Euphorbia hypericifolia L., Sp. Pl. 1: 454. 1753.

≡ Chamaesyce hypericifolia (L.) Millsp. In Publ. Field Columb. Mus., Bot. Ser. 2: 302 (1909) ≡ Anisophyllum hypericifolium (L.) Haw. In Syn. Pl. Succ.: 161 (1812).

Lectotype (designated by Fosberg & Mazzeo 1965: 191): Herb. Linn. No 630.4 (LINN) (image available at http://linnean-online.org/4598/ ).

Based on the terminology of El Hadidi (1973), Chen & Wu (2004), Li et al. (2008), Pahlevani & Riina (2011), Levin & Gillespie (2016), Sciandrello et al. (2016), Mahklouf (2023), and the morphological features observed on the collected specimens, the morphological description of Euphorbia hypericifolia, which is distinct from other Euphorbia species found in Morocco, is reported in the following section.

Botanical description. Herbs, annual, 15-100 cm high, glabrous, with taproot, stems more or less erect, generally much-branched from upper parts, branches deflexed at apex. Leaves 20-35 × (8)10-15 mm, simple, opposite, distichous, petiole 1-2.5(3) mm, blade elliptical-oblong to oblong-oblanceolate, glabrous, base asymmetric, oblique, apex obtuse or broadly acute, margins serrate or serrulate (or obscurely toothed) toward apex. Stipules triangular or deltate, 1.3-1.5 × 1.4-2 mm. Inflorescences formed of cyathia in dense globose cymes, axillary and terminal, with a peduncle 5-(18)20 mm long; involucre cup-shaped, glabrous, outside; glands 4, orbicular white or light pink, each involucre containing one female flower slightly exserted, surrounded by numerous male flowers subsessile. Ovary green, reddish brown when mature, glabrous, trilobed, with a long pedicel 0.5-1 mm long; styles free 3, each 2-fid (stigma) ± 1/2 length. Fruit a 3-lobed capsule, 1-1.5 × 2 mm, subglobose, smooth, glabrous, with one seed per lobe. Seeds brownish, 0.8-1.1 × 0.5 mm, 4-gonous, faces slightly wrinkled, caruncle absent.

Phenology. Based on our field observation, Euphorbia hypericifolia may be harvested at any time of year, although it flowers from the beginning of July to September and fruits from the end of September to December.

Chromosome number. Euphorbia hypericifolia is a diploid species with 2n = 32 (Wang et al., 1999; Sulaiman et al., 2020).

Specimens examined. Morocco. Rabat: vicinity close to the Prince Moulay Abdellah sports Field, on side of the N1 highway, 33° 57′ 55.1″ N, 6° 53′ 37.1″ W, 100 m, 10.IX.2021, L. Zidane & H. Khamar (RAB114579, RAB114580, RAB114582, RAB114583, RAB114584, RAB114585) (Fig. 3); Kénitra: along the national road N1, 34° 15′ 38″ N 6° 34′ 11″ W, 20-25 m, 24.IX.2021, H. Khamar (RAB114581).

General distribution. Euphorbia hypericifolia is native to the tropical and subtropical regions of the New World (that is, the southern United States, the Caribbean, and throughout South America) (Steinmann et al., 2016; Atha et al., 2018; POWO, 2023). It has been recorded as a weedy or invasive plant in many areas of the Old World, including the Mediterranean Basin, Western Europe (Belgium), tropical Africa, the Mascarene Islands, and certain parts of Asia (China, India, Iraq, Oman, Pakistan, Taiwan) (Coode et al., 1982; Li et al., 2008; CABI, 2023) (Fig. 4). The geographic distribution of this species in tropical Africa is still uncertain due to frequent confusion with Euphorbia indica Lam., a tropical plant that can be found in various regions of Africa and Asia (Emongor, 2008; Sciandrello et al., 2016).

Euphorbia hypericifolia has been reported as an introduced or rarely naturalized xenophyte in some Mediterranean countries, and its sporadic range is gradually expanding in this part of the world (Sciandrello et al., 2016). Thus, it has been recorded from Egypt (El Hadidi, 1973; Greuter et al., 1986), from Israel/Palestine (Greuter et al., 1986), from Crete (Gregor & Meierott, 2013), from Greece (Raab-Straube & Raus, 2015), from Italy (Sciandrello et al., 2016), from the Maltese Islands (Mifsud, 2018) and, in the western part of the Mediterranean Basin, it has been recorded from the Canary Islands (Otto & Verloove, 2016), from peninsular Spain (Verloove, 2005, 2015) and recently from Libya (Mahklouf, 2023).

Throughout its global distribution, E. hypericifolia has demonstrated its ability to occur in diverse habitats. It is commonly observed at elevations ranging from sea level to 600 m a. s. l., in humus-rich soils, wastelands, stony riverbanks, along roadsides, along the margins of ponds and marshes, and close to cultivated areas (Chen & Wu, 2004; Sciandrello et al., 2016; Mifsud, 2018). This plant is occasionally cultivated and commercially traded as an ornamental species (CABI, 2023).

Distribution and ecology in Morocco. So far, this species is known from the Moroccan North Atlantic phytogeographical region (Man-3 on the map in Fig. 1). In this geographical area, E. hypericifolia grows around Rabat and in some places in Kénitra. The bioclimate of this phytogeographical zone is between subhumid and semi-arid Mediterranean. Winters are temperate, the average annual rainfall is around 400 mm, and the average annual minimum and maximum temperatures are 12°C and 24°C, respectively. The relative humidity ranges from 81% in January to 70% in June (Climate-Data, 2023).

In the Rabat region, E. hypericifolia grows along the N1 highway near the Prince Moulay Abdellah Sports Center, where a population of about 250 individuals has been confirmed growing on clayey-sandy, more or less humid soil at an altitude of about 100 m; at this site, the following plants were found in association with it: Mercurialis annua L., Euphorbia peplus L., E. lathyris L., E. paniculata Desf., E. terracina L., E. hirta L., E. maculata L., Verbascum sinuatum L., Lupinus atlanticus Gladst., Lotus arenarius Brot., Ononis laxiflora Desf., Erigeron canadensis L., Plantago major L., Oxalis pes-caprae L., Emex spinosa L., Parietaria mauritanica Durieu, Urtica urens L., Physalis philadelphica Lam., Salpichroa origanifolia (Lam.) Baillon, Phyllanthus tenellus Roxb., Cyperus rotundus L., Bidens pilosa L., Erigeron sumatrensis Retz., Erigeron bonariensis L., Ambrosia artemisiifolia L., Pennisetum alopecuroides Steud., and low grasses.

However, in the Kénitra localities, mature plants of our new record were found in two humid places at altitudes ranging from sea level to about 20 m a. s. l., on limestone and sandstone substrates, in association with the following species: Ononis diffusa Ten., Astragalus baeticus L., Erigeron sumatrensis Retz., Silybum marianum (L.) Gaertn., Ricinus communis L., Urtica urens L., Verbesina encelioides (Cav.) Benth. & Hook. f. ex A. Gray, and Euphorbia helioscopia L.

The precise introduction pathway of E. hypericifolia to Morocco is unknown. However, previous findings have substantiated the existence of this species in various places beyond its indigenous habitats, likely attributable to human activities (Chen & Wu, 2004; Sciandrello et al., 2016). In the local context, the ruderal sites from which this species was collected have been used as parking and turning areas for long-distance trucks and various modes of transportation. The absence of morphological features such as hooks, sticky substances, or wings in the seeds of E. hypericifolia limits its ability to disperse over long distances. Consequently, it is widely believed that the unintentional introduction and subsequent naturalization of this species can be attributed to global trade (Mifsud, 2018). Similarly, this mode of dispersal has been attributed to other species within the same genus in certain countries, such as E. hirta L. in Morocco (Khamar et al., 2021), E. hypericifolia L. in Malta (Mifsud, 2018), E. glyptosperma Engelm. and E. serpens Kunth in Bulgaria (Petrova, 2018) and Romania (Sîrbu & Şușnia, 2018), E. davidii Subils in Switzerland (Hoffer-Massard, 2011) and Bulgaria (Vladimirov & Petrova, 2009), and E. prostrata Aiton in Hungary (Bátori et al., 2012).

The monitoring conducted over the past three years in Morocco has revealed that E. hypericifolia has a low level of invasiveness and demonstrates a propensity for easy spread within its local habitat. However, it lacks the capability to expand beyond its current distribution range. The findings presented align with the observations reported by Mifsud (2018) regarding the occurrence of this species on the Maltese Islands.