A new species of Emilia (Asteraceae, Senecioneae) from Lower Juba region, Somalia

1 –––––––––––––––––––––––––––––––––––––––– © 2021 The Authors. Nordic Journal of Botany published by John Wiley & Sons Ltd on behalf of Nordic Society Oikos This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Subject Editor: Isabel Larridon Editor-in-Chief: Torbjörn Tyler Accepted 20 April 2021 2021: e03252 doi: 10.1111/njb.03252 2021 e03252

Working up an unidentified part of some collections from the Horn of Africa region made by R. Bavazzano in 1973 and housed at the Centro Studi Erbario Tropicale (Herbarium FT) of the University of Florence, some specimens of Emilia from southernmost Somalia were found which diverged from the only species known in this genus in the area and which could not be identified with the available literature (Jeffrey andBeentje 2005, Thulin 2006). Morphological investigation of the unidentified material and comparison with the known members of Emilia showed it to represent an undescribed taxon, which is described here.

Area of study
The coast between the Juba River and the border of Kenya is little known from a geobotanical point of view. Apart from Chiovenda's notes in his Flora Somala (1929,1932,1936), the only other contribution is by Ciferri (1939) on the coasts and dunes of Benadir.
2 Other information is given by Birch (1963) and Sauer (1965); both these studies are limited to southern Kenya but point out some affinities with the coastal vegetation of southern Somalia.
An annoteted checklist is available for the coastal forests of Kenya (Ngumbau et al. 2020).

Material and methods
The materials for this study come from different collections made in the area of study between 1971 and 1975 by FT herbarium staff.
Some specimens were still unidentified while others were found among specimens of E. bellioides or as Asteraceae sp. in FT herbarium.
Presumably a short-lived perennial, 10-25 cm tall, branching from a 3-5(6) mm thick basal stem showing leaf base remnants or leaf scars along it, also branching from ground/ base; stem usually erect or sometimes procumbent; internodes short, around 1-2 cm.

Eponymy
The epithet refers to this species' habit of growing on coralline sand or on madreporic limestone; the adjective 'corallina' derives from the Latin term for coral 'corallium'.

Ecology, distribution and affinities
Habitat: coastal dunes and madreporic limestone outcrops, 0-10 m a.s.l. The locality of the type collection is situated in the Lower Juba coast, about 20 km south of Chisimaio and 4.5 km south of the Coangiule peninsula. In this coast section the wave action is checked by the almost continuous barrier of the madreporic Bajuni islands which delimit a channel which is around 3-4 km wide and fairly sheltered from winds, especially during the SW monsoon (Pardi 1976a).
The area south of Chisimaio presents low dunes and a rather inconsistent strip of sand followed inland on the rocky madreporic substrate by prostrate bushland (Moggi 1987).
The dunes found in this area differ from the ones in central Somalia and around Mogadishu in being less extensive, relatively small (5-10 m high rarely 20 m) and composed of white calcareous sand, produced by the abrasion of the reef (Pignatti et al. 1987). The sand granulometry is characteristic of organogenic sand in tidal beaches with mediumfine grains without any important mineralogical components (Messana et al. 1977).
The coral reef that constitutes the present coastline (coastal shelf, III in Fig. 1 in Moggi 1987) presents two different aspects: an exposed rock shelf which forms a more or less elevated rock coast, or a small terrace which is covered with sand (Moggi 1987).
According to Pignatti et al. (1987) on the coast near Chisimaio sometimes at the edge of the beach the calcareous reef appears covered on top by a layer of sand, these littoral sandy terraces on limestone are parallel to the coast and host particular vegetation types.
Emilia corallina appears to grow in both these habitats and assumes consequently different growth habit in response to the different edaphic conditions. Plants growing in madreporic sandy soil maintain a low and compact growth while individuals found more inland on rocky substrate have an elongated and stretched appearance.

3
The species seems to grow from the dunal area and troughout the retrodunal plane up to the rocky platform and madrepore outcrops.
Emilia corallina was gathered together with Launaea benadirensis Chiov. and presumably appears to belong to the Panicum pinifolium-Launaea benadirensis community (found on limestone cliffs covered by aeolian sand) and the Justicia-Polycarpaea somalensis community (growing on mobile sand deriving from the costal reefs) which have been observed near Mogadishu by Pignatti et al. (1987, Fig. 3.2) and at Sar Uanle by Moggi (1987). Moggi (1987) considers the latter community very common along the Somalian coast, underlining it has many aspects in common with the vegetation studied at Sar Uanle. 4
Theoretically this species could be present in Kenya as well, at least in areas adjacent the border with Somalia, although the coast in Kenya is somehow different according to Moggi (1987), being sandy and shallow, but with high coral rock cliffs (up to 15 m) immediately behind (from which the sand originates via erosion) and followed inland by a strip of forest (with trees up to 5-10 m tall) at not more than 50-100 m from the high tide limit.
According to Picchi Sermolli's vegetation map (1957) the same situation occurs along part of the Somali coast as well. Friis and Vollesen (1989) report the woodland to be less pronounced in the Chisimaio dunes.
If E. corallina is narrowly associated with the vegetation documented by Fig. 4, it is not likely to reach the Kenyan border and might have a distribution restricted to the area south of Chisimaio.

Comments and further investigations
Most likely the same species is represented by another collection (FT! FT0007407: 0°37′S, 42°27′E, 9-11 Jun 1973 R. Bavazzano s.n.) from the Sar Uanle area, but this time from a rocky plain, with Sterculia and Combretum, instead of the dune area in which the type was found. This plant shows some differences in that the habit as it appears to be more herbaceous and slender, around 25 cm tall, the leaves are smaller and spathulate throughout the plant, the capitula are slightly smaller and more abundant, grouped mostly in 3:s, each head on a peduncle/stalk up to 7 cm long, with their bases arising close together. Florets and achenes appear to be similar.