ACTA BOT. CROAT. 78 (1), 2019 91 Acta Bot. Croat. 78 (1), 91–94, 2019 CODEN: ABCRA 25 DOI: 10.2478/botcro-2018-0009 ISSN 0365-0588 eISSN 1847-8476 A new addition to the alien flora of Tunisia, Amaranthus spinosus L. (Amaranthaceae s.l.), with notes on A. diacanthus Raf. Duilio Iamonico1*, Ridha El Mokni2,3 1 University of Rome Sapienza, Department PDTA, Section Environment and Landscape, via Flaminia 72, 00196 Rome, Italy 2 Laboratory of Botany and Plant Ecology, Faculty of Sciences of Bizerta, University of Carthage, Jarzouna-7021, Bizerta, Tunisia 3 Faculty of Pharmacy of Monastir, University of Monastir, BP. N° 207, Avenue Avicenna, Monastir-5000, Tunisia Abstract – Amaranthus spinosus L. (Amaranthaceae s.l.), a species native to the Neotropics, has been found in four localities (Bizerta, Bir Bouregba, Hammamet, and Nabeul) of N. Tunisia. Our discovery represents the first record at national level, and the second one for N. Africa. Morphological characters and ecological data are given. Nomencla- tural notes are provided for the name A. diacanthus, which was regarded by some authors as heterotypic synonym of A. spinosus. A neotype is designated in the present paper based on a specimen preserved at LSU. Keywords: alien species, Amaranthus, neophyte, typification * Corresponding author, e-mail: d.iamonico@yahoo.it Introduction The genus Amaranthus L. (Amaranthaceae Juss.) com- prises about 70 mostly annual, monoecious and dioecious species, of which approximately 40 are native in America (see e.g., Costea et al. 2001, Iamonico 2015a). Some species of Amaranthus are used as ornamentals and are able to es- cape from cultivation, having an economic impact mainly on agricultural systems (reduction of productivity and crop quality), while other taxa have an ecological impact on native flora and vegetation [e.g. A. tuberculatus (Moq.) J.D.Sauer in a riparian habitat] (see e.g., Iamonico 2015b). The infrage- neric classification of Amaranthus still remains unresolved, lacking a comprehensive molecular study (see e.g., Hernán- dez-Ledesma et al. 2015). On the basis of morphology and chorology, Mosyakin and Robertson (1996) recognized three subgenera: subg. Acnida (L.) Aellen ex K.R. Robertson with three sections, subg. Albersia (Kunth) Gren. et Godr. with four sections, and subg. Amaranthus, with three sections and two subsections. According to Mosyakin and Robert- son (1996: 278), Amaranthus spinosus L. is the only species belonging to Amaranthus subg. Amaranthus sect. Centrusa Griseb. The Flora of Africa (see SANBI 2012 and literature there- in, Iamonico 2015c and literature therein) currently includes Amaranthus spinosus, which is recorded in many countries of central and southern parts of the continent, while in the north it occurs only in Egypt. As part of an ongoing no- menclatural and taxonomic study on the genus Amaranthus (see e.g., Iamonico 2014a, 2014b, 2015a, 2015c, 2016a, 2016b, 2016c, Iamonico and Das 2014) and the Tunisian Amaran- thaceae s. lat. (see e.g., Iamonico and El Mokni 2017, Suk- horukov et al. 2016), some populations have been found that certainly refer to A. spinosus. The number of Tunisian Ama- ranthus species has thereby been increased, since this find- ing represents the first record for the Flora of Tunisia and the second for the Flora of N. Africa. Moreover, the name Ama- ranthus diacanthus, which some authors suggest be regard- ed as a synonym of A. spinosus (e.g., Rojas-Sandoval 2015, Wunderlin et al. 2017), is here investigated from the nomen- clatural point of view, as it is still untypified. Materials and methods The work is based on an extensive analysis of literature, and examination of the specimens kept in the Herbaria FI, HFLA, LINN, LSU, and RO (acronyms according to Thiers 2019+), and in the Herbarium of the Faculty of Pharmacy of Short communication IAMONICO D., EL MOKNI R. 92 ACTA BOT. CROAT. 78 (1), 2019 Monastir and of the Faculty of Sciences of Bizerta (not listed in Index Herbariorum), where the personal collections of R. El Mokni are kept. The articles cited through the text agree with the Shenzen Code, ICN (Turland et al. 2018). Results and discussion Nomenclatural notes on Amaranthus diacanthus Rafinesque (1817: 31–32) described A. diacanthus and provided a short diagnosis. Rafinesque (l.c.) also cited the Flore Louisinaise by Robin (1807). The latter author (Robin 1807: 372) listed an Atriplex taxon, but he did not report any epithet. As a consequence, Rafinesque (l.c.), probably on the basis of the detailed description made by Robin (l.c.), pro- posed the plants occurring in Louisiana (S-USA) as a new species. We have not been able to trace Rafinesque’s materi- al, which could be useful for typification purposes. We loo- ked at material collected by C. C. Robin in Louisiana, which could be observed and used by C. S. Rafinesque, to describe A. diacanthus. Unfortunately, no Robin specimen was traced [moreover, Stafleu and Cowan (1985: 812) reported “Herba- rium and Types: Unknown”]. Since no original material se- ems to be extant, no lectotype can be designed, and neotypi- fication is required (see Arts. 9.2, 9.3, and 9.7). Accordingly, we selected a specimen preserved at LSU (catalog number 83081) and collected in Louisiana, in Webster County. The LSU-83081 is here designated as the neotype of the name Amaranthus diacanthus. Concerning the identity of A. diacanthus, note that the diagnosis by Rafinesque (1817) and the description of Atriplex sp. made by Robin (1807) include an important morphological character [“...glomerulis bispinosis...” by Ra- finesque (1807), and “...les paques de fleurs des sisselles ac- compagnés de deux épines divergentes...” by Robin (1807)]: the occurrence of a spine-like feature at the bases of the flo- ral glomerules [according to Costea and Tardif (2003) the- se structures are actually the bracts of the first flower in the first cyme of the glomerule which metamorphoses in the ear- ly phase of the onthogeny]. This structure was the basis for the selection of the neotype, representing a unique feature in the genus Amaranthus, characterizing the species currently known as A. spinosus (see e.g., Bojian et al. 2003, Mosyakin and Robertson 2003, Iamonico 2015a). As a consequence, these two names can be treated as heterotypic synonyms, the Linnaean having nomenclatural priority (1753 vs. 1817). Taxonomic treatment Amaranthus spinosus L., Sp. Pl., 2: 991. 1753. Lectotype (designated by Fawcett and Redle 1914: 103): Herb. Linnaeus, no. 1117.27 (LINN!). Image of the lectotype available at http://linnean-online.org/11653/). = Amaranthus diacanthus Raf., Fl. Ludov.: 31-32. 1817. Neotype (here designated): U.S.A., Louisiana, Webster County, Camp Minden, 1.2 km E of Jim Davis Cemetery, 0.3 km NW of Richardson Cemetery, 14 July 2003, L. Blay, T. Pazzaglia et N. Hastings 906 (LSU-83081!). Image of the neo- type available at http://data.cyberfloralouisiana.com/lsu/). Description – Herbs 6–15 dm tall, monoecious, annual (therophyte). Stems erect, glabrous brownish, branched. Le- aves green to reddish (on the upper surface), ovate to lanceo- late, rhomboidal [(2.0–)2.5–6.5(–7.5) × (1.0–)2.5–4.0(–3.5) cm], with entire margins, apex obtuse or acute, mucronate, base cuneate, glabrous, petioled (petiole 1.5–8.5 cm long), associated to 2 spine-like structures (modified bracts), 7.0– 8.0 mm long. Synflorescences terminal, panicle-like, the main florescence up to 15 cm long, usually green and axillary glomerules. Floral bracts lanceolate (3.0–4.0 × 0.5−1.0 mm) as long as or shorter than the perianth, acute, awned, mar- gin entire, glabrous. Staminate flowers with 5 tepals, ovate- lanceolate; stamens 5. Pistillate flowers with 5 tepals, lanceo- late–spathulate (3.5–4.0 × 0.9–1.0 mm), with usually obtuse and mucronate apex; stigmas 3–4. Fruit brown or yellow- ish, ellipsoidal (2.0–2.1 × 1.4–1.5 mm) as long as or slightly shorter than the perianth, smooth below, rugose on top, de- hiscent. Seed lenticular (about 0.9 mm in diameter), brown. Phenology – Flowering and fruiting time October-De- cember. Habitat – Roadsides, public gardens, and cultivated areas with trees (e.g. Citrus sp.), at 6–41 m a.s.l. Fig. 1. Habit of Amaranthus spinosus L. (bar = 1 cm) at Nabeul region in Tunisia with detail of spine-like structures (left corner; bar = 4 mm) (photos by R. El Mokni). AMARANTHUS SPINOSUS IN TUNISIA ACTA BOT. CROAT. 78 (1), 2019 93 Distribution in Tunisia – Four populations (16-18 in- dividuals in total) were found in the following localities: Bizerta [three individuals (each about 150 cm tall) cover- ing an area of 9 m2], Bir Bouregba [two individuals (each about 70 cm tall) covering 2 m2], Hammamet [three-four individuals (each about 90 cm tall covering 4 m2], and Na- beul [eight-nine individuals (each about 60 cm tall) cov- ering 25 m2]. Native range and status of naturalization in Tunisia – A. spinosus is a neophyte species native to the Neotropics, while it is an alien in many countries of Europe (Iamonico 2015c), C. and S. Africa (Sanbi 2012), N. and E. Australia (Atlas Liv- ing of Australia 2016), and Asia (see e.g., Townsend 1974, Bojian et al. 2003). Concerning N. Africa, this species was previously recorded only in Egypt (see Boulos 2009: 56, Ia- monico 2015c). The four populations of A. spinosus discovered in Tuni- sia (see above “Distribution in Tunisia”) were observed from 2012 to 2016. Although the plants seem to self-replace with- out direct human intervention, we prefer to consider A. spi- nosus as casual alien species in Tunisia at the moment. Chromosome number – A. spinosus is a diploid species with 2n = 34 (see e.g., Greizerstein and Poggio 1992, Song et al. 2002, Sheidai and Mohammadzdeh 2008). Specimina visa – Tunisia: Bizerta (North-Bizerta, Cor- niche), 37°19'31" N, 09°51'52" E, uncultivated land, 06 m a.s.l., 27 October 2013, R. El Mokni (HFLA, Herb. Univ. Bizerta); Nabeul (North-Nabeul, Cap-Bon), 36°26'26" N, 10°42'25" E, roadsides, 08 m a.s.l., 09 December 2015, R. El Mokni (Herb. Univ. Monastir); Nabeul (North-Hamma- met, Cap-Bon), 36°24'35" N, 10°36'06" E, cultivated land, 22 m a.s.l., 10 December 2016, R. El Mokni (Herb. Univ. Monastir); Nabeul (Bir Bouregba, Cap-Bon), 36°25´39" N, 10°34'56" E, roadsides, 41 m a.s.l., 09 December 2015, R. El Mokni (Herb. Univ. Monastir). Acknowledgements Thanks to the Directors and Curators of all quoted of- ficial herbaria and colleagues who own the cited personal herbaria for their support during our visits, loan of speci- mens, photographs or for providing interesting information. References Atlas of living Australia 2016+: Amaranthus spinosus L. 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