New records of Asteraceae for the non-native flora of Tunisia and north Africa with some nomenclatural remarks

. Sixteen new Asteraceae are added to the non-indigenous flora of Tunisia. Six of them ( Dimorphotheca ecklonis , Gaillardia pulchella , Gazania linearis var. linearis , Guizotia abyssinica , Rudbeckia triloba and Tithonia diversifolia ) are also new for the flora of North Africa. Chrysanthemum morifolium is here first reported for the Mediterranean Basin. Seven genera ( Argyranthemum , Bidens , Dimorphotheca , Gaillardia , Guizotia , Rudbeckia and Tithonia ) are recorded for the first time for the vascular flora of Tunisia. Most of these species escaped from gardens and pots and became casual along roadsides and/or disturbed areas after cypsela dispersion (except for Chrysanthemum morifolium ). Some species, even though appearing to be well established locally and are potentially invasive at a worldwide level, still do not behave so in Tunisia. In addition to the floristic notes, the typification of the names Dimorphotheca ecklonis , Gorteria linearis and Mirasolia diversifolia are discussed.


Introduction
The northern African flora is very rich and highly diverse due to the presence of Mediterranean, Saharan, and Macaronesian floristic elements (White, 1983). Before human settlement, the landscape was mainly dominated by evergreen deciduous and coniferous forests. The most fertile lowlands have been used for agriculture since Roman times and the plant climax communities are nowdays confined to restricted patches. Agriculture along with the non-controlled importation of seeds and the introduction of ornamental plants have favored over time the installation of many non-native plants (El Mokni pers. obs.; see e.g., El Mokni et al., 2012;El Mokni, 2020a).

Distribution and habitat.
Argyranthemum frutescens (Anthemideae Cass.), known as Paris daisy, marguerite or marguerite daisy, is a sub-shrub (about 61-91 cm high) known for its very fragrant flowers. It is native to the Canary Islands, Spain (Humphries, 1976a). It is also widely cultivated as an ornamental in private gardens and public parks in many countries. The species is catalogued as a weed by Randall (2003). In Europe, the plant is cultivated in Portugal, France, and Sicily, and it is a casual alien in Italy, Sardinia and Corse (Greuter, 2006+;Galasso et al., 2018). It is also cited as naturalized alien in New Zealand (Webb, 1987) and in southern California (Calflora, 2021). In North Africa, the plant was known so far as cultivated in Lybia and Morocco (Greuter, 2006+;Dobignard & Chatelain, 2011). It is here recorded for the first time in Tunisia, where it grows on palm trees of Bizerta ( Figure 1A-B) and in some irrigated public gardens, sidewalks, and disturbed areas near wetlands in the Monastir region.
Distribution and habitat. Artemisia absinthium (Anthemideae Cass.) is a perennial herb, growing up to 70(-150) cm tall and developing abundantly branching shoots. It is native to Eurasia and some areas of North Africa. Nowadays, the plant is more widespread and occurs in other continents, mostly due to cultivation (Maw et al., 1985;Gams, 1987). In Tunisia, this taxon was formerly planted and has become locally common through the lowlands.
Taxonomic notes. Artemisia absinthium is morphologically similar to A. arborescens L. from which it differs by the unpunctuated leaves (vs. more or less punctate), the petiolate with auriculate petiole (vs. non-auriculate), and the labrous corolla with glandular cypselae (vs. not glandular) (Quézel & Santa, 1963

Distribution and habitat.
Bidens pilosa (Coreopsideae (Less.) Lindl.) is an erect annual herb, 20-100(-150) cm tall with quadrangular stems, opposite leaves, the upper ones being trifoliolate or imparipinnate with 2-3 pairs of pinnae and a single terminal leaflet. It is native to tropical America but is now a pantropical weed (Wagner et al., 1999). It is becoming an important weed in crops, pastures, wastelands, gardens, cultivated areas, and along roadsides (Galinato et al., 1999) in southern North America, South America, West and South Africa, East of Suez Canal, Europe, South-East Asia, North and South-East Australia, and some Pacific and Atlantic islands (GBIF, 2020). In North Africa, the species was known so far as naturalized alien in Egypt and Morocco, alien with unknown status in Lybia, and casual alien in Algeria (Greuter, 2006+;APD, 2020). It is here recorded for the first time in Tunisia, where it occurs as a casual weed along sidewalks of railways and roadsides ( Figure  1C-E) in Bir Bouregba (Cap-Bon region) and near a nursery of ornamental plants in Monastir region (CE Tunisia).
Taxonomic notes. In the Mediterranean area, Bidens pilosa is morphologically quite different from other Bidens taxa, mainly based on its leaf segments, indumentum, calycular bracts, and ray florets. The more similar species is B. frondosa L. from which it differs by characters of the cypselae. In B. pilosa cypselae are black or dark-brown, linear-fusiform (1.0-1.5 cm long, flat, 4-angled, sparsely hairy) with 2-3(-5) erect to divergent, retrorsely barbed awns 1-2 mm. In B. frondosa cypselae are blackish to brown, obcompressed, obovate to cuneate with 2 +/-erect, antrorsely or retrorsely barbed awns 2-5 mm), short spatulate calycular bracts, with white ray florets, ray florets at least 2-times longer than disc florets, longer stem, beneath of leaf usually dense pillosulose-tomentose indumentum (see Keil, 2012b Alavi, 1983: 195]: Habitat in Europae arvis, Herb. LINN no. 1035.4 (LINN!, image of the lectotype available at http://linnean-online. org/10874/). (Calenduleae Cass.), probably native to Asia and southern Europe, was brought to America by early settlers, and then cultivated in many gardens as a medicinal herb (Yoshikawa et al., 2001;Ukiya et al., 2006). It is an herbaceous perennial plant that reaches 80 cm tall, producing yellow or orange flowers about 4-5(-6) cm in diameter. In Europe, the plant is well naturalized in central Italy, Siciliy, Sardinia, and Spain, cited as casual alien in Portugal and Malta (Greuter, 2006+;Galasso et al., 2018). In France, it seems that the species is an occasional alien which persists only for a certain time where it has been cultivated as ornamental plant (Tison & de Foucault, 2014;Tison et al., 2014). The species is also widely naturalized in Europe (north to southern England) and elsewhere in warm temperate regions of the World. In North Africa, the plant was known so far as cultivated in Lybia and naturalized in Morocco (Greuter, 2006+;Dobignard & Chatelain, 2011). Calendula officinalis is here recorded for the first time in Tunisia, where it can be considered as casual alien found in some sewages in the centre ( Figure 1F-G) and in some irrigated public gardens, sidewalks in the centre and north of the country.    (Bremer & Humphries, 1993;Oberprieler et al., 2006). According to Kondo et al. (2003) polyploidy and hybridization are frequent in the genus making it taxonomically difficult. The genus is of considerable horticultural interest, with some 7.000 autumn-flowering plants named Ch. morifolium, an enormous hybrid complex developed in China over many centuries from multiple hybridizations involving several paternal species (including Ch. indicum L.) rather than only two or a few wild species, with an extinct species and its subsequent cultivars serving as the maternal parents (Galasso et al., 2020;Ma et al., 2020). It is well known for its commercial cultivars, which are globally important cut flowers and pot plants (Bhattacharya & Teixerra da Silva, 2006). Chrysanthemum morifolium is a subshrub native to eastern Asia. The wild prototype of this cultigen (Ma et al., 2020) introduced from China and now widely cultivated throughout the world is not yet recognized (Bailey, 1923). Autumn-flowering perennial Chrysanthemum plants were successfully introduced to France in 1789, and in 1792 the French botanist Ramatuelle proposed the name Matricharia morifolia (≡ Ch. morifolium) for one of these cultivars called "Old Purple" (Gosling, 1970). It is unknown when it was firstly introduced into the New World. It is related to Ch. zawadskii Herbich and Ch. arcticum L., which are widely cultivated as ornamental plants. Note that numerous cultivars were also created from Ch. morifolium (Heywood, 1976) but this species was not recorded neither in Europe nor in North Africa as alien (Greuter, 2006+;APD, 2020;GBIF, 2020).

Distribution and habitat. Calendula officinalis
Chrysanthemum morifolium occurs in Tunisia as casual in some sewages in Bizerta city (Figure 2A), in the margins of some public gardens, sidewalks in Sousse city and its surroundings and with abandoned populations on sidewalks in the centre of El Hamma and Zarzis cities. Distribution and habitat. Dimorphotheca Vaill. ex Moench (Calenduleae Cass.) includes about 20 species native to Zimbabwe, Angola, Namibia, and South Africa. Some Dimorphotheca species are naturalized in North America, Europe, and Australia (Strother, 2006b;Nordenstam, 2007;Pruski, 2015;Galasso et al., 2018). It includes the suffrutescent to shrubby species D. ecklonis, a popular garden plant native to South Africa but regarded as a weed in Mediterraneanclimate regions (Mediterranean basin, North America and Australia). In the Iberian Peninsula, D. ecklonis has been reported as naturalized in Galicia, Valencian Community, and Catalonia (González-Martínez, 2015;Aymerich, 2016;Sáez et al., 2016). In continental North Africa, D. ecklonis is here firstly reported (Greuter, 2006+;APD, 2020; GBIF, 2020) as casual ( Figure 2B) since it was recorded for many years from many sites in Tunisia in disturbed areas escaping from cultivated individuals in the surroundings.
Taxonomic notes. Dimorphotheca ecklonis is morphologically very similar to the closely related D. pluvialis (L.) Moench, D. fruticosa (L.) DC., D. sinuate DC., and D. jucunda E. Phillips. Compared to D. ecklonis (taxon that shows long ray florets, bright white on the upper side and light blue or violet on the lower side), D. jucunda differs in its typical reddish ray florets on both sides. With regard to D. sinuata and D. pluvialis (annual herbs with bisexual disk florets), D. ecklonis is a subshrubby plant with staminate disk florets. It shows linear-oblong to oblanceolate leaves and smooth ray cypselae up to 8 mm long, whereas D. fruticosa displays oblanceolate to obovate leaves and ray cypselae 5-7 mm long (Keil, 2012c).
Typification of the name Dimorphotheca ecklonis. Candolle (1838: 71) validly published the name D. ecklonis providing a diagnosis, the provenance ("in Africa Capensis"), and the collector ("legit cl. [clarissimo] Ecklon pl. exs. [planta exsiccata]"); moreover, "v.s." (= vidi sicco) was reported, so indicating that Candolle had seen at least one specimen. On the basis of Stafleu & Cowan (1976: 254) and HUH Index of botanists (2013a onwards), Ecklon's collection is preserved in many herbaria. We traced three specimens at G (barcode G-00460837), HAL (barcode HAL-0111581; image available at http://141.48.4.202/djatoka/jacq-viewer/viewer. html?rft_id=hal_0111581&identifiers=hal_0111581), and MO (barcode MO-357907) bearing plants collected by C. F. Ecklon. MO specimen (image available at http://legacy.tropicos.org/Image/57534) cannot be sure that it was collected before 1838 and part of the original material (Art. 9.4 of the ICN) since no date of collection is reported. Therefore, we prefer to exclude the specimen at MO for the lectotypification purpose. G specimens bear the following label: "N. 1823 | M. Ecklon 1835". These two annotations are clearly in different hand writing and only the first one "N. 1823" was written by Ecklon. On the other hand, HAL specimen bears the label "Dimorphotheca ecklonis DC. 85" and a recent and printed label including as date of collection "1829-1832". All things considered, also these two specimens (G and HAL) cannot be considered as original material with certainty. Since no original material appears to be in extant, we here proposed to neotypify the name D. ecklonis using the G specimen which is the more complete among those found, including various capitula and cypselae whose features are diagnostic in the genus Dimorphotheca (see e.g., Strother, 2006b;Pruski, 2015), we here designate it as the lectotype of the name D. ecklonis.  (Nesom, 2006). Nesom (2008) proposed a classification of Erigeron recognizing 35 sections. Erigeron karvinskianus is native to Mexico, Honduras, El Salvador, and Guatemala. It also occurs as alien in subtropical and temperate regions of all continents (see e.g., Greuter, 2006+;Nesom, 2008;Cullen, 2011;Nesom & Pruski, 2011;Hind, 2012;SANBI, 2012a). Until now, this species was not recorded in Tunisia (Greuter, 2006+;Le Floc'h et al., 2010;SANBI, 2012a;GBIF, 2020). It is here firstly reported from Aîn-Draham in the NW, where it occurs as a casual weed along sidewalks towards hotel 'Beau Séjour' ( Figure 2C).

Taxonomic notes.
Erigeron karvinskianus is the type of Erigeron sect. Karvinskia Nesom, a section including mostly perennial species with branched stems, spatulate to oblanceolate or linear leaves, long-pedunculate and erect capitula with white ray florets (becoming lavender at maturity), cypselae up to 1.9 mm long and 2-nerved, and pappus with 10-27 bristles (see Nesom, 1989Nesom, , 2008. The species more similar to E. karvinskianus is E. maxonii S.F.Blake, and it differs in having ray florets 0.1-0.3 mm wide [vs. (0.5-)0.8-1.3 mm wide ray florets], 3.3-4.5 mm long disc florets (vs. 2.3-3.3 mm long disc florets), and 1.5-1.9 mm long cypselae (vs. 1.0-1.4 mm long cypselae) (see Nesom & Pruski, 2011). (USDA-NRCS, 2020). It has been widely cultivated as ornamental and can be found cultivated and naturalized in Europe, South Africa, Central America, and on several islands of the Caribbean and the Pacific Ocean (GBIF, 2020; USDA-ARS, 2020). The plant grows on sandy or calcareous soils, often in grasslands, open disturbed areas, or cultivated places. It was also reported from coastal areas (dunes), human-made habitats (e.g., roadsides, gardens, and arable lands), river banks, and grassy places (Webb et al., 1988;Wagner et al., 1999;Strother, 2006c; Flora of Taiwan Editorial Committee, 2014). In North Africa, the plant is so far known only in the Canary Islands (Greuter, 2006+), therefore, it is here recorded for the first time as an alien species in continental North Africa.
Taxonomic notes. Gaillardia pulchella is morphologically very similar to G. aristata Pursh. Its annual habit and the variously colored ray florets (red or purple, sometimes with yellow tips, or multicolored) are reliable characters for separating it from G. aristata, which is a perennial species with wholly yellow or basally purple ray floret (Keil, 2012d
Taxonomic notes. Gaillardia ×grandiflor is a tetraploid hybrid resulting from a cross between the perennial G. aristata and the annual G. pulchella. The taxon arguably inherited its perennial habit from the former and its long flowering period and rapid growth rate from the latter (MBG, 2020). Many cultivars can be treated from seed, among which G. ×grandiflor 'Punch Bowl' (with bicolored ray florets; Figure 2D) and G. ×grandiflor 'Mesa Yellow' (with yellow ray and disc florets; Figure 2E) Key to species of Gaillardia found in Tunisia.  Figure 3).

Distribution and habitat. Gazania
Gaertn. is a genus well known for its horticultural uses, with several species and hybrids widely cultivated in gardens (see e.g., Magee et al., 2011). The genus belongs to the tribe Arctotideae Cass., subtribe Gorteriinae Benth. & Hook f., based on the connate and acute phyllaries, the ray florets 4-lobed, and the sclerified margins of the disc floret lobes (Karis, 2007). It comprises 18-20 species endemic to southern Africa (with the exception of the widespread G. krebsiana Less., extending to tropical East Africa) (Roessler, 1959;Magee et al., 2011). Gazania linearis (native to South Africa and Lesotho) has been cultivated as an ornamental plant since the 19 th century, becoming an invasive plant in several regions of the World (Hassler, 2019). In Europe, it is recorded in Italy (Galasso et al., 2018(Galasso et al., , 2019 and Spain (Laguna & Ferrer, 2013), whereas in North Africa, it was not yet reported. As a consequence, the Tunisian population is the first one for North Africa (APD, 2020; GBIF, 2020) as an alien in roadsides on sandy and loamy soils.

Typification of the name Gorteria linearis.
In continental North Africa, G. abyssinica was hitherto not known (Greuter, 2006+;APD, 2020;GBIF, 2020), so our finding represents the first report. In Tunisia, the species is found mainly as ruderal near areas drained by polluted water ( Figure 4A).

Distribution and habitat.
The genus Helianthus L. (Heliantheae Cass.) comprises 52 species, native to North America. Helianthus annuus (sunflower) was domesticated in North America at least 4000 years ago (Harter et al., 2004). It grows in disturbed areas (widespreading along roadsides and railroads), pastures, meadows, plains, and foothills. It is alien in central Argentina (Poverene et al., 2008) and Australia , where it is found in crop fields and uncultivated places (Poverene & Cantamutto, 2014) where is highly competitive with other species owing to its quick development (Geier et al., 1996). It is reported to be the most common and most problematic weed in sorghum crops in northern Tamaulipas, Mexico (Rosales-Robles et al., 2005). It was introduced in Europe as an ornamental plant at the end of the fifteenth century (Putt, 1997). Currently, H. annuus is used in Europe both as ornamental plant and as crop for production of seed oil. Alien populations grow in the continent in cultivated lands (and adjacent areas) as well as along roads. In North Africa, H. annuus is so far known in the Canary Islands (casual alien) and Morocco (naturalized), whereas in Lybia is reported as "in large-scale cultivation" (Greuter, 2006+). In Tunisia, the species was found in disturbed areas (sidewalks) of Bizerta city ( Figure 4B), along banks of the Béja region, and in croplands at Nefza. Taxonomic notes. According to Schilling (2006) (Urbatsch & Cox, 2006). Many species are cultivated as ornamentals outside their native distribution range. Six of these species have been introduced in Europe but only R. hirta L. and R. laciniata L. are considered to be widely naturalized in Europe (Greuter, 2006+). Rudbeckia triloba is native to the eastern North America (Britton & Brown, 1970), and it is considered as casual alien in few European countries (Greuter, 2006+) where it occupies human-made habitats, meadows, and uncultivated lands. Concerning North Africa, the species has been not yet recorded (see Greuter, 2006+;APD, 2020;GBIF, 2020). So, our observation is the first one for the whole north african area. We found it as casual alien in disturbed habitats.
Taxonomic notes. Rudbeckia triloba is morphologically close to R. hirta. based on stem (branched and up to 150 cm long in R. triloba vs. simple and up to 100 cm long in R. hirta), lower leaves (3-lobed vs. simple), capitula (many with a minute crown pappi vs. 1-3 without pappi) (see e.g., Maslo & Šarić, 2018: 9).   Neher, 1966;Everett, 1982;Gutiérrez & Stampacchio, 2015;Schiavinato et al., 2017). The greatest diversity of the genus is found in south-central Mexico. This genus comprises annual or perennial, strongly aromatic herbs or shrubs, with opposite or alternate leaves, usually pinnately dissected laminas, phyllaries fused in one series, and pappus of few scales or awns (Schiavinato & Bartoli, 2018). Many Tagetes species were introduced out of their native range as ornamental plants, or e.g. for medicinal uses (Singh et al., 2003). In particular, three annual species (T. erecta L., T. lunulate Ort. and T. tenuifolia Kunth) are commonly cultivated throughout the world as ornamental plants (Vasudevan et al., 1997). Tagetes erecta is currently known as alien from many European countries (see e.g., Greuter, 2006+;Galasso et al., 2018;GBIF, 2020) whereas in North Africa it is recorded in Morocco only (SANBI, 2012b). In Tunisia, T. erecta can be considered as casual alien growing along sidewalks and in disturbed areas ( Figure 4C-E).   et al., 2018). On the other hand the species is clearly introduced as ornamental and/or green manure in Africa, Asia, Oceania, West Indies, and Australia, where it is naturalized growing as a weed in roadsides, wastelands, crop fields, and homesteads (see e.g., Blake, 1921;Jex-Blake, 1957;GRIIS, 2018;ISSG, 2018;USDA-ARS, 2020). Tithonia diversifolia is able to form dense populations that impact negatively the cultivated lands. In fact, this species produces a large amount of small seeds, which can be dispersed by wind, water, and animals. Seeds may also be spread in dumped garden waste and through contaminated agricultural produce (Orwa et al., 2009). In addition, T. diversifolia produces allelochemicals which affect the nutrient uptake and growth of young native plants (Oyerinde et al., 2009). In North Africa, T. diversifolia has been still not recorded (see e.g., Greuter, 2006+;GBIF, 2019;APD, 2020) and the population found in Tunisia represents therefore the first observation. It is here considered as casual alien occupying disturbed areas ( Figure 5).

Taxonomic notes.
Tithonia diversifolia is similar to T. rotundifolia (Mill.) S.F.Blake and to Helianthus tuberosus L. Tithonia diversifolia has mostly alternate leaves with 3-7 acuminate lobes ( Figure 5A) with yellow ray florets (4-7 cm long) ( Figure 5B-D) and bright yellow disc florets (ligulae) ( Figure 5E-F). In contrast, T. rotundifolia has leaves with entire or with rounded lobes, and orange or reddish ray florets (2.0-3.5 cm long The first one is here selected as type". So, Blake designated the collection no. 2319 by E. Bourgeau as the type (lecto-) of the name. However, Bourgeau's collection consists of several specimens kept at different herbaria as he stated "SpeciMen exaMined", Blake (l.c.) stated: "Veracruz: ... Valley of Orizaba, May 12, 1866, Bourgeau 2319 (type collection: G, K, N)". So, he did not distinguish among the listed syntypes (G, K, and N specimens).