This work is licensed under the Creative Commons Attribution 4.0 International License.
Introduction
The Tunisian Republic, a central-southern Mediterranean country with an area of 163,610 km2, and about 1,300 km of coastline including the African conjunction of the western and eastern parts of the Mediterranean Basin, is prone to plant invasions due mainly to its location on the crossroads within the Mediterranean. Such features, together with a high diversity of floristic communities from south to north and inter- and intra-continental movements of people, and the development of transport networks between the surrounding countries make the country a suitable place for an active settlement of many plant species outside their native areas. Thus, several alien species from all over the word were reported in the country as well established, mainly during the last two decades (see e.g. El Mokni & Iamonico, 2018a, 2018b, 2024; El Mokni & Domina, 2020; El Mokni et al., 2022, 2023, 2024; El Mokni, 2024). In the course of floristic surveys along coastal areas and saline wetlands, one more alien species (within the Boraginaceae s.l., genus Phacelia), not previously recorded for the vascular flora of the country is discovered, in 2024. The plant was found among roadside plant communities of cultivated fields in Menzel Ennour locality (Monastir, centraleastern Tunisia). Phacelia Juss. is a genus of approximately 200 species of annual and/or perennial herbaceous plants native to North and South America. The centre of diversity is in California where 93 taxa occur, of which 39 are endemic (Gilbert et al., 2005). Tunisian material was ascribed to one of these species that fits very well the descriptions of Phacelia tanacetifolia (subg. Phacelia sect. Ramosissimae (Rydb.) Waiden & R. Patt. (Walden & Patterson, 2012), a species, found native essentially in shrubland and woodland plant communities in California (Smither-Kopperl, 2018; Walden et al., 2023). The species is naturalized in Europe, Australia and New Zealand (see e.g., Essl & Rabitsch, 2002; Balogh et al., 2004; Lambdon et al., 2008; Medvecká et al., 2012; Pyšek et al., 2022; GBIF, 2024) and used as a cultivated catch crop around the world (GRIN, 2024). We here clarify its status of naturalization at the national level and confirm its casual occurrence to Algeria and Tunisia within the African continent. Description, and phenology together with its ecology in Tunisia are presented.
Material and methods
Since 2015, continuous botanical surveys have been carried out in various regions in central Tunisia to update the wild/alien flora. Data on the plant population and the habitat of the recorded taxon were also compiled. For the identification of the species, relevant literature (see e.g. Kirk, 2005; Kilian, 2016; Smither-Kopperl, 2018; Walden et al., 2023) and examination of specimens preserved at some accessible herbaria were used (CLF, LY, LYJB, MPU, NCY, P, REN, SLA and STR acronyms follow Thiers 2024 [continuously update])). Collected specimens were deposited at the personal herbarium of one of the authors (Herb. Ri. El Mokni) housed in the Herbarium of Monastir University (not listed in Index Herbariorum). Nomenclature of reported taxa is according to APD (2024) and the online Euro+Med PlantBase (Euro+Med, 2006 continuously updated). Family follows APG IV (2016).
Results and discussion
Taxonomic treatment
Phacelia tanacetifolia Benth., Trans. Linn. Soc. London 17: 280 (1835)
= P. tanacetifolia var. cinerea Brand, Botany 4:216. 1912; P. tanacetifolia var. pseudodistans Brand, H.G.A. Engler (ed.), Das Pflanzenreich IV, Vol. 251 (Heft 59), Verlag von Wilhelm Engelmann, Leipzig. 1913; P. tanacetifolia subvar. tenuisecta Brand, H.G.A.Engler (ed.), Pflanzenr., IV, 251: 91 (1913).
Lectotype. designated by Cecchi and Selvi, 2013 [2014]: USA, California, 1833, D. Douglas s.n. hololectotype: K000857695! (wild collected material on right, excluding left plant of K000857694! P. tanacetifolia grown in garden of Bentham at Kew) [Kew Catalogue, JStor]; isolectotypes: E 00288426 (wild-collected material on right, excluding two plants on left grown in garden of Bentham at Kew) [RGBE, JStor], G-DC-00134391 (wild-collected material on left, excluding plant on the right P. distans sensu lato) [ville.ge], CGE064606!; paralectotypes: E00288426 (two plants on left grown in garden of Bentham at Kew, excluding wild-collected material on right), K000857694! (P. tanacetifolia grown in garden of Bentham at Kew on left, excluding wild-collected material K000857695! on right).
Figure 1:
Phacelia tanacetifolia in Tunisia. Habitus and habitat on roadsides. Photograph by Ra. El Mokni (26. March 2024).
Slika 1:Phacelia tanacetifolia v Tuniziji. Habitus in rastišče ob cestah. Avtor fotografije Ra. El Mokni (26. 3. 2024).
Figure 2:
Phacelia tanacetifolia in Tunisia. A) opened flowers with pinkish blue to lilac bell-shaped corollas; B) alternate fernlike, deeply cut leaves. Photographs by A-A. El Mokni (26. March 2024).
Slika 2:Phacelia tanacetifolia v Tuniziji. A) odprti cvetovi z rožnato modrimi do lilastimi zvončičastimi venci; B) spiralasto nameščeni, praprotim podobni, globoko razdeljenimi listi. Avtor fotografij A-A. El Mokni (26. 3. 2024).
Figure 3:
Phacelia tanacetifolia in Tunisia. A-C) clustered flowers in typical helicoid cyme and scorpioid inflorescences types; D) details of fruits (capsules) with persistent corollas. Photographs by Ri. El Mokni.
Slika 3:Phacelia tanacetifolia v Tuniziji. A-C) grozdasti cvetovi v tipičnih helikoidnih in skorpijoidnih socvetjih; D) podrobnosti plodov (kapsul) z obstojnimi venčki. Fotografije Ri. El Mokni.
Description.Phacelia tanacetifolia is a fast-growing annual rough-hairy plant with branches in the upper part with upright or sloping stems, minutely glandular, that reach a height of about 70(−100) cm (Figure 1). The deeply cut leaves (fernlike) are alternate (Figure 2B). The flowers are quintuple, bell-shaped, and violet-blue in colour (due to the abundance of facelianin, Mori et al., 2006), clustered in inflorescences of scorpioid types (cf. Buys & Hilger, 2003; Figure 3). The flowers show a discoid nectary located on the flower base that is protected by throat scales. The calyx lobes are about 4–6( 7) mm, 6–8 mm in fruit, ± linear, densely long-hairy. The corolla ± persistent in fruit (Figure 3D), consists of five fused petals that are pale pinkish blue to lilac, in shades of blue and lavender or violet (Figures 2A, 3A, B & C) and 6–10 mm long. The stamens in number of five born on the corolla tube and project beyond the end of the corolla, 9–15 mm long, glabrous with purple filaments and violet anthers (Figures 2A, 3A, B & C). The style 11–15 mm, cleft 2/3–3/4, glabrous, deeply divided into two and also projects beyond the corolla when mature (Figures 2A, 3A, C & D). The fruit (capsule, Figure 3D) 3–4 mm, ± ovoid, glabrous proximally, puberulent to short-hairy distally. The seeds 1 or 2, 2–3 mm, wrinkled, pitted (Walden et al., 2023).
Flowering period. The natural flowering period is from March to May in its native distribution (California: southern Nevada, Arizona; Walden et al., 2023), but when planted as a crop it can be found in flower from April to December (northern hemisphere) or October to June (southern hemisphere), according to time of sowing. Under dry conditions in the Mediterranean, it flowers only from April to July (Kirk, 2005).
Phenology in Tunisia. According to our observations, Phacelia tanacetifolia (Figures 1, 2, 3) begins to vegetate in (end of January-) February, flowers in March, and fruits at the beginning of April.
Distribution. The species grows naturally on sandy or gravelly open plains and slopes in southwestern North America (including California, Nevada, Arizona and Mexico) but it was introduced to Europe in the early nineteenth century and other countries worldwide (e.g. Smither-Kopperl, 2018). It is now planted widely in many temperate regions, particularly Europe and Australia (see e.g. Tutin, 1992; Kirk, 2005; Farkas & Zajàcz, 2007). On the African continent, the plant was reported only as ‘cultivated’ in the Canary-Islands, as ‘introduced’/‘introduced: uncertain degree of naturalization’ in Morocco with no clear status of naturalization or as adventitious/casual, and for Algeria as casual alien (see e.g. Raab-Straube, 2017+; Meddour et al., 2020; APD, 2024; GBIF, 2024; POWO, 2024). On the online platform iNaturalist 2024 (https://www.inaturalist.org/), reports of Phacelia tanacetifolia were mentioned from South Africa in two locations, 1) South Africa, State Presedent C R Swart, Brenton-on-Sea, 6571, -34.06628, 23.02099, 1 Mai 2021, iNaturalist-observation: https://www.inaturalist.org/observations/77632765; 2) South Africa, Red Route, Greater Hermanus, WC, ZA, -34.36879, 19.24898, 6 oct. 2023, iNaturalist-observation: https://www.inaturalist.org/observations/186411962.
Occurrence in Tunisia and status of naturalization. We found only one small population (about 25 plants including few seedlings) of Phacelia tanacetifolia in one Tunisian locality (CE, Monastir, Menzel Ennour region) within an area of approximately one ha. So far, the original vector for the introduction of P. tanacetifolia in Tunisia is still unknown. However, the observation of this plant on the edge of cultivated fields raises the possibility of its accidental introduction due to contaminated annual crop seeds, without excluding other pathways of introduction as an accidental escapee from pots of ornamental plants. According to Pyšek et al. (2004) and Richardson & Pyšek (2006), we assess here P. tanacetifolia as a casual alien for Tunisia.
Habitat and ecology in Tunisia.Phacelia tanacetifolia has been observed in an anthropogenic site (roadsides and borders of plantations and cultivated lands) growing mainly with Ammi majus L., Anagallis arvensis L., Avena sterilis L., Chenopodiastrum murale (L.) S. Fuentes, Uotila & Borsch, Centaurea sicula L. subsp. sicula, Convolvulus althaeoides L. subsp. althaeoides, Emex spinosa (L.) Campd., Galactites tomentosus Moench, Glebionis segetum (L.) Fourr., Hordeum murinum L., Launaea sp., Lupinus pilosus L., Malva parviflora L., Medicago intertexta subsp. ciliaris (L.) Ponert, Medicago polymorpha L., Melilotus sulcatus Desf., Ononis reclinata L., Phalaris canariensis L., Plantago afra L., P. lagopus L., P. lanceolata L., Pseudopodospermum undulatum (Vahl) Zaika, Sukhor. & N.Kilian, Scorpiurus muricatus L., Scorzonera laciniata L., Sinapis arvensis L., Sonchus oleraceus L., etc.
Material studied (our collections). TUNISIA. Monastir: Menzel Ennour, on borders of cultivated lands and roadsides, 35°39′22″N, 010°46′15″E (coordinate system, WGS84), 27–30 m a.s.l., 26. March 2024, El Mokni s.n. (Herb. Univ. Monastir), ibidem, 3. April 2024, El Mokni s.n. (Herb. Univ. Monastir).
Notes. Phacelia tanacetifolia shows very close features to Phacelia distans Benth. with which it can be sometimes confused. The latter differs from P. tanacetifolia mainly by its short calyx lobes, 3–4 mm long in flower and 4–5 mm long in fruit, its short style, 7–12 mm long, and its richest capsules with 2–4 seeds [vs. calyx lobes 4–6(–7) mm long in flower, 6–8 mm long in fruit, style 11–15 mm long, and capsules with only 1 or 2 seeds] (cf. Horner, 1977).
Conclusion
We report a new casual alien plant species, Phacelia tanacetifolia, for the vascular flora of Tunisia, the third report to North Africa and the fourth record to the whole African continent. According to this record, also the genus Phacelia (Hydrophyllaceae included in Boraginaceae) is now new for the flora of Tunisia. Early detection of introduced species allows decisions to be made to prevent the species from spreading and becoming invasive, if not properly managed. It is important to take measures to eradicate this species in its actual habitats before its establishment. More field prospections should be planned in the nearer future to see whether the species continues to spread and, above all, whether there are further populations in Tunisia (and then – later – measures for control should also be considered). Otherwise, P. tanacetifolia can be maintained, under supervision, specifically as a forage source for bees. The plant is listed among the top 20 pollen producing flowers for honeybees and is highly attractive to pollinator insects including bumblebees (cf. Hayden, 2014). It is well known to produce a high density of flowers over a long time (Bloom season varies with location: Almost two months in the Mediterranean climate and can be extended more in several temperate regions (see e.g., Kilian, 2016)), particularly if there are successive monthly sowings, and is distinguished by providing a rich source of nectar and pollen.
Profilo Orcid
