First record of Diplotaxis kohlaanensis (Brassicaceae) for the eastern African flora with taxonomical and phytogeographical remarks

Biodiversity Data Journal 13: e161978 doi: 10.3897/BDJ.13.e161978 Taxonomy & Inventories First record of Diplotaxis kohlaanensis (Brassicaceae) for the eastern African flora with taxonomical and phytogeographical remarks Salvatore Cambria , Manuela Porrovecchio , Adriana Santanello , Pietro Minissale , Gian Pietro Giusso del Galdo ‡ Department of Biological, Geological and Environmental Science, University of Catania, Via A. Longo 19, I - 95125, Catania, Italy Corresponding author: Salvatore Cambria ([email protected]), Pietro Minissale ([email protected]) Academic editor: Gianniantonio Domina Received: 13 Jun 2025 | Accepted: 03 Aug 2025 | Published: 07 Oct 2025 Citation: Cambria S, Porrovecchio M, Santanello A, Minissale P, Giusso del Galdo GP (2025) First record of Diplotaxis kohlaanensis (Brassicaceae) for the eastern African flora with taxonomical and phytogeographical remarks. Biodiversity Data Journal 13: e161978. https://doi.org/10.3897/BDJ.13.e161978 Abstract Background Diplotaxis (Brassicaceae) is a genus widely distributed in the temperate areas of Europe, Asia and Africa, reaching its greatest diversity in NW Africa, Cape Verde and the Mediterranean area. In eastern Africa, this genus is only represented by D. harra (Forssk.) Boiss. in Somalia and Djibouti, while no native species of Diplotaxis have been recorded from Ethiopia. New information The finding of Diplotaxis kohlaanensis A.G. Mill. & J.A. Nyberg, originally described from northern Yemen, is here reported for the first time in the Simien Mountains. Our finding has a particular phytogeographical and ecological significance, highlighting the relevant floristic relationships of the Arabian Peninsula mountains with the Ethiopian highlands. In ‡ ‡ ‡ ‡ ‡ © Cambria S et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. addition, our investigations confirm the outstanding number of exclusive taxa shared by these two areas testifying to the past phytogeographical connection between these two territories. D. kohlaanensis is localised on the high-altitude cliffs, which represent a highly conservative environment for relict species. Finally, the taxonomical relationships of this taxon within the Diplotaxis harra complex are also examined. Keywords biogeography, chasmophilous vegetation, Ethiopia, morphology, taxonomy Introduction Diplotaxis DC., a genus of Brassicaceae Burn. (tribe Brassiceae DC.), is mainly distributed in the temperate areas of Europe, Asia and Africa, including 30-40 species (Martinez-Laborde 1988, Warwick and Hall 2009, Pignone and Martínez-Laborde 2010, Gómez-Campo 2011, POWO 2025) with the greatest diversity in NW Africa, Cape Verde and the Mediterranean area (Martín and Sánchez-Yélamo 2000, Rustan 2008). According to the Flora of Ethiopia and Eritrea (Edwards et al. 2000), the most recent academic flora dealing with these countries, no species belonging to this genus occurs in Ethiopia, while other sources (Oliver 1868, Pignone and Martínez-Laborde 2010, POWO 2025) report the presence of weedy species D. erucoides L. For the remaining eastern African countries, the only known native species of Diplotaxis is D. harra (Forssk.) Boiss., occurring in northern Somalia and Djibouti (Thulin 1993). This species, originally placed by Schulz (1919) in the section Catocarpum, shows rather uncertain relationships and a quite isolated position within the genus Diplotaxis (Pradhan et al. 1992, Warwick et al. 1992, Martín and Sánchez-Yélamo (2000). Besides, this taxon is morphologically very variable (Martínez-Laborde 1991) and widely distributed from the (sub-)desertic territories of North Africa eastwards to Afghanistan and Pakistan (Zohary 1966, PottierAlapetite 1979, Fennane 1999, POWO 2025). Two closely-allied taxa, D. crassifolia (Raf.) DC. and D. lagascana DC., sometimes treated at subspecific level, are also known from Sicily (Italy) and southern Spain, respectively (Castroviejo et al. 1993, Pignatti et al. 2019, Brullo and Brullo 2020). Besides, the perennial populations of D. harra from North Africa, alternatively referred by various authors (Maire 1965, Pottier-Alapetite 1979, Fennane 1999) to the subsp. crassifolia and lagascana, but clearly distinguished by the morphology of the leaves and siliques, are provisionally attributed to the variability of the species, although further taxonomic, ecological and chorological investigations are desirable. The D. harra complex includes all the endemic taxa recorded from Cape Verde (Rustan 2008), whose origin is quite recent (Quaternary) likely from the western Saharan populations of D. harra as proposed by Franzke et al. (2017). Regarding the southern boundaries of D. harra, it reaches the central-southern part of the Arabian Peninsula and, particularly, Saudi Arabia, Yemen and Oman (Miller and Cope 1996), where Miller and Nyberg (1994) found and described a new closely-related species named D. kohlaanensis from the mountain area of Kuhlan (northern Yemen). According to these authors, this taxon is morphologically and ecologically quite distinct from D. harra, 2Cambria S et al especially for its shrubby habit, corolla with longer petals and larger siliques. Whereas, relating to its ecology, it occurs on carbonatic or calcarenitic rocks located at high altitudes (2,300-3,000 m a.s.l.), featuring cool and humid environmental conditions where D. harra is typically found in the Arabian Peninsula. Recently, D. kohlaanensis was found by Brinkmann et al. (2009) also in the Jabal al Akhdar mountain range (Oman), although this record should be considered at least dubious as the ecological context seems unlikely for the species. However, other reports for Oman, such as those of the specimens in the GBIF database from the Dhofar Mountains, seem to demonstrate the presence of the species in that country. During field surveys on the Afromontane and Afroalpine vegetation of the Simien Mts. (north-western Ethiopia), a population of an unknown species belonging to the genus Diplotaxis was found on the vertical cliffs just below the peak of Mt. Inatye, at an altitude between 3,700 and 3,900 m a.s.l. Further field and herbarium investigations allowed us to attribute this plant to the aforementioned D. kohlaanensis due to the peculiar morphological features of the stems, leaves, flowers and siliques. Our finding is quite relevant since it represents the first record of a native species of the genus Diplotaxis in Ethiopia, thus contributing to update the already significant pool of species shared by the Ethiopian highlands and the mountains of the southern Arabian Peninsula. This relatively surprising discovery in a territory that is quite well known from a floristic point of view, at least in the higher areas (Puff and Nemomissa 2001, Puff and Nemomissa 2005), is probably related to the localisation of the species on vertical walls that are difficult to access and perhaps also to its flowering period in the dry season. A detailed morphological description of the plants belonging to the surveyed population, as well as the phenology, conservation, distribution and ecology of the species in Ethiopia is discussed in this paper. Furthermore, a taxonomic review of the currently recognised taxa within the D. harra species complex is presented with the elaboration of a key. Finally, the floristic relationships between the Simien Mountains and the mountain ranges of the southern Arabian Peninsula are analysed in detail, highlighting the vegetation types that host the greatest number of shared species between eastern Africa and south-western Asia. Materials and methods The study area is localised in the north-western part of Ethiopia and, in particular, in the Simien Mts. (13°140' N, 38°210' E) where the highest peak of Ethiopia is found (Mt. Ras Dejen, 4,540 m a.s.l.). This massif is the remnant of a major Oligo-Miocene shield volcano, deeply eroded by the Tekeze River and its tributaries, surrounding the massif (Kieffer et al. 2004). A peculiar feature is the presence of a steep slope of ca. 1,000 m connecting the high plateau to the lowlands. The areas exceeding 3,500 m of altitude are characterised by a mountain climate with frequent frost and occasional snow (Hurni 1988), with mean daily temperature ranging from 1.5°C in the coldest day up to 14.6°C in the hottest day (Hurni and Stähli 1982). Rainfalls chiefly occur during the wet season (May-August), followed by a dry season, First record of Diplotaxis kohlaanensis (Brassicaceae) for the eastern ... 3 with mean annual values of 1,515 mm at Gich Camp (Hurni and Stähli 1982). Moving from the northern to the southern slopes of the Simien Mts., rainfalls are typically decreasing. Our field surveys were performed in December 2024 and January 2025. Flowering and fruiting specimens of Diplotaxis kohlaanensis were collected on the vertical cliffs below Mt. Inatye (Fig. 1). As it is located in rather inaccessible stands, it was decided to collect a limited quantity of specimens by harvesting only the elements relevant for the proper identification of the plant, such as basal and cauline leaves, flowers and siliques, also for avoiding any potential damage to the population. The collected specimens are preserved at the Herbarium of Catania (CAT, herbarium acronym follows Thiers (2025)). The morphological investigations on the Ethiopian material belonging to D. kohlaanensis were carried out on five individuals. All the specimens were compared with data from the protologue (Miller and Nyberg 1994) and other relevant literature (Zohary 1966, PottierAlapetite 1979, Thulin 1993, Miller and Cope 1996, Pignatti et al. 2019, Brullo and Brullo 2020). Figure 1. Overall range of Diplotaxis kohlaanensis according to literature and herbarium data (green dots) and field surveys (purple dot) and distribution map of D. kohlaanensis in Ethiopia (red dot).  4Cambria S et al The comparison amongst the specimens belonging to D. harra, D. crassifolia, D. lagascana and D. kohlaanensis was carried out using both living material and dried specimens preserved in B, BR, CAT, E, K, LI, MA, PAL, SANT, SAV, US, W and WAG. In particular, the four species have been differentiated, based on the following characters: habitus, leaf and stem indumentum, leaf blade shape and size, leaf margins, corolla colour, petal size and silique size and shape (including beak length). In addition, the conservation status of D. kohlaanensis in Ethiopia was assessed by using the IUCN criteria (IUCN 2001) and the guidelines for regional application (IUCN 2003), according to the GeoCAT (Geospatial Conservation Assessment Tool) programme (Bachman et al. 2011). Finally, for the phytogeographic study, a checklist of the species occurring in the Afromontane and Afroalpine areas of the Simien Mts. exceeding 3,000 m a.s.l. was elaborated by using literature (Puff and Nemomissa 2005, Melese et al. 2018) and field surveys. Then, with the support of the POWO database, it was possible to identify species occurring in the Simien Mts. with a disjunct distribution range in eastern Africa and the Arabian Peninsula. Subsequently, for each species, the vegetation type was identified with the support of literature (Edwards and Hedberg 2009) and field data. Besides, the plant life form of these taxa has also been investigated. To compare the plant life forms of taxa with an East Africa and Arabian distribution, a stacked bar chart was generated using RStudio (RStudio Team 2020) and the tidyr and ggplot2 libraries (Wickham 2016, Wickham et al. 2017). Data resources The following herbarium specimens have been examined: Diplotaxis harra (Forssk.) Boiss.: YEMEN: Gov. Hadhramout, Jol Plateau, on the pipeline rd. from Wadi Araf to Tawila fields, immediately S of the highest point and watershed, 15°09'53.8"N, 49°22'37.1"E, 3 September 2001, 1620 m alt., N. Kilian, P. Hein & M. A. Hubaishan s.n. (MA917618; WAG1970184!); OMAN: Dhofar, Mughsayl, volcanic escarpments and foothills, 16.891781 N 53.823051 E, 28 September 2015, P. Escobar Garcia s.n. (W201602241!); Dhofar, Shaat, Rass Saijr Cliffs, forest and clearings, 16.763547 N 53.602058 E, 28 September 2015, P. Escobar Garcia s.n. (W201602242!); Dhofar, Taquah, Way to Wadi Darbat, deciduous forest, 17.070599 N 54.446298 E, 27 September 2015, P. Escobar Garcia s.n. (W201602243!); Dhofar, Al Mughsayl, Wadi in fondo alla discesa, dopo Al Mughsayl, lungo le pendici e il letto di sinistra. Alt. 50-100 m, 10 September 2002, M. Raffaelli, M. Tardeli, S. Mosti 851 (E00983905!); Dhofar, Wadi Mughsayl, alt. 0-250 m, 4 March 1994, I. McLeish 3437 (E00121242); Dhofar, road from Taqa to Medinat al Haq, in rough grass at the road side, 500 m alt., 17,073 N 54,255 E, 7 October 1984, R.A. Ash 185 (E00449433!); JORDAN: Elgi prope Petram, Wadi Musa, Arabia Petraea, 18 June 1909, F. Nàbělek 1403 (SAV0004618!); TUNISIA: Sousse, ca. 7 km on the road Knais to Gabghoub, off-road to artificial lake. Open terrain with herbs and shrubs, along lake, 90 m alt., 35°40.3' N, 10°26.3' E, 2 April 2003, J.J. Wieringa 4848 (BR0000025202021!); MOROCCO: Great Atlas, Gorges du Ziz between Rich and ErRachidia, surroundings of Tunnel du Leginaires, 21.1 km S Rich, 1280 m alt., 31°10' N, 04°23' W, 29 April 1993, R. Vogt 10366 & C. Oberprieler 4814 (B100354760!); SOMALIA: First record of Diplotaxis kohlaanensis (Brassicaceae) for the eastern ... 5 Togdheer, Burao District, Gaan Libaah (Gacan Libaax), ca. 140 km from Hargyesa on Hargyesa-Buran, fields, 2000 m alt., 28 December 1977, K. Elmi, M. Suliman 216 (WAG0338919!); Diplotaxis crassifolia (Rafin.) DC. : SICILY (ITALY): Sizilien: Bachschlucht hinter Porto Empedorle südwestl. Agrigento, rechte Talseite nahe dem Ausgang, 15 April 1965, 1620 m alt., H.E. Metlesics s.n. (LI253868!); Paternò sulle rupi calcaree oltre il Simeto, 1 May 1896, F. Tornabene s.n. (CAT3970!); Paternò, 15 Aprile 1894, P. Baccarini s.n. (CAT3971!); Pietraperzia, s.d., s.c. (PAL5624!); Torre di Gaffe, Licata (AG), 25 June 1991, G. Certa, F. Gendusa, E. Pira s.n. (PAL71359!); Diplotaxis lagascana DC.: SPAIN: Almería: Tabernas, Llanos del Duque, sobre substrato seco, pedregoso y salino, 20 March 1998, C.Morales, C.Quesada, L.Baena, J.E.Linares s.n. (SANT 40196!); Velez de Benaudalla (Espana, prov. Granada, Andalucia), alt. 50 m, campos de cultivo al lado de la carrettera, comunidade de terofitos, 17 March 1982, A.M. Negrillo, P. Aroza, J. Hurtado 12186 (BR000027543092V!); Velez de Benaudalla (Espagne, prov. Granada, Andalucia), El Azud de Vèlez, 40 m alt., bords des chemins, sur des sols remuès riches en petites pierres, 28 January 1980, M. Ladero, O. Socorro, J. Hurtado 10240 (BR000026282237!); Base de Sierra Grossa, Alicante, 11 November 1949, S. Rivas s.n. (US03584685!); Diplotaxis kohlaanensis A.G. Mill. & J.A. Nyberg: YEMEN: Amran to Kuhlan Road, limestone cliffs, 15 km E of Kuhlan, 2800 m alt., 26 March 1981, A.G. Miller & D.G. Long 3213 (E0038048! holotype; K001291634! isotype); on cliffs above the town of Kohlaan, 2700 m alt., 31 January 1979, J.R.I. Wood 2691, identified by A. G. Miller (E00449402!); on a cliffs above Kohlaan, 2300 m alt., 17 February 1973, J.R.I. Wood 2691, identified by A. G. Miller (E00449405!); on cliffs on the S West edge of Jebel Mahdad, 3000 m alt., 26 September 1978, J.R.I. Wood 2518, identified by A. G. Miller (E00449403!); Bait Al Alama, J. Al Mahdad, 20 km W of Amran, SW facing sandstone cliffs, 2900 m alt., 26 September 1978, A.G. Miller 236 (E00449404!); OMAN: Western Hajar Mountains, steep N-Exposed cliff in TeucrioJuniperetum, 16 April 2011, A. Patzelt s.n. (E00702050!); ETHIOPIA: Simien Mt., rocky cliffs near the path between Inatye Mountain and Chennek, 3900 m alt., 13°15'20.17"N, 38°10'9.31"E, 23 December 2024, S. Cambria s.n. (CAT!). Taxon treatment Diplotaxis kohlaanensis A.G. Miller & J.A. Nyberg 1994 Material a. scientificNameID: Diplotaxis kohlaeensis; kingdom: Plantae; order: Brassicales; family: Brassicaceae; genus: Diplotaxis; continent: Africa; country: Ethiopia; locality: Simien Mountains; verbatimElevation: 3900 m; verbatimLatitude: 13°15'20.17"N; verbatimLongitude: 2 38°10'9.31"E; individualCount: 100; identifiedBy: S. Cambria; dateIdentified: 23-12-2024; occurrenceID: 0DD55C97-CA41-5778-B3F7F8CECAA94124 6Cambria S et al Description Shrubby and compact chamaephyte, generally glabrous, with many stems arising from a woody rootstock. Flowering branches erect or ascending, 30–60 cm long. Leaves slightly fleshy, glaucous, all petiolate with a well-marked whitish mid-rib. The lower ones with ovate to oblong-ovate blade, 15–80 × 10–20 cm, obtuse apex and serrate margin with 4–6 pairs of teeth or sinuate to entire, rarely with few scattered hairs. Upper leaves smaller, 5–40 × 5–10 mm, provided with a shorter petiole. Racemose inflorescence, erect or ascending, with the flowers overtopping the buds. Flower pedicels 10–14 mm long, equal or shorter than to the petals. Calyx with four sepals, 5–6 mm long, generally 2.5–3 times shorter than the petals, externally hairy particularly along the mid-rib and near the base. Inner sepals 1.8-2.5 mm broad and saccate at base, the outer 1.5–2 mm broad, with non-saccate base and clearly hooded tip. Corolla with four petals, pale yellow, broadly obovate and narrowing below into a linear claw, 10–14 × 5-6 mm, with rounded tip. Androecium consisting of 6 stamens; the median 8–11 mm long, with prominent nectarial glands at the base; the lateral 6–7 mm; anthers 2–3 mm long. Gynoecium with cylindrical ovary, glabrous, shortly stipitate; stigma bilobed. Siliques erect or patent, linear to linear-oblong, flattened, 12–40 × 2.5–3.2 mm, with the seeds in two rows; beak seedless, 1.5–2 mm long; Seeds pale reddish to brown, flattened, 1–1.5 × 0.5–l mm (Fig. 2, Fig. 3). Figure 2. Diplotaxis kohlaanensis in the Ethiopian stands: A Natural habitat where an individual is highlighted by a red circle; B Chasmophilous vegetation with Aeonium leucoblepharum and D. kohlaanensis; C Habitus of D. kohlaanensis; D Detail of the leaves and flowers.  First record of Diplotaxis kohlaanensis (Brassicaceae) for the eastern ... 7 Distribution Based on the current knowledge, the species is localised in Ethiopia on the vertical, basaltic, north-facing cliffs of the Simien Mts. at an altitude ranging from 3,700 to 3,900 m a.s.l. Ecology The species was found on the escarpment below Mt. Inatye, which is characterised by chasmophytic vegetation rich in rare and phytogeographically relevant species, such as Aeonium leucoblepharum Webb ex A.Rich., Arabis alpina L. subsp. alpina, Campanula edulis Forssk , Poa simensis Hochst. ex A.Rich., Helichrysum citrispinum Delile var. citrispinum, Dianthus longiglumis Delile, Rosularia semiensis (J.Gay ex A.Rich.) H.Ohba, Asplenium aethiopicum (Burm.f.) Becherer and marginally also Figure 3. Iconography of Diplotaxis kohlaanensis, based on material from Ethiopia. Drawing by Adriana Santanello.  8Cambria S et al Primula verticillata Hochst. subsp. simensis (Hochst.) W.W.Sm. & Forrest [=Evotrochis simensis (Hochst.) Fırat & Lidén]. Conservation The population of D. kohlaanensis entirely falls within the Simien National Park, a protected area created in 1969, a period when 80% of the Park was subjected to human exploitation through livestock grazing, cultivation and settlements (Debonnet et al. 2006). Actually, this is still threatened by human activities, particularly grazing and logging (Jacob et al. 2016), further aggravated by the recent war events which led to a severe reduction of the wooded areas due to coppicing and fires, as highlighted by Meaza et al. (2025) for other mountains of northern Ethiopia. For this reason, the Simien Mountain National Park has been listed as a World Heritage Site in Danger since 1997. Despite this, the vertical cliffs are poorly affected by human disturbance due to their inaccessibility and, therefore, they represent the bestpreserved environments of this area. The population of D. kohlaanensis contains a very low number of individuals (roughly estimated in ca. 100 mature plants) that, even if not immediately threatened, at this stage, we do not know how the species would respond to global warning. By using the Geospatial Conservation Assessment Tool (Bachman et al. 2011), the extent of occurrence (EOO) is calculated to be 0.028 km , while the area of occupancy (AOO) is 4 km . Following the IUCN Criteria at global and regional level (IUCN 2001, IUCN 2003), with the estimated EOO less than 100 km , an AOO less than 10 km , the conservation status of D. kohlaanensis for Ethiopia has been classified as Endangered at regional level (EN reg: D) according to criterion D. Biology Flowering and fruiting during the dry season from November to March. Identification keys Key to the taxa belonging to Diplotaxis harra species complex 1Annual or rarely perennial herb, loosely branched, with densely hairy leaves and stems, leaves not fleshy with 5–15 pairs of teeth Diplotaxis harra – Perennial suffruticose plant, with a basal woody rootstock, densely branched, with glabrous or glabrescent leaves and stems, leaves fleshy with 1–6 pairs of teeth or pinnatipartite 2 2 Flowering branches flexuosus, leaves with dentate or lobed margins, petals 7–9 mm long, shorter than flower pedicel, dark yellow, siliques hanging at fruiting, flowers not overtopping the buds 3 2 2 2 2 First record of Diplotaxis kohlaanensis (Brassicaceae) for the eastern ... 9 D. harra D. lagascana D. crassifolia D. kohlaanensis Flowering branches length (cm) 60 80 100 300 Inflorescence erect erect flexuous and hanging erect Petal colour dark yellow dark yellow dark yellow pale yellow Petal length (mm) 7–9 7–9 6–10 10–14 Siliques size (mm) 10–50 × 2–3 25-40 × 1.5–3.5 30–60 × 2–3 12–40 × 2.5–3.2 Beak length (mm) 1.5–2 1–2 1–2 1.5–2 The two European species of the D. harra complex, namely D. crassifolia and D. lagascana, show a greater morphological affinity with D. kohlaanensis, especially for the subshrubby habit and the glabrous (or glabrescent) and fleshy leaves. D. lagascana, a Spanish endemism often treated at subspecific rank (sub D. harra (Forssk.) Boiss. subsp. lagascana (DC.) O.Bolòs & Vigo) is easily distinguishable for having pinnatipartite to pinnatifidous leaves (Castroviejo et al. 1993). As concerns D. crassifolia [=D. harra (Forssk.) Boiss. subsp. crassifolia (Raf.) Maire], a Sicilian endemism (Pignatti et al. 2019, Brullo and Brullo 2020), wrongly recorded also for North Africa (Maire 1965, PottierFigure 5. Main morphological features of the taxa belonging to the Diplotaxis harra group - flowering branches (1); Leaf (2); Silique (3): A D. kohlaanensis; B D. crassifolia; C D. lagascana; D D. harra. Drawings by Rosaria Di Cicca.  16 Cambria S et al Alapetite 1979, Fennane 1999), shows a similar leaf blade, often dentate with 1–6 teeth for side. However, it is easily distinguished from D. kohlaanensis by its long, flexible and pendulous flowering branches and by its flowers with dark yellow and much shorter petals (6-10 mm), always shorter than the peduncles. In conclusion, the species at issue is very well distinguishable from the other taxa of the D. harra group, not only for its morphology, but also for its ecological behaviour and geographical distribution. Therefore, the discovery of this specie in Ethiopia has a remarkable phytogeographic value, since it is the first record of a Diplotaxis species in Ethiopia and, likely most interesting, confirms the phytogeographic relationships between the Ethiopian highlands and the Arabian Peninsula mountains. Our investigations on the Afromontane and Afroalpine species with an East AfricanArabian distribution (i.e. amphi-Red Sea taxa) occurring in the Simien Mts. highlight the clear prevalence of perennial, herbaceous or woody species, mainly linked to the Afromontane grasslands and woodlands. This is due to the lack of mountains in the Arabian Peninsula higher than 3,600 m a.s.l., not allowing the presence of a significant Afroalpine flora typical of the highest peaks of the Simien Mts.. Therefore, the mountain flora in common is mostly represented in the altitudinal belt covered by Erica woods, shrubs and secondary grasslands. Conversely, the significant occurrence of chamaephytes must be highlighted showing this distribution in vertical cliffs even at altitudes typical of the Afroalpine belt. In fact, this environment represents a well-known conservative and stable habitat (Larson et al. 2000, García et al. 2020, Sangüesa‐ Barreda et al. 2022, Múgica Carnicero et al. 2024), where, due to the minor human disturbance and the peculiar microclimate, ancient species, often endemic, have been preserved, providing precious evidence of a flora which have now largely disappeared in the nearby areas. In this perspective, Diplotaxis kohlaanensis can be interpreted as a relict species, linked to particularly cool and humid microclimate typical of high-altitude north-exposed cliffs. Furthermore, it shows some archaic features within the Diplotaxis genus, such as the woody habit (Lems 1960, Bramwell 1972, Cronk 2006, Cronk 2008, Lens et al. 2013), suggesting a potential ancestry compared to some allied Mediterranean herbaceous species, as already highlighted by Pignatti (1979) and by Bramwell (1976) for some Macaronesian-African taxa Bramwell (1976). Actually, the phytogeographical affinities between the Mediterranean area and the Horn of Africa have already been highlighted by several authors (Balfour 1888, Gillett 1941, Lavranos 1975, Fici 1991), particularly for the northern Somali escarpment, an area with several taxa having close Mediterranean allies. According to Wickens (1975), the southern Arabian Peninsula and eastern Africa represented an important centre of refuge, speciation and radiation of Holarctic taxa during the glacial phases of Quaternary. Even today, these species strongly characterise the flora of the Ethiopian plateau, which, compared to other mountain ranges of eastern Africa (Hedberg 1957, Hedberg 1964, Hedberg 1969, Bussmann 2006, Cambria et al. 2024) shows a lower incidence of the typical Afroalpine flora and a more significant presence of the Holarctic element. In this frame, the discovery of D. kohlaanensis suggests the role of the high altitude cliffs of the Siemen Mts. as a refuge habitat for several species with northern affinities, whose origin probably date back to the glacial phases of Pleistocene when, as a result of a relatively cool and humid First record of Diplotaxis kohlaanensis (Brassicaceae) for the eastern ... 17 climate, numerous species migrated from the north through the Red Sea corridor reaching the Arabian Peninsula and the Horn of Africa. This origin can be postulated also for other species growing in the same rupicolous habitat of D. kohlaanensis, such as Dianthus longiglumis Delile, Primula verticillate Forssk., Stachys richardiana R.Kr. Singh, Sonchus melanolepis Fresen, Arabis alpina L. etc. As concerns Aeonium leucoblepharum Webb ex A.Rich., frequent in the same environments, its marked geographical isolation from all other species of its genus should be considered as the effect of a long-distance dispersal during the Pleistocene, rather than as the result of older ancient phytogeographic connections between the Macaronesian Islands and East Africa (Mort et al. 2002). Further research in the Siemen Mts. escarpment may lead to other important floristic findings, also complemented by the most recent technological tools such as drones, which have proven particularly useful in the investigation of similar inaccessible vertical cliffs (Porrovecchio et al. 2024, Tavilla et al. 2024, Wagner et al. 2024). Likewise, phylogenetic studies aiming at clarifying the relationships between D. kohlaanensis and the other taxa of D. harra complex are highly desirable. Acknowledgements This investigation was financially supported by the research programme (PIA.CE.RI. 2024-2026 cod. 22722132189) funded by the University of Catania. We thank Rosaria Di Cicca for the realisation of the iconographies of Fig. 5. References • Armitage S, Jasim S, Marks A, Parker A, Usik V, Uerpmann H (2011) The Southern Route “Out of Africa”: Evidence for an early expansion of modern humans into Arabia. Science 331 (6016): 453‑456. https://doi.org/10.1126/science.1199113 • Axelrod D (1975) Evolution and biogeography of Madrean-Tethyan sclerophyll vegetation. Annals of the Missouri Botanical Garden 62 (2). https://doi.org/10.2307/2395199 • Bachman S, Moat J, Hill A, de la Torre J, Scott B (2011) Supporting Red List threat assessments with GeoCAT: geospatial conservation assessment tool. ZooKeys 150: 117‑126. https://doi.org/10.3897/zookeys.150.2109 • Balfour IB (1888) Botany of Socotra. Nature 39: 99‑100. https://doi.org/10.1038/039099a0 • Bar-Yosef O (1987) Pleistocene connexions between Africa and Southwest Asia: an archaeological perspective. The African Archaeological Review 5 (1): 29‑38. https:// doi.org/10.1007/bf01117080 • Bramwell D (1972) Endemism in the flora of the Canary Islands. In: Valentin DH (Ed.) Taxonomy, phytogeography and evolution. Academic Press, London, 431 pp. • Bramwell D (1976) The endemic flora of the Canary Islands. In: Kunkel G (Ed.) Biogeography and ecology in the Canary Islands. The Hague, Junk, 511 pp. • Bramwell D (1985) Contribución a la biogeografia de las Islas Canarias. Botanica Macaronésica 14: 3‑34. • Brinkmann K, Patzelt A, Dickhoefer U, Schlecht E, Buerkert A (2009) Vegetation patterns and diversity along an altitudinal and a grazing gradient in the Jabal al Akhdar mountain 18 Cambria S et al range of northern Oman. Journal of Arid Environments 73 (11): 1035‑1045. https://doi.org/ 10.1016/j.jaridenv.2009.05.002 • Brullo C, Brullo S (2020) Flora endemica illustrata della Sicilia. Laruffa Editore, 441 pp. • Bussmann RW (2006) Vegetation zonation and nomenclature of African Mountains - An overview. Lyonia 11 (1): 41‑66. • Cambria S, Minissale P, Tavilla G (2024) Phytosociological Investigations on the Afroalpine Vegetation of the Ruwenzori Mountains (Uganda). Land 13: 1752. https:// doi.org/10.3390/land13111752 • Castroviejo S, Aedo C, Campo CG, Lainz M, Montserrat P, Morales R, Garmendia FM, Feliner GN, Rico E, Talavera S, Villar L (1993) Flora Iberica. Plantas vasculares de la Península Ibérica e Islas Baleares. Vol. IV Cruciferae-Monotropaceae. Real Jardín Botánico, Madrid, 730 pp. • Cronk QCB (2006) History of the endemic flora of St. Helena: A relictual series. New Phytologist 105 (3): 509‑520. https://doi.org/10.1111/j.1469-8137.1987.tb00888.x • Cronk QCB (2008) Relict floras of Atlantic islands: patterns assessed. Biological Journal of the Linnean Society 46: 91‑103. https://doi.org/10.1111/j.1095-8312.1992.tb00852.x • Debonnet G, Melamari L, Bomhard B (2006) Reactive monitoring mission to Simen Mountains National Park. Joint World Heritage Centre-IUCN monitoring mission to Simen Mountains National Park World Heritage property. UNESCO, Paris. • Demissew S, Friis I, Nordal I, Bürger AM (2006) Disjunctions in the African Flora as seen from the Flora of Ethiopia and Eritrea. In: Ghazanfar SA, Beentje HJ (Eds) Taxonomy and ecology of African plants, their conservation and sustainable use. Kew Royal Botanic Gardens, Kew, 811 pp. • Edwards S, Tadesse M, Demissew S, Hedberg I (2000) Flora of Ethiopia and Eritrea, Vol. 2, Part 1. Uppsala University, Addis Ababa. • Edwards S, Hedberg I (2009) Flora of Ethiopia and Eritrea, vol 1-8. Uppsala University, Addis Ababa. • Engler A (1879) Versuch einer Entwicklungsgeschichte der Pflanzenwelt, insbesondere der Florengebiete seit der Tetiar periode. I. Die extratropischen Gebiete der nordlichen hemisphare. Wilhem Engelmann Verlag, Lepzig. • Fennane M (1999) Diplotaxis DC. In: Fennane M, Tattou MI, Mathez J, Ouyahya A, Oualidi JE (Eds) Flore pratique du Maroc. 1. Institut Scientifique, Université Mohammed V, Rabat, 558 pp. • Fici S (1991) Floristic relations between eastern Africa and the Mediterranean region with special references to Northern Somalia. Flora Mediterranea 1: 175‑185. • Franzke A, Sharif Samani B, Neuffer B, Mummenhoff K, Hurka H (2017) Molecular evidence in Diplotaxis (Brassicaceae) suggests a Quaternary origin of the Cape Verdean flora. Plant Systematics and Evolution 303 (4): 467‑479. https://doi.org/10.1007/ s00606-016-1384-5 • Friis I (1980) The taxonomy and distribution of Mimusops laurifolia (Sapotaceae). Kew Bulletin 35 (4). https://doi.org/10.2307/4110174 • García MB, Domingo D, Pizarro M, Font X, Gómez D, Ehrlén J (2020) Rocky habitats as microclimatic refuges for biodiversity. A close-up thermal approach. Environmental and Experimental Botany 170 https://doi.org/10.1016/j.envexpbot.2019.103886 • Ghazanfar SA (2024) Biogeography and conservation in the Arabian Peninsula: A present perspective. Plants 13: 2091. https://doi.org/10.3390/plants13152091 First record of Diplotaxis kohlaanensis (Brassicaceae) for the eastern ... 19 • Gillett JB (1941) The plant formations of Western British Somaliland and the Harar Province of Abyssinia. Bulletin of Miscellaneous Information (Royal Gardens, Kew) 1941 (2). https://doi.org/10.2307/4102534 • Gómez-Campo C (2011) Biology of Brassica coenospecies. Elsevier Science, Amsterdam, 504 pp. • Hedberg O (1957) Afroalpine vascular plants. A taxonomic revision. Symbolae Botanicae Upsalienses 15 (1): 1‑411. • Hedberg O (1961) Monograph of the genus Canarina L. (Campanulaceae). Svensk Botanisk Tidskrift 55: 17‑62. • Hedberg O (1964) Features of Afroalpine plant ecology. Swedish Science Press, Stockholm, 144 pp. • Hedberg O (1969) Evolution and speciation in tropical high mountain flora. Biological Journal of the Linnean Society 1: 135‑149. https://doi.org/10.1111/j. 1095-8312.1969.tb01816.x • Hegazy A, Lovett-Doust J (2016) Plant ecology in the Middle East. Oxford University Press, Oxford, 339 pp. https://doi.org/10.1093/acprof:oso/9780199660810.001.0001 • Hurni H, Stähli P (1982) Hochgebirge von Semien, Äthiopien: Klima und Dynamik der Höhenstufung von der letzten Kaltzeit bis zur Gegenwart = Simen Mountains, Ethiopia: climate and the dynamics of altitudinal belts from the last cold period to present day. Geographische Gesellschaft Bern https://doi.org/10.5169/seals-960241 • Hurni H (1988) Degradation and conservation of the resources in the Ethiopian Highlands. Mountain Research and Development 8 https://doi.org/10.2307/3673438 • IUCN (2001) Red List Categories and Criteria: Version 3.1. 2. IUCN, Gland, Switzerland and Cambridge, UK, 32 pp. • IUCN (2003) Guidelines for application of IUCN Red List criteria at regional levels: Version 3.0. IUCN. IUCN • Jacob M, Frankl A, Hurni H, Lanckriet S, De Ridder M, Guyassa E, Beeckman H, Nyssen J (2016) Land cover dynamics in the Simien Mountains (Ethiopia), half a century after establishment of the National Park. Regional Environmental Change 17 (3): 777‑787. https://doi.org/10.1007/s10113-016-1070-8 • Kieffer B, Arndt N, Lapierre H, Bastien F, Bosch D, Pecher A, Yirgu G, Ayalew D, Weis D, Jerram D, Keller F, Meugniot C (2004) Flood and shield basalts from Ethiopia: Magmas from the African Superswell. Journal of Petrology 45 (4): 793‑834. https://doi.org/10.1093/ petrology/egg112 • Kürschner H (1998) Biogeography and Introduction to Vegetation. Vegetation of the Arabian Peninsula63‑98. https://doi.org/10.1007/978-94-017-3637-4_4 • Larson DW, Matthes U, Kelly PE (2000) Cliff ecology: Pattern and process in cliff ecosystems. Cambridge University Press, Cambridge, 360 pp. https://doi.org/10.1017/ CBO9780511525582 • Lavranos JJ (1975) Note on the northern temperate element in the flora of the EthioArabian region. Conservatoire et Jardin Botaniques de la Ville de Genève https://doi.org/ 10.5169/seals-895494 • Lems K (1960) Botanical notes on the Canary Islands. II. The evolution of plant forms in the islands: Aeonium. Ecology 41: 1‑17. https://doi.org/10.2307/1931934 • Lens F, Davin N, Smets E, Arco Md (2013) Insular woodiness on the Canary Islands: a remarkable case of convergent evolution. International Journal of Plant Sciences 174: 992‑1013. https://doi.org/10.1086/670259 20 Cambria S et al • Maire R (1965) Flore de l′Afrique du Nord. XII. Éditions Paul Lechevallier, Paris. • Martinez-Laborde JB (1988) Estudio Sistemático del Género Diplotaxis DC. (Cruciferae, Brassiceae). Universidad Politécnica de Madrid • Martínez-Laborde JB (1991) Diplotaxis harra (Forsskal) Boiss. in Europe. Botanical Journal of the Linnean Society 106: 112‑115. • Martín JP, Sánchez-Yélamo MD (2000) Genetic relationships among species of the genus Diplotaxis (Brassicaceae) using inter-simple sequence repeat markers. Theoretical and Applied Genetics 101 (8): 1234‑1241. https://doi.org/10.1007/s001220051602 • Masresha G (2022) Composition and endemicity of plant species in Simien Mountains National Park Flora, North Gondar, Northwestern Ethiopia. Ethiopian Journal of Natural and Computational Sciences 2 (1): 301‑310. • Meaza H, Ghebreyohannes T, Tesfamariam Z, Gebresamuel G, Demissie B, Gebregziabher D, Nyssen J (2025) The effects of armed conflict on natural resources and conservation measures in Tigray, Northern Ethiopia. International Soil and Water Conservation Research 13 (2): 463‑474. https://doi.org/10.1016/j.iswcr.2024.11.004 • Melese GT, Tsegay BA, Kassa GM, Kuratie GB (2018) Patterns of plant community formation and vegetation structure in the Afro-Alpine vegetation of Simien Mountains National Park, Ethiopia. The International Journal of Biotechnology 7 (1): 31‑43. https:// doi.org/10.18488/journal.57.2018.71.31.43 • Miller AG, Nyberg J (1994) Studies in the Flora of: XXVII. Some new taxa from the Arabian Peninsula. Edinburgh Journal of Botany 51 (1): 33‑47. https://doi.org/10.1017/ S0960428600001694 • Miller AG, Cope TA (1996) Flora of the Arabian Peninsula and Socotra. Vol. 1. Edinburgh University Press, Edinburgh, 586 pp. • Mort ME, Soltis DE, Soltis PS, Francisco-Ortega J, Santos-Guerra A (2002) Phylogenetics and evolution of the Macaronesian clade of Crassulaceae inferred from nuclear and chloroplast sequence data. Systematic Botany 27: 271‑288. • Múgica Carnicero A, Garcia M, Miranda H (2024) Survival patterns and population stability of cliff plants suggest high resistance to environmental variability. Basic and Applied Ecology 80: 128‑13. https://doi.org/10.32942/x2k60z • Oberprieler C, Zimmer C, Bog M (2017) Are there morphological and life-history traits under climate-dependent differential selection in S Tunesian Diplotaxis harra (Forssk.) Boiss. (Brassicaceae) populations? Ecology and Evolution 8 (2): 1047‑1062. https:// doi.org/10.1002/ece3.3705 • Oliver D (1868) Flora of Tropical Africa. 1. Reeve and co., Ashford, 479 pp. • Petraglia M, Haslam M, Fuller D, Boivin N, Clarkson C (2010) Out of Africa: new hypotheses and evidence for the dispersal of Homo sapiens along the Indian Ocean rim. Annals of Human Biology 37 (3): 288‑311. https://doi.org/10.3109/03014461003639249 • Pignatti S (1979) Plant geographical and morphological evidences in the evolution of the Mediterranean flora (with particular reference to the Italian representatives). Webbia 34 (1): 243‑255. https://doi.org/10.1080/00837792.1979.10670170 • Pignatti S, Guarino R, La Rosa M (2019) Flora d'Italia vol. 1-4. Edagricole, Milano. • Pignone D, Martínez-Laborde J (2010) Diplotaxis. Wild Crop Relatives: Genomic and Breeding Resources137‑147. https://doi.org/10.1007/978-3-642-14871-2_7 • Porrovecchio M, Cambria S, Bacilliere G, Barone G, Crisafulli A, Di Gristina E, Di Pasquale C, Di Mauro M, Domina G, Luchino F, Marici C, Miraglia G, Tavilla G, Sciandrello S (2024) Using drone imagery and group field activities for an in-depth First record of Diplotaxis kohlaanensis (Brassicaceae) for the eastern ... 21 investigation of the vascular flora: a case study in the Rocca di Novara Massif (NE Sicily, Italy). Italian Botanist 18: 13‑28. https://doi.org/10.3897/italianbotanist.18.127209 • Pottier-Alapetite G (1979) Flore de la Tunisia Angiospermes-Dicotyledones. Imprimerie Officielle de la Republique Tunisienne, Tunisi, 651 pp. • POWO (2025) Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. https://powo.science.kew.org/ • Pradhan AK, Prakash S, Mukhopadhyay A, Pental D (1992) Phytogeny of Brassica and allied genera based on variation in chloroplast and mitochondrial DNA patterns: molecular and taxonomic classifications are incongruous. Theoretical and Applied Genetics 85: 331‑340. https://doi.org/10.1007/bf00222878 • Puff C, Nemomissa S (2001) The Simen Mountains (Ethiopia): Comments on Plant Biodiversity, Endemism, Phytogeographical Affinities and Historical Aspects. Systematics and Geography of Plants 71 (2). https://doi.org/10.2307/3668732 • Puff C, Nemomissa S (2005) Plants of the Simen A Flora of the Simen Mountains and Surroundings, Northern Ethiopia. National Botanic Garden of Belgium, Meise, 258 pp. • RStudio Team (2020) RStudio: Integrated Development Environment for R. RStudio, PBC. Versione 2024.09.1+394 (2024.09.1+394). http://www.rstudio.com/ • Rustan Ø (2008) Revision of the genus Diplotaxis (Brassicaceae) in the Cape Verde Islands, W Africa. Nordic Journal of Botany 16 (1): 19‑50. https://doi.org/10.1111/j. 1756-1051.1996.tb00213.x • Sangüesa‐Barreda G, García‐Cervigón A, García‐Hidalgo M, Rozas V, Martín‐Esquivel JL, Martín‐Carbajal J, Martínez R, Olano JM (2022) Vertical cliffs harbor millennia-old junipers in the Canary Islands. Ecology 103 (4). https://doi.org/10.1002/ecy.3633 • Schettino A, Macchiavelli C, Pierantoni PP, Zanoni D, Rasul N (2016) Recent kinematics of the tectonic plates surrounding the Red Sea and Gulf of Aden. Geophysical Journal International 207 (1): 457‑480. https://doi.org/10.1093/gji/ggw280 • Schettino A, Macchiavelli C, Rasul NA (2019) Plate motions around the Red Sea since the Early Oligocene. Geological Setting, Palaeoenvironment and Archaeology of the Red Sea203‑220. https://doi.org/10.1007/978-3-319-99408-6_9 • Schulz O (1919) Diplotaxis. In: Engler A (Ed.) Das Pflanzenreich IV. Wilhelm Engelmann, Leipzig. • Tavilla G, Crisafulli A, Minissale P, Tomaselli V, Adamo M (2024) Use of the drone for cost-effective surveys in Natura 2000 protected areas: a case study on monitoring plant diversity in Sicily (Italy). Land 13 (6): 804. https://doi.org/10.3390/land13060804 • Thiers B (2025) Index herbariorum: A global directory of public herbaria and associated staff. New York Botanical Garden’s Virtual Herbarium. http://sweetgum.nybg.org/ih/ • Thiv M, Thulin M, Hjertson M, Kropf M, Linder HP (2010) Evidence for a vicariant origin of Macaronesian–Eritreo/Arabian disjunctions in Campylanthus Roth (Plantaginaceae). Molecular Phylogenetics and Evolution 54 (2): 607‑616. https://doi.org/10.1016/j.ympev. 2009.10.009 • Thulin M (1993) Flora of Somalia. Pteridophyta; Gymnospermae; Angiospermae (Annonacae-Fabaceae). Vol. 1. Royal Botanic Gardens, Kew, 497 pp. • Thulin M (1994) Aspects of disjunct distributions and endemism in the arid parts of the Horn of Africa, particularly Somalia. In: Seyani JH, Chikuni AC (Eds) Proceedings of the XIIIth Plenary Meeting of AETFAT, Zomba, Malawi, Vol. 2. National Herbarium and Botanic Gardens of Malawi, Zomba. 22 Cambria S et al • Wagner W, Weller S, Sakai A, Nyberg B, Wood K (2024) Schiedea waiahuluensis (Caryophyllaceae), an enigmatic new species from Kaua'i, Hawaiian Islands and the first species discovered by a drone collection system. PhytoKeys 247: 111‑121. https:// doi.org/10.3897/phytokeys.247.130241 • Warwick S, Hall JC (2009) Phylogeny of Brassica and wild relatives. In: Gupta SK (Ed.) Biology and breeding of Crucifers. Surinder Kumar Gupta, Chata. • Warwick SI, Black LD, Aguinagalde I (1992) Molecular systematics of Brassica and allied genera (Subtribe Brassicinae, Brassiceae) — chloroplast DNA variation in the genus Diplotaxis. Theoretical and Applied Genetics 83: 839‑850. https://doi.org/10.1007/ bf00226706 • White F (1978) The Afromontane Region. In: Werger MJ (Ed.) Biogeography and ecology of southern Africa. The Hague, Junk. https://doi.org/10.1007/978-94-009-9951-0_11 • Wickens GE (1975) Changes in the climate and vegetation of the Sudan since 20 000 B.P. Boissiera 24: 43‑65. https://doi.org/10.5169/seals-895493 • Wickham H (2016) ggplot2. Springer https://doi.org/10.1007/978-0-387-98141-3 • Wickham H, Vaughan D, Girlich M (2017) tidyr: Easily Tidy Data. CRAN: Contributed Packages https://doi.org/10.32614/cran.package.tidyr • Zohary M (1966) Flora Palaestina, part one. Israel Academy of Sciences and Humanities, Jerusalem, 364 pp. First record of Diplotaxis kohlaanensis (Brassicaceae) for the eastern ... 23