Non-native shrubby species of Euphorbia ( Euphorbiaceae ) in Tunisia

El Mokni, R.: Non-native shrubby species of Euphorbia ( Euphorbiaceae ) in Tunisia. — Fl. Medit. 33: 17-29. 2023. — ISSN: 1120-4052 printed, 2240-4538 online. Botanical surveys undertaken in several regions of Tunisia (N Africa), mainly around salty wetlands and flats and along railways since 2015, yielded new records of non-native shrubby plants of the genus Euphorbia . These included Euphorbia canariensis , E. cotinifolia subsp. coti-noides , E. cooperi var. cooperi , E. cyathophora , E. milii , E. pulcherrima , E. tirucalli and E. trigona . Among these records, three ( E. cotinifolia subsp. cotinoides , E. cooperi var. cooperi , and E. cyathophora ) are new for the non-native flora of the Mediterranean area, one for the non-native flora of the continental Africa ( E. canariensis ) whereas E. trigona and E. milii var. splen-dens are first reports to the non-native flora of N Africa. Moreover, Euphorbia pulcherrima is here assigned as first report for the non-native flora of the continental N Africa and E. tirucalli is confirmed as an established taxon and its distributive area is here updated. Distributions and brief morphological descriptions are given for each of these new records. Notes on their habitats and their main distinguishable features together with field photographs are also provided.


Introduction
In parallel to the increase of the industry of ornamental plants, flowering pot plants, flower bulbs and tree and nursery crops throughout the world, the rate of naturalizing plants is going faster and the number of naturalized/established (sometimes invaders) aliens is rising gradually in many countries worldwide.Within the Mediterranean area, in Europe (see e.g.Sanz Elorza & al. 2004; Capdevilla Argüelles & al. 2006; DAISIE 2009; Arianoutsou & al. 2010; Galasso & al. 2018; Domina 2021) as in many countries of N Africa (see e.g.Vilà & al. 1999; Meddour & El Mokni 2016; Sakhraoui & al. 2019; Meddour & al. 2020), the number of alien plant species is growing rapidly.Such alien flora includes a large number of families and genera where only 4 annual species were attributed to genus Euphorbia L. subg.Chamaesyce (Meddour & al. 2020).
Euphorbia, with around 1840 species distributed worldwide, is one of the most diversified Angiosperm genera of flowering plants (Esser & al. 2009; Horn & al. 2012; Riina & Berry 2012+).Euphorbia species occupy a wide range of habitats and exhibit great diversity growth forms including many kinds of prostrate, ascending, erect and small ephemeral

Material and Methods
Floristic field investigations carried out in Tunisia, mostly between 2015 and 2022, revealed new national records and even new records for N Africa and the Mediterranean area.Almost all taxa, observed in few (3-7) individuals, were not previously reported from either Tunisia, N Africa or sometimes the Mediterranean area.Records here reported are documented by a brief description of each taxon and infraspecific taxa, whenever present.Further comments on habitats of occurrence and taxonomic notes with closer or infraspecific taxa are also presented.For the identification and description numerous sources were consulted, mainly Eggli (2002), and the Encyclopedia of Succulents (2022) (retrieved from http://www.llifle.com/Encyclopedia/SUCCULENTS/Family/Euphorbiaceae/Euphorbia/).Reported taxa (species, and infraspecific taxa) are arranged alphabetically.Nomenclature is mostly in accordance with classifications of the Euphorbiaceae (see e.g.Bruyns & al. 2006; Bruyns 2012; Reveal 2012; Yang & al. 2012; Hassemer & al. 2017; Nobarinezhad & al. 2018; Tropicos 2022).

Results
Among the shrubby, succulent cacti-form and thorny species of Euphorbia, eight species are here reported for Tunisia belonging to two subgenera and five sections (subg.Chamaesyce with two sect.and subg.Euphorbia with three sect.).L. Sp. Pl. 1: 450. 1753.(Euphorbia subg.Euphorbia L. sect.Euphorbia L.) First report for the non-native flora of the continental Africa.Morphology (Fig. 1.F-G).Euphorbia canariensis is a small succulent shrub, 1 to 3(-4) m high.It clumps profusely from the base, one trunk may produce more than 150 branch-es; stems fleshy, stout, highly succulent, columnar, upright growing, deep green to reddish, 4 (rarely 5 or 6) angled up to 8 cm in diameter slightly spiraled; edges are obtuse and of a brown colour; spines dark shining in pair, perfectly regular, straight to cow-horn shaped; cyathium dark red to reddish-green, surrounded by an involucrum consisting of 1 leaf with 5 division, which have externally 5 glands alternating with them; male flowers naked monandrous, articulated with their pedicel surrounding the female, which is in the centre; female flowers naked solitary; ovarium stalked; stigma three forked; capsules maroon red on adult plants.First report for the non-native flora of the Mediterranean area as casual.Morphology (Fig. 2. A-C).A spiny, succulent tree that can reach 6-7 m in height; trunk is dark gray or brown and bears the scars of the old branches; branches thick, light green showing five to six ribs lined with pairs of black spines; leaves very small, rapidly caducous; inflorescence yellowish-green on the terminal segments; flowers yellowish green, small (4 mm) bisexual, sessile, arranged in 3 parallel rows along the ridges between the spines towards the tips of the branches, clustered in cymes each with by 3 cyathia with the male flowers at the tip in the centre of the row, and the bisexual flowers below on the outside; capsule large, 3lobed berry-like capsule, 15 × 8 mm long and green in colour with red markings that changes from red to purple when ripe throwing seeds away (Hyde & al. 2021) First report for the non-native flora the Mediterranean area as casual.Morphology (Fig. 1. C-D).An herbaceous to shrubby annual plant, erect to ascending, grows up to 1.50 m high, glabrous or loosely hairy, with multicellular hairs; stem is hollow, cylindrical with ribbed older, hollow, glabrous or sparsely pubescent, more or less yellow, containing a white latex.It bears leaves along its entire length or only at the apex in older plants; leaves are simple, stalked, the lower leaves alternate, while the upper leaves are opposite.The blade shape is variable.The terminal leaves are fully red or white colored; flowers are small and greenish-yellow, they are contained in small cups bearing on the edge, a small gland flattened bilobed; capsule is globose to three quarters out of the cup.(see more in Le Bourgeois & al. 2008).Distribution.With a native range from C USA to N Central Argentina, the plant was introduced in many countries all over the world but no report from N Africa and the Mediterranean area (POWO 2022b).

Euphorbia canariensis
Habitat in Tunisia.Euphorbia cyathophora was found as an alien (seven individuals in an area of 4 m 2 ) growing with native herbaceous plants in an oasis within the region of Douz, Kebili (SW Tunisia).Notes.Euphorbia cyathophora is almost similar to E. heterophylla L. from which it can be easily recognized by the color of the base of the bracts (often red to pinkish at base in E. cyathophora vs. completely green with the very base whitish in    First report for the non-native flora of the continental N Africa (and the Maghreb) as casual.Morphology (Fig. 1.E).A shrubby tree (up to 3 m tall); stem up to 8 cm in diameter, not to slightly branched; bark light brown, smooth; branchlets hollow; leaves alternate, green; stipules as small scales, caducous; petioles about 5-7 cm long, subglabrous; blades ovate-elliptic and sometimes panduriformly lobed, about 12-17 × 6-9 cm, chartaceous, base acute or obtuse with very base acute, margin entire, apex acuminate, glabrous above, slightly brighter and distinctly pubescent below, venation distinct, not triplinerved, with almost 16-17 pairs of sideveins; cyathia grouped in an apical pseudo-umbel, glabrous, their bracts enlarged, leaflike, with a pedicel of 1-3 cm, narrower than stem-leaves, green with red midrib or completely red; peduncles 4-5 mm long; involucres about 5 × 4-5 mm; gland only 1 about 5 mm wide, without appendage; ovary with a pedicel of c. 3 mm; stigmas united into a style column of 1-5 mm, free stigmas completely bifid; capsules not seen, described as green, sulcate, with a somewhat fleshy pericarp; seeds not seen, described as 10 mm long, smooth (Welzen & Chayamarit 2021).Distribution.Native to Mexican tropical forests from Sinaloa, W Mexico, to Guatemala (Steinmann, 2002), Euphorbia pulcherrima was vegetatively propagated as ornamental, known as a contemporary symbol of Christmas in many parts of the world (Ecke & al. 2004).The plant was reported as an alien in India and in the Canary Islands (Negi & Hajra 2007; APD 2022) and now widely cultivated in tropical and subtropical regions around the earth.In Europe as in continental North Africa, no report till now (Euro+Med 2006+; APD 2022).Habitat in Tunisia.Euphorbia pulcherrima was found along roadside on waste area in the region of Monastir (CE Tunisia).Notes.Euphorbia pulcherrima can be confused with E. cyathophora and E. heterophylla from which the plant differs mainly by its shrubby habit up to 3 m tall (vs.herbal habit up to 1.5 m tall for both E. cyathophora Murray and E. heterophylla), its cyathial bracts leaf-like, often deep red throughout (vs.uppermost leaves usually white in E. heterophylla or red in E. cyathophora at base only) and by its cyathia 4-5 mm in diameter (vs.cyathia less than 2 mm in diameter for both other species) (see e.g.Ma & Gilbert 2008; Silva & al. 2014) First report for the non-native flora of N Africa as casual.Morphology (Fig. 2. D-E).Succulent shrubs or trees; stems and branchlets 4-6 cm in diameter, indistinctly constricted into oblong segments to 10-25 cm long with three wing-like angles and carry short, divergent paired spines, reddish-brown, later dark up to 6 mm long; leaves lanceolate to drop-shaped, varying from 7 to 9 mm and deciduous, to 3-5 cm and more persistent; cyathia solitary or in groups, bracts paired to 3.5 × 4 mm, ovate, obtuse, dentate, glands 5 to 2.2 mm; bracteoles approximately 2.5 mm, obovate, apex fringed; stamens numerous, filaments jointed, 2.6 mm; female flowers erect, ovary about 3.7 mm across, 3-celled, style 3, ovule 1; capsule to 7 mm, 3-lobed, 3.5 mm, obovoid (cf.India Biodiversity Portal 2016).Distribution.Euphorbia trigona, native to Angola, Congo, Gabon and Malawi (Govaerts 2016) is widely commercialized as an ornamental, hedge plant and pot-plant across tropical subtropical and temperate regions.This species has the potential to escape from cultivation.In North America (Cuba and Belize) and India, where this species has become naturalized, it grows to form thickets in disturbed sites and abandoned gardens in dry and semiarid sites where it mostly spreads vegetatively by cuttings and stem fragments (see e.g.Balick & al. 2000; Oviedo & al. 2012; Govaerts 2016).In Europe, the taxon is reported only from Spain and in Canary Islands as present only in captivi-ty/cultivation (Ortiz 2016).The taxon is not reported yet to continental North African (APD 2022).Habitat in Tunisia.Euphorbia trigona occurs in the region of Monastir (CE Tunisia) within roadside in the shade of some cultivated Rosa sp.Notes.Euphorbia trigona can be confused to E. lactea Haw. which is also triangular, with similar pattern on the branches.However, this latter differs mainly by having more spreading and less winged branches.In addition, E. triangularis Desf.ex A. Berger is repeatedly mistaken for the similar-sounding name E. trigona.However, it differs mainly by showing spreading, 3-5-edged branches.Specimen visa (new records).TUNISIA: Monastir, 28.07.2021, ibidem, 25.10.2022, R. El Mokni s.n.(Herb.Univ.Monastir!).
Ma & Gilbert 2008)s a native range from Mexico to Bolivia and Trinidad.It was introduced as ornamental to Bangladesh, Benin, Cayman Is., China Southeast, Comoros, Dominican Republic, Hainan, India, Leeward Island, Puerto Rico, Taiwan, Windward Island and with no report in the Mediterranean area(POWO 2022a; APD  2022).It was also cultivated and escaped in Fujian, Hainan, Taiwan and widely cultivated in greenhouses of C and N China and throughout the tropics (see more inMa & Gilbert 2008).Habitat in Tunisia.Euphorbia cotinifolia subsp.cotinoides was found along roadside not far from planted ornamentals in the region of Tabarka, Jendouba (NW Tunisia).Notes.Euphorbia cotinifolia subsp.cotinoides differs from the typical subspecies most obviously by its ovate-rounded leaf blade; subtruncate at the base and obtuse in the apex (vs.orbiculate, apically rounded leaf blades in the subsp.cotinifolia) (see more in Ma & Gilbert 2008).Specimen visa (new records).TUNISIA: Jendouba, Tabarka, 15.10.2021,ibidem, 13.10.2022,R. El Mokni s.n.(Herb.Univ.Monastir!).Flora Mediterranea 33 -2023 Euphorbia cooperi N.E.Br. ex A. Berger, Sukk.Euph.83.1907 var.cooperi (Euphorbia subg.Euphorbia L. sect.Euphorbia L.)