aerial axis. Stem erect, 80 – 120 cm tall, thin, reddish, striped, with 8 – 10 internodes (basal internode reaches 25 cm in length). Basal leaves petiolate (petiole about 18 cm long, and slightly enlarged at the base), with blade 18 – 20 cm long, ridged, more or less cordate at the base; cauline leaves similar to the basal one but smaller in size. Inflorescence branched 4, in the upper half of the stem, each consisting in a loose leafless panicle. 15 flowering whorls, the lower ones spaced (distance between two successive whorls 2.0 – 2.5 cm) and bearing about 25 flowers, the upper whorls more densely arranged (0.5 cm) and with 3 – 5 flowers. Outer sepals pinkish, linear and adpressed on the edges of fruit-bearing valves that are triangular, densely reticulated by barely bulging veins, with 5 – 8 shallow pairs of uneven, slightly curved teeths (5 – 6 or 4 – 6 mm long), with an oblong-ovoid callosity (equal to or longer than half the valve length), the two lateral leaves are shorter and have smaller callosities; anthers, which are as long as the fruit-bearing valves, become flat and large with curved edges after pollen release. After fertilization, each flowering axis can release between 400 and 600 brown, shiny achenes (2.7 – 3.0 mm long with a maximum width at the middle). Pollen grain subsphaerical (30 – 35 μm in diameter), micro-cross-linked, tricolporate, with thin, long furrows (ectoapertures) and small, round pores (endoapertures).

Typification:— Baratte & Murbeck (1899: 5) described Rumex tunetanus through a short diagnosis: “ is mostly characterized by stem leaves which are quite narrow, very elongated, more or less highly corrugated and stiff in the edges, more or less deeply cordate at the base where the limb reaches its biggest width ”; they also provided an illustration which is part of the original material. In the protologue, R. tunetanus was considered to be related to the sympatric R. crispus , and R. stenophyllus Ledebour (1830: 58) . Baratte & Murbeck (1899: 5) also cited two specimens (syntypes according to the Art. 9.7 of ICN, McNeill et al. 2012) collected in 1888 during the last botanical mission of the Committee Responsible for the Scientific Exploration of Tunisia. We found these two specimens at P (codes 05338611, and 05338612), both bearing plants whose features matches the diagnosis. We here designate the P-05338611 as the lectotype of the name Rumex tunetanus , while the P-05338612 is the isolectotype.

Chromosome number:— Unknown.

Habitat and ecology:— Rumex tunetanus grows on temporary habitats ( Fig. 3 A ) characterized by sandy-silty soils at water depths of 20 – 50 cm during the flooding period [marshes of the ancient lake of Sejenane ( Fig. 1 ; see also Gauthier-Lièvre 1931, Pottier-Alapetite & Labbe 1951, Pottier-Alapetite 1958)]. This particular wetland was comparable to the large lakes of NE-Algeria ( Samraoui & de Bélair 1997, Stevenson et al. 1998, Rouissi et al. 2016) before it was seriously damaged by the various water projects between 1958 – 1980 (digging drainage ditches, drilling wells, building dams on the Sejenane River, etc.) and, perhaps, by drought between 1980 – 2002 ( Ouali et al. 2014).These disturbances have led to the partition of the garâa and to its transformation into a patchwork of temporary habitats and cultivated lands that have resulted in a reorganisation of hydrophytic plant communities and the extinction of the most of vulnerable species. Today, the area is mainly used for grazing, fodder (sorghum), summer crops (tomato, pepper, watermelon, melon, tobacco) and off-season crops (potato, green beans) (I. Ben Haj Jilani, unpublished data).

The communities including Rumex tunetanus thus appear to be temporary habitats somewhere between marshes and ponds, with a physiognomy of marshes related to the occurrence of high perennial helophytes but sheltering a number of annual species which are typical of temporary ponds. Both sites have higher water depths (from 30 to 50 cm in winter) that are entirely mown in summer; the 4 other sites are grazed in spring. They have apparently never been cultivated, probably because of their late submersion until the end of spring. The water pH is slightly acid (6.7), and the sandy-silty soils (2/3 sand, 1/3 silt and clay) contain 16.3 % of organic matter and 2.7 % of carbonates.

Our phytoecological study shows that the habitat dominated by the longest hydroperiod seems the most favorable: R. tunetanus occurs in dense populations within helophytic vegetation including species such as: Bolboschoenus glaucus ( Lamarck 1791: 142) S.G. Smith (1995: 101) , Helosciadium crassipes W.D.J. Koch ex Rchb. (1824: 16) , Oenanthe fistulosa Linnaeus (1753: 254) and O. silaifolia M. Bieb. (1819: 232) . Shallower habitats with shorter hydroperiods show lower densities, with plant communities including numerous species of temporary ponds [particularly, Isoetes velata , Myosotis sicula Gussone (1843: 214) and Pilularia minuta ]. This difference suggests that R. tunetanus is sensitive to the nature and intensity of disturbances, and that it endures late mowing (June; Fig. 3 B ) better than spring grazing, which may be attributed both to the preservation of its sexual reproduction and to its capacity for vegetative regeneration by rhizome fragmentation.

Despite these drastic changes, traditional agro-pastoral practices such as summer mowing of wet meadows and marshes, have preserved a rich biodiversity, particularly concerning that of the plant communities with Rumex tunetanus . Local agricultural practices are rapidly evolving, however, and significant projects (dam, roads…) are ongoing or planned for the near future so as to open the region up and encourage its economic development (Ferchichi-Ben Jamaa 2010). The population growth that will follow these changes will surely put growing pressure on the already weakened, fragmented wet habitats and most likely threaten R. tunetanus .

Distribution:— Rumex tunetanus is the only Tunisian endemic belonging to the genus Rumex (see e.g., Le Floc’h et al. 2010), with a distribution are restricted to Garâa Sejenane (area ranging from 500 m 2 to 30 ha).

Taxonomical notes:— Rumex tunetanus is morphologically similar to R. algeriensis var. hipporegianus , and R. crispus . Murbeck (1899) compared R. algeriensis with R. tunetanus from the morphological point of view showing similarities “ especially in its quite narrow, very elongated stem leaves which are more or less deeply cordate at the base where the limb reaches its biggest width ”, but distinguishing R. tunetanus by “ its full length heavily ridged rod, by its thicker panicle, by its multiflorous look like whorls, by its longer and more twig-like pedicles, by its fuller more narrow valves, by its callus which length does not generally reach half of that of the valves, by the caryopse having its biggest width in the middle, etc. ”.

Phytosociological remarks:— The phytosociological data reveal the occurrence of 58 species (Table 1), of which 70 % are strictly associated with wetlands ( Ghrabi-Gammar et al. 2009). Based on the result of the correspondence analysis (CA; Fig. 4 ), plant communities with R. tunetanus refer to temporary habitats (temporary marshes, flooded crops and temporary ponds). These communities include many helophytes [ Alisma lanceolatum Withering (1796: 362) , Alopecurus bulbosus Gouan (1762: 37) , Bolboschoenus glaucus , Cyperus longus Linnaeus (1753: 45) subsp. badius ( Desfontaines 1798: 45) Bonnier & Layens (1894: 324) , Eleocharis palustris ( Linnaeus 1753: 47) Roemer & Schultes (1817: 151) , Helosciadium crassipes , Juncus heterophyllus Dufour (1825: 88) , Oenanthe fistulosa , O. silaifolia , O. virgata Poiret (1798: 529) , Rumex pulcher Linnaeus (1753: 336) ] as well as typical amphibious species of temporary Mediterranean pools [such as Elatine macropoda Gussone (1827: 475) , Eryngium pusillum , Isoetes velata , Juncus capitatus Weigel (1772: 28) , J. pygmaeus Richard ex Thuillier (1799: 178) , Lythrum borysthenicum ( Schrank 1822: 643) Litvinov (1917: 209) , L. hyssopifolia Linnaeus (1753: 447) , L. tribracteatum Salzmann ex Sprengel (1827: 190) , Myosotis sicula , Pilularia minuta , Ranunculus baudotii Godron (1840: 21) , R. ophioglossifolius Villars (1789: 731) , R. sardous Crantz (1763: 84) ]. Two populations of R. tunetanus occur on the CA graphs in the temporary ponds ( Fig. 4 ), showing a species tolerance to summer drying out. Communities with R. tunetanus have maximum densities of 150 plants/ha for the most extensive population (GS1), and densities of 5–30 plants/ha for other populations.

Conservation status:— Any assessment appears to be defined at present. The conservation of Rumex tunetanus requires the protection of its habitat and the continuity of current traditional agro-pastoral practices that appear to be compatible with its preservation. The most urgent measures include: 1) the legal protection of the species by adding it to the national list of protected species, 2) the survey of existing populations, 3) the acquisition of all or parts of the fields where the species grows (state property) or setting up management conventions with owners, 4) the preservation of traditional agro-pastoral activities that are compatible with the species conservation, 5) raising the awareness of local inhabitants about the importance of safeguarding wetlands, and their involvement in and contribution to their conservation, and 6) the implementation of ex-situ conservation measures of the species (Genes Bank) by preserving ripe fruit picked during the summer before mowing and species cultivation in suitable wet areas.

On the basis of the distribution of Rumex tunetanus , which is limited to a few hectares, and the threats to its habitat, this Tunisian steno-endemic is listed as Critically Endangered (B1ab(ii,iii)+2ab(ii,iii), IUCN 2008; see also García et al. 2010, Rhazi et al. 2010). The Garâa Sejenane has recently been designated as the first Important Plant Area in Tunisia ( Radford et al. 2011).

Specimen examined: — TUNISIA. Garâa Sejenane , “mission botanique de Tunisie, bords du lac Cejnan, Kroumirie orientale ”, 23 June 1888, Cosson, Barratte & Duval s.n. (P-05338611!) ; Garâa Sejenane , “mission botanique de Tunisie, bords du lac Cejnan, Kroumirie orientale ”, 23 June 1888, Cosson, Barratte & Duval s.n. (P-05338612!) ; Garâa Sejenane , Tunisia, 26 May 2009, Ghrabi-Gammar, Daoud-Bouattour & Muller ( INAT!) ; Garâa Sejenane , 02 November 2009, Ghrabi-Gammar, Daoud-Bouattour & Muller (Herb. SDM) ; Garâa Sejenane , 05 May 2014, Ghrabi-Gammar, Daoud-Bouattour & Muller ( INAT!) .

Figures

FIGURE 1. Location of Garâa Sejenane (Google earth V 7.1.7.2606). The ancient lake is represented in dots. The photograph shows Garâa Sejenane viewed from the south (photo by A. Daoud-Bouattour, February 2010): the central zone of the plain is cultivated and grazed, and the surrounding hills are covered with degraded cork-oak woods.

FIGURE 2. Rumex tunetanus: A, habitus; B, basal leaf; C, tuberous taproot; D, flowers showing stamens; E, fruit surrounded by three serrated valves; F, 3-angled achenes, with one bearing a dried style; G, tricolporate pollen grains. Scales: A–C, 1 cm; D–E, 5 mm; F, 1 mm; G, 20 μm (drawings S.D. Muller & Z. Ghrabi-Gammar, photo S.D. Muller).

FIGURE 3. GS1: A, temporary marsh with Rumex tunetanus during a high-water period (photo by S.D. Muller, 03 October 2009); B, production of hay fodder by local inhabitants during summer (photo by A. Daoud-Bouattour, 12 July 2010).

FIGURE 4. Correspondence analysis (CA) performed on the 176 species and 52 relevés, including 45 relevés from 36 regional wetlands (Ferchichi-Ben Jamaa et al. 2010) and 7 samples carried out between 2009 and 2014 in populations of Rumex tunetanus. Axes 1 and 2 represent respectively 7.92% and 6.96% of the total variability.