Cystostemon heliocharis (S. Moore) A. G. Mill. & Riedl, 1982

Thulin, Mats & Larsson, Anders, 2021, New country records for species of Boraginaceae and Lamiaceae in the Horn of Africa hotspot, Phytotaxa 513 (1), pp. 62-68 : 62-63

Cystostemon heliocharis (Moore in Baker & Moore 1877: 68) Miller & Riedl (1982: 7)

New specimen record:— ETHIOPIA. Oromia Region, Harerge: 10 km from Lefa Isa on road to Heregel , elev. 1825–1850 m, 12 November 1992, flowering and fruiting, Kuchar & Mahdi Kidar 18428 ( ETH!, UPS!) .

This is a new record for Ethiopia ( Fig. 1 ). The previously unidentified material was included among specimens sent from the South East Rangelands project in Ethiopia to UPS. The collection was made in open shrubland on a northfacing slope of a stony hill.

The genus Cystostemon Balfour (1884: 82) was revised by Miller & Riedl (1982), who recognized 13 species, distributed from the southwestern Arabian Peninsula and Socotra in the north, to Zambia and Angola in the south. Since then, three further species have been described from Angola and Zambia by Martins (1988a, b).

Miller & Riedl (1982) cited material of Cystostemon heliocharis from Yemen and Somalia, and provided a map of the distribution of the species. Thulin (2006a) treated four species, C. heliocharis , C. intricatus Miller & Riedl (1982: 11) , C. somaliensis Miller & Riedl (1982: 8) , and C. virescens Miller & Riedl (1982: 15) in Flora of Somalia, whereas Riedl & Edwards (2006) recorded two species, C. ethiopicus Miller & Riedl (1982: 12) and C. virescens , in Flora of Ethiopia and Eritrea. The revised map for C. heliocharis ( Fig. 1 ) shows that the new Ethiopian record is in close vicinity of localities in northwestern Somalia (Somaliland). A photograph of a plant from a locality in northwestern Somalia is shown in Fig. 2 .

The type of Cystostemon heliocharis is from Somalia, and Miller & Riedl (1982) questioned whether the populations in Yemen should be given formal recognition, mainly on the basis of a difference in flower colour (corolla white or whitish in plants from Yemen, vs. mauve or pink in Somalia). However, the variation in the colour of the corolla is considerable. In Somali material, the corolla is mostly described as pale pink, but sometimes it is said to be pinkish white (Thulin & Warfa 6046, UPS), very pale pink (Mooney 7630, K), whitish (Bally 9679, K), or white (Bally 10833, K). Therefore, there seems to be no ground for a subdivision of the species based on flower colour. The colour of the corolla in the Ethiopian material is not indicated .

Figures

FIGURE 1. Map of the Horn of Africa region, showing the distribution of Cystostemon heliocharis.

FIGURE 2. Cystostemon heliocharis, from northwestern Somalia (Somaliland), ca. 120 km from Erigavo to Burao, 18 Aug 2019. Photograph by Boris Vrškový.