Euphorbia serpens Kunth, 1817

Mugnai, Michele, Lazzaro, Lorenzo, Nuzzo, Luca Di, Foggi, Bruno, Viciani, Daniele & Ferretti, Giulio, 2021, Synopsis of Euphorbia section Anisophyllum (Euphorbiaceae) in Italy, with an insight on variation of distribution over time in Tuscany, Phytotaxa 485 (1), pp. 1-65 : 40-41

16. Euphorbia serpens Kunth in Humboldt et al., Nov. Gen. Sp. 2(5): 52. 1817.

Type (lectotype, designated by Wheeler 1941: 198):— VENEZUELA. Cumana , s.d., Bonpland 407 ( P00669812 image!, isolectotypes P00118493 image!, F0056660 image!)

≡ Anisophyllum serpens (Kunth) Klotzsch & Garcke in Klotzsch (1860: 23)

≡ Chamaesyce serpens (Kunth) Small (1903: 709)

≡ Chamaesyce serpens (Kunth) Millspaugh in Parish (1913: 6), isonym

Description:—Herbs, annual, with slender taproot. Stems prostrate, mat-forming and rooting at nodes, 15–50 cm, glabrous. Leaves opposite; stipules connate, deltate, white to pink, membranaceous, 0.5–1.0(–1.2) mm, glabrous; petiole less than 1 mm, glabrous; blade ovate or orbiculate, 2–7(–9) × 2–6 mm, base asymmetric, rounded to subcordate, margins entire, apex rounded, usually retuse, surfaces glabrous; only midvein conspicuous. Cyathia solitary at distal nodes; peduncle 0.5–1.0(–2.5) mm. Involucre campanulate to turbinate, 0.3–0.7(–1.0) × 0.4–0.6 mm, glabrous; glands 4, yellow, oblong, 0.1 × 0.2 mm; appendages white to pinkish, forming narrow rim at edge of gland, 0.1–0.2 × 0.2–0.3 mm, margin entire or crenulate. Staminate flowers 5–10. Pistillate flowers: ovary glabrous; styles 0.2 mm, 2-fid ½ to nearly entire length. Capsules broadly ovoid or subglobose, 1.3–1.4 × 1.3–1.7 mm, glabrous; columella (0.9–)1.0– 1.2 mm. Seeds white to grey or pinkish, ovoid, slightly 3–4-angled in cross section, 0.7–1.1 × 0.4–0.7 mm, smooth.

Chromosome number:—2n = 22, 24 ( Hügin 1998a); n = 6, 8, 12 ( Hügin 1998a); n = 11 ( Khatoon & Ali 1993); 2n = 22 ( Benedì & Orell 1992b); n = 6, 8 ( Subils 1977); n = 12 ( Urbatsch et al. 1975).

Ecology:—Accidentally dispersed by humans and other animals, including livestock, as contaminant; globally considered as weed of cereals, orchards, plantations, vegetables, roadsides and pastures.

Taxonomic annotations:—The synonymy E. serpens var. montevidensis Casar. ex Boissier reported in Galasso et al. (2018a) is erroneous. In fact, the name E. serpens var. montevidensis (Boiss.) Cabrera (1953: 284) is validely published, but is a synonym of E. klotzschii Oudejans (1989: 46) . Euphorbia serpens has been confused with E. humifusa in many cases, because of their shared glabrescence. However, the two species significantly differentiate in leaves and stipules morphology. Notwithstanding the subspecies rank is not considered as valid by some authors (e.g. WCSP 2018, Steinmann 2014), other botanists (e.g. Verloove & Lambinon 2011, Wolf & Király 2014, Lazzeri et al. 2018) recognized two subspecies of E. serpens : E. serpens subsp. serpens and E. serpens subsp. fissistipula . Many authors (e.g. Jauzein 1989, Hügin 1998a, Wolf & Király 2014), together with different chromosome numbers, reported some morphological characters that allow indeed differentiating the two subspecies.

a. Euphorbia serpens subsp. serpens

= Euphorbia serpens var. radicans Engelm. ex Boiss. in Candolle (1862: 30). Type (lectotype, designated by Wheeler 1941: 199):— MEXICO. Tampico, s.d., Berlandier 140 (G, isolectotypes US 00095421 image!, P00716333 image!)

≡ Chamaesyce radicans (Engelm. ex Boiss.) Millspaugh (1916: 411)

Iconography:— Jercinovic (2007: Tab. 21, under the name Chamaesyce serpens ), Benedì (1997: Fig. 70, under the name Chamaesyce serpens ), Jauzein (1989: 14, fig. upper left), Fig. 28.

Alien status:—Neophyte native to the New World, it can be considered naturalized in Italy. The first record for Italy date back to 1998 for LIG ( Hügin 1998a). The first European occurrence is from 1842 for France and subsequently in Germany, Denmark, Belgium, United Kingdom, Spain, Portugal, Austria, Switzerland, Hungary, Italy, Greece, Cyprus, Bulgaria and Romania. It results as naturalized in many cases, especially in Mediterranean region ( Sîrbu & Șușnia 2018; see also Haddad 2016).

Occurrence in Italy:—Naturalized in LOM, LIG, EMR, TOS, MAR, SIC and SAR; casual in VDA ( Bovio 2019, Galasso et al. 2019) and TAA ( Galasso et al. 2018a).

b. Euphorbia serpens subsp. fissistipula (Thell.) Verloove & Lambinon , New J. Bot. 1(1): 39. 2011.

Type (lectotype, designated by Hügin 1998b: 223):— FRANCE. Güterbahnhof Montpellier [Montpellier freight yard], 6 July 1905, Thellung s.n. ( Z000017123 image!, isolectotype K000911897 image!)

≡ Euphorbia serpens var. fissistipula Thellung (1907: 755)

≡ Chamaesyce serpens (Kunth) Small subsp. fissistipula (Thell.) Hügin (1998b: 223)

Iconography:— Jauzein (1989: 14, fig. bottom left).

Alien status:—Neophyte native to the New World, it can be considered doubtfully occurring in Italy. The only one record for Italy is for LIG by Hügin (1998a, see Taxonomic annotations). In Europe it is recorded also for Denmark, Belgium and France ( Hügin 1999, Wolf & Király 2014, Sîrbu & Șușnia 2018).

Occurrence in Italy:—Recorded for LIG by Hügin (1998a). We consider its presence in Italy as dubious (see Taxonomic annotations).

Taxonomic annotations:—According to the herbarium material examined, and as justified by the different chromosome numbers ( Hügin 1998a), we consider the two subspecies taxa as valid. Most of European records refer to E. serpens subsp. serpens , while E. serpens subsp. fissistipula was recorded few times, in Denmark, Belgium, France and Italy ( Hügin 1999, Wolf & Király 2014, Sîrbu & Șușnia 2018). The presence of E. serpens subsp. fissistipula in Italy ( LIG) reported by Hügin (1999) is based on data on chromosome numbers and is not linked to any herbarium specimen. Moreover, we did not find any herbarium material confirming the presence of this subspecies in the past in Italy.All the material we examined from Italy corresponds to E. serpens subsp. serpens . Accordingly, at the moment we could verify only the presence E. serpens subsp. serpens present in Italy (including LIG), even if further investigations are required for an accurate distribution of these subspecies taxa in Europe.