Ceropegia longirostris sp. nov. (Apocynaceae–Asclepiadoideae) from Ethiopia and Kenya

The new species Ceropegia longirostris Thulin, M.G.Gilbert & Kaariye is described, illustrated and mapped. It is known from two localities, one on gypsum in the Somali National Regional State (Ogaden) in southeastern Ethiopia and one, based on a photographic record, from just east of Lake Turkana in northwestern Kenya. The new species is a member of C. sect. Phalaena H.Huber, and is distinctive by having flowers with the corolla glabrous outside and apically with a long narrowly clavate beak abruptly delimited from the rest of the corolla, and with each lobe of the corolla having a prominent wart-like blackish projection near the tip on the inside.


Introduction
During field work in the Somali National Regional State (Ogaden) in eastern Ethiopia in May 2006 andFebruary 2007, two of us (MT andHYK) found a distinctive new species of Ceropegia L. in a small outcrop of gypsum east of Kebri Dehar.The species was subsequently described as C. gypsophila Thulin (2009).However, another species of Ceropegia was also seen in the same locality, but this was not in flower at the time and was left unidentified.
More than 10 years later, HYK sent images to MT from the locality, now with flowering plants of both Ceropegia gypsophila and the unidentified species.This latter plant was judged by MT to be another new species, and HYK subsequently collected a small sample of flowers and leaves in spirit that was sent to MT.
MT, in turn, informed MGG, author of the account of Ceropegia in Flora of Ethiopia and Eritrea (Gilbert 2003), about this plant and passed on one of the images of it.MGG replied that he recognized the plant, not from Ethiopia, but from images that had been sent to him by the late Francis H. Brown, a geologist who had found it in June, 2012, in connection with archeological work near Ileret in northwestern Kenya.This species, now known from two localities quite far apart, one in Ethiopia and one in Kenya, is described below as C. longirostris.Francis Brown's collections are  Herbarium,Royal Botanic Gardens,Kew,Richmond,Surrey,England.-H.Y. Kaariye, Kebri Dehar, Ethiopia.normally found in EA (Polhill and Polhill 2015), but no corresponding specimen from Ileret could be traced there in July 2021 (Mutuku Musili, pers. comm.).The Kenyan record of the species is therefore based on photographs only.A species that differs from Ceropegia somalensis Chiov.by having a corolla that is glabrous outside (versus shortly and densely pubescent all over the outer surface), 7-8 mm (versus 12-16 mm) wide at the mouth, with wart-like projections ca 1.3 mm long on the inside of the corolla lobes below their point of fusion (versus sometimes having smaller or rudimentary knobs), the lobe margins recurved and auriculate at the sinus (versus flat), and with the tips of the corolla lobes twisted together or closely cohering to form a narrowly clavate, 16-20 mm long beak that is abruptly delimited from the rest of the corolla and sometimes more or less geniculate at the base (versus a beak more gradually delimited and loosely twisted above to form a

Description
Climber up to several meters long, with branched fibrous roots; stems succulent, terete, twining, 2-5 mm in diam., glabrous, glaucous, greyish green.Leaves opposite; petiole 8-15 mm long, cylindrical and with a furrow above, glabrous; blade lanceolate to narrowly ovate, 25-60 × 10-18 mm, cuneate to truncate or slightly cordate at base, acute to acuminate at apex, glabrous except for sparsely papillose margin, dark green, with midrib protruding beneath and lateral veins 3-5 pairs, margins flat or ± revolute.Flowers 5-merous in extra-axillary few-flowered umbel-like cymes; peduncle 5-10 mm long, glabrous; pedicel 7-8 mm long, ca 1 mm in diam., terete, glabrous, greyish green; bracts and bracteoles triangular-acuminate, 0.5-1.5 mm long, glabrous.Sepals linear-lanceolate, 3-4 mm long, ca 0.8 mm wide at the base, acuminate, ± appressed to base of corolla, glabrous.Corolla ascending, ± strongly curved near the base, glabrous outside, 37-40 mm long in total, lower part tubular, with lobes remaining fused at tips and with gaping openings in between, above point of fusion the lobes are ± tightly twisted together or closely cohering into a narrow beak that is abruptly delimited from the rest of the corolla and nearly half as long as the total length of the flower; tube ca 18 mm long, pale greyish green with dull purplish blotches outside, particularly in upper expanded part; basal chamber ovoid, 4.5-5.0mm wide and ca 5 mm long, not separated from rest of tube by an annulus, glabrous inside; tube above basal chamber with lower part cylindrical, 2.5-3.0 mm wide and ca 6 mm long, glabrous inside, its upper part funnel-shaped, ca 7 mm long, gradually widening to 7-8 mm at the mouth, pubescent with long white downwardly pointing hairs inside; corolla lobes ca 5 mm long and 4.0-4.5 mm wide at the broadly triangular base, longitudinally folded with recurved margins and slightly raised sinus, reflexed above point of fusion to form a depression around the apical extension, pale greyish green with dull purplish blotches outside and with purplish reticulum inside, with long white hairs along midrib near the base inside, each lobe with a blackish glabrous wart-like projection ca 1.3 mm long and 1 mm wide, directed downwards and inserted just below the point of fusion of the lobes; beak at top of corolla narrowly clavate, 16-20 mm long and ca 1.5 mm or occasionally up to 2 mm wide, dull purplish, glabrous, upright and straight or ± geniculate at the base and ± curved.Corona gynostegial, sessile; outer corona cup-shaped with spreading, broadly triangular, ca 1 mm long interstaminal lobes bifid at the apex, with sparsely pubescent margin; inner corona of linear ca 3 mm long staminal lobes, connivent over the style cap and with outcurved tips, glabrous.Follicles slender, widely divergent, ca 15 cm long (estimated from Fig. 3B); seeds unknown.

Distribution and habitat
Ceropegia longirostris is known from only two localities, one in Ethiopia and one in Kenya (Fig. 4) and some 900 km apart.The type locality in Ethiopia is situated east of Kebri Dehar in the Somali National Regional State (previously Harerge Region) in an area called Ceelxaar.The species is found in a small gypsum outcrop surrounded by silty or sandy ground, in a vegetation of open Senegalia-Vachellia-Commiphora bushland at an elevation of 500-550 m a.s.l.The locality is also the type locality of C. gypsophila Thulin (2009) and Commicarpus ogadenensis Thulin (2021), and other more or less local gypsum endemics found there are Kleinia gypsophila Lebrun & Stork and Euphorbia suborbicularis Thulin.
The locality in Kenya, Ileret just east of Lake Turkana, is situated within the Sibiloi National Park.This is an UNESCO World Heritage Site since 1997, famous for its important archaeological sites, such as Koobi Fora, with rich findings of fossils of early hominids.We have no direct information on the habitat of the Kenyan locality of Ceropegia longirostris, but presumably it is open bushland on gypseous ground at ca 400 m a.s.l.It is very likely that further populations of the species exist and it should be searched for in other areas of gypsum at similar elevations in southern Ethiopia and northern Kenya.

Similar species
Ceropegia longirostris is a member of C. sect.Phalaena H.Huber (Bruyns et al. 2017), a section that is very well represented in the Horn of Africa.The nearest relative is probably C. somalensis Chiov., a species originally described from southern Somalia (Chiovenda 1916), but also known from northern Somalia (Gilbert 2006), Ethiopia (Gilbert 2003), Kenya (Masinde 2012), as well as from Yemen (Bruyns 1989) and Saudi Arabia (Collenette 1999).Ceropegia somalensis has flowers with the tips of the corolla lobes often, but not always, twisted together into a clavate beak and, furthermore, the corolla lobes are sometimes furnished with a more or less prominent knob on the inside below their point of fusion (Masinde 2012: Fig. 69.3).The structure of the corona is also very similar in C. somalensis and C. longirostris.Flowers of C. somalensis, from a locality ca 170 km from the type locality of C. longirostris, are shown for comparison in Fig. 5A.This shows the general similarity in the shape of the corolla, but in this form of C. somalensis, the knobs on the inside of the corolla lobes are missing.
Ceropegia longirostris differs clearly from the widespread and variable C. somalensis by having a corolla that is glabrous outside (versus shortly and densely pubescent all over the outer surface), 7-8 mm (versus 12-16 mm) wide at the mouth, with wart-like projections ca 1.3 mm long (Fig. 1C, 2) on the inside of the corolla lobes below their point of fusion (versus sometimes having smaller or rudimentary knobs), and with the tips of the corolla lobes more or less tightly twisted together or closely cohering to form a narrowly clavate (Fig. 1), 16-20 mm long beak that is abruptly delimited from the rest of the corolla (versus a beak more gradually delimited and loosely twisted above to form a secondary upper 'cage' (Fig. 5A) or occasionally uppermost part of corolla lobes absent).There is also a distinct difference in colouration, with the flowers of C. somalensis always lacking any trace of the purplish colours of the new species.Finally, whereas C. longirostris seems confined to areas of gypsum, there is no   Finally, also Ceropegia gypsophila, the species that cooccurs with C. longirostris at the type locality, has corolla lobes that form a beak at the tip and a corona structure similar to that in C. longirostris.However, C. gypsophila has a very different, parachute-like corolla (Fig. 5B), without wart-like projections below the point of fusion of the corolla lobes, but instead with an umbrella-like structure on the inside of the corolla roof formed by five, stalked, ovate, fleshy lobes.The parachute-like corolla of C. gypsophila much resembles that of C. sandersonii Decne.ex Hook.f. in southern Africa, and these two species were believed to be close relatives by Thulin (2009).However, the similarity is superficial and, whereas C. gypsophila is a member of C. sect.Phalaena, C. sandersonii is currently placed in C. sect.Radicantiores Bruyns (Bruyns et al. 2017).

Figure 1 .
Figure 1.Ceropegia longirostris sp.nov. at type locality (A) flower with beak of corolla bent at the base and curved, (B) flower with beak upright and straight, (C) detail of flower showing blackish wart-like projections on inside of corolla lobes and abruptly delimited beak.Photographs by Hassan Y. Kaariye.

Figure 2 .
Figure 2. Ceropegia longirostris sp.nov.Corolla opened up to show wart-like projections on inside of corolla lobes just below their point of fusion.Scale = 1 mm.Photograph by Mats Thulin.

Figure 4 .
Figure 4. Map of Horn of Africa, showing distribution of Ceropegia longirostris in Ethiopia and Kenya.