New records of cacti (Opuntioideae, Cactaceae) for the non-native flora of Tunisia and North Africa with a key to the Cylindropuntieae tribe

Botanical surveys undertaken in Central and Northern Tunisia (North Africa), mostly between 2015 and 2020, have revealed three new allochthonous cacti. The reported taxa belong to the genus Cylindropuntia (Cactaceae, subfamily Opuntioideae, tribe Cylindropuntieae). C. leptocaulis, C. prolifera and C. spinosior are here reported for the first time from North Africa. Updated nomenclature, descriptions, general and national distributions are pointed out for each species. An analytical key and field photographs are also provided.

These three newly reported taxa are: Cylindropuntia leptocaulis (DC.) F.M. Knuth, C. prolifera (Engelm.) F.M. Knuth and C. spinosior (Engelm.) F.M. Knuth. The new North African populations are described and the distribution and habitat of the species are outlined. An analytical key to the species of Cylindropuntia occurring in the wild in Tunisia with original photographs for each taxon are also provided.

Materials and Methods
Botanical surveys were carried out in Central and Northern Tunisia (North Africa), between 2015 and 2020. All records here reported are documented with descriptions and field photographs of each of these species. Their actual status (casual, sub-naturalised, naturalised, and/or potentially locally invasive) was pointed out and commented upon. The identification of all species was based on Pinkava (2003), Hunt et al. (2006) and Walters et al. (2011).
The paper enumerates new taxa in alphabetical sequence. Nomenclature of the species presented is in accordance with recent databases such as APD (2020) and Korotkova & Raab-Straube (2017+).
The species occurs in dry grassland and desert in a range from the west (Sonoran Desert) to the east (Chihuahuan Desert), also from Arizona and New Mexico (USA) to Sonora and Chihuahua (Mexico) (Pinkava, 2003;Hunt, 2006). Hybrids are formed in the overlapping areas, particularly with C. imbricata (Pinkava, 2003). It is sometimes cultivated in South Africa, and has now been found to be naturalised near Hopetown and Pofadder (Northern Cape Province) and east of Beaufort West (Western Cape Province) (Walters et al., 2011). In Europe, it is known in Spain (Sanz Elorza et al., 2004;Guillot Ortiz et al., 2009;Aymerich, 2015;Aymerich & Sáez, 2019), in France (Tison et al., 2014) and in Italy (Guiggi, 2010). The species is here reported  Figure 3. Cylindropuntia spinosior. A, B: Fruits, yellow and tinged reddish, broadly cylindric, fleshy, strongly tuberculate, spineless; C, D: Habit on a sun-exposed clayey slope. All photographs were taken by R.
Analytical key to species belonging to the genus Cylindropuntia occurring in the wild in Tunisia (including C. imbricata). for the first time in the flora of Tunisia and North Africa (Korotkova & Raab-Straube, 2017+;APD, 2020). In Tunisia, Cylindropuntia spinosior can be classified as naturalised to potentially locally invasive as it appears in only one extended population but with many colonies of very branched individuals (more than 25 within an area of about 2-3 ha). However, like other species from this genus, it certainly has the potential to become a national invasive alien if disseminated elsewhere by the activities of man and livestock.