Dovyalis keniensis (Salicaceae), a new species from the coastal forests of Kenya

Dovyalis keniensis E. V. Williams (Salicaceae) is described as a new species from the coastal forests of Kenya. The species is illustrated, its distribution mapped and conservation status assessed. It is compared with D. mollis (Oliv.) Warb. and D. hispidula Willd. A key to the four species of Dovyalis in Kenya is presented.


Introduction
The genus Dovyalis E. Mey. ex Arn. contains 18 species. It is in the family Salicaceae but was previously placed in Flacourtiaceae (Chase et al. 2002). Dovyalis is found primarily in subtropical and tropical Africa, with one species D. hebecarpa (Gardner) Warb. found in Sri Lanka. The genus was revised by Sleumer (1972) who recognised 15 species and one imperfectly known species. Cheek & Ngolan (2006) described a new species D. cameroonensis from Cameroon and Nigeria and resurrected D. macrocarpa Bamps. The Flora of Tropical East Africa (F.T.E.A.) account of Dovyalis (Sleumer 1975) contains six species and one species named Dovyalis sp. A. This latter species was described in F.T.E.A. from three herbarium specimens as "imperfectly known, should be observed and collected again more completely" (Sleumer 1975: 66). These three specimens were from female plants from three localities along the Kenya coast (Arabuko-Sokoke forest, Gede and Mrima Hill  Sleumer (1972: 89). Dovyalis sp. A sensu Sleumer (1975: 66). Dovyalis sp. nov. sensu Beentje (1994: 106).

RECOGNITION.
Morphologically similar to Dovyalis mollis (Oliv.) Warb. from Angola and the Democratic Republic of Congo but differs in longer axillary spines up to 5 cm (vs up to 2.5 cm long in D. mollis), smaller leaves 1.5 -6.6 × 1 -2.5 cm (vs 6 -11 × 2.4 -4.5 cm), male flowers with longer pedicel 4 -7 mm (vs 3 -5 mm), male tepals smaller 1.5 -2 mm (vs 3 mm) and styles normally 2 (vs 3 -4).  (Mittermeier et al. 2005). This hotspot is threatened by illegal logging, charcoal production, firewood collection and overharvesting of wood for carving (BirdLife International 2013). Mining may become a risk in the near future as titanium has been found underneath Arabuko-Sokoke forest and there are plans to begin mining an area of 64 km 2 in Kwale district (BirdLife International 2013). There is also an open cast mine at Mrima Hills for Niobium Ore, which is expected to expand in the near future (Q. Luke pers. comm. 2015). Diani forest is threatened by clearance for tourist infrastructure, with only 30% of forest remaining at present (Q. Luke pers. comm. 2015).
Six locations for this species are Important Bird and Biodiversity Areas; one has been rated by BirdLife International as under medium threat (Gede Ruins National Monument), three as high threat (Arabuko-Sokoke forest, Dzombo Hill and Mrima Hill) and one as under very high threat (Shimba Hills) (BirdLife International 2016). The main threats listed are drought (Arabuko-Sokoke forest and Mrima Hill), increase in fire frequency and intensity (Dzombo Hill and Shimba Hills), disturbance by recreational activities (Gede) and small scale logging (Shimba Hills). Diani Forest's threat status has not yet been assessed by BirdLife International.
The threats at the remaining location, near to Kakonei town are unknown but the area is developed with housing and some agricultural land.
With the ongoing and future threats to the Kenya coastal forests and restricted EOO and AOO Dovyalis keniensis is assessed using IUCN (2012) criteria as Vulnerable VU B1ab(i,ii,iii,v),B2ab(i,ii,iii,v). There are seven locations and due to the reported threats to coastal forests in Kenya, a continued decline of area, extent and quality of habitat leading to an inferred decline in EOO, AOO and number of mature individuals.
There are some conservation measures as seeds are conserved in ex situ seed banks (at the Royal Botanic Gardens, Kew UK and the Kenya Agricultural Research and Livestock Organisation) and the species occurs in protected areas (Arabuko-Sokoke Forest Reserve, Shimba Hills National Reserve, Dzombo Hill Forest Reserve, Gede Ruins National Monument and Mrima Hill Forest Reserve). PHENOLOGY. Flowering specimens from March to April. Fruiting specimens from March to July with most specimens from June. VERNACULAR NAME. "Mdungatunda" in Giriama language cited in Beentje (1994) and on one herbarium specimen (Trump 109). "Mnao-Mnao" in Swahili recorded on another herbarium specimen (Donald 2324) but not cited in Beentje (1994). USES. The fruits are reported to be "edible and said to make excellent jam" according to notes on one specimen (Donald 2324). NOTES. In Sleumer's (1972) revision Dovyalis keniensis would be placed within sect. Dovyalis which is defined by an ovary with 2 -3 placentas, each placenta bearing 1 ovule and styles 2 -3 (rarely 4). Using Sleumer's (1972) key for the genus, D. keniensis would be in a couplet with D. lucida Sim. and D. mollis. D. keniensis, with sparsely pubescent leaves, is most similar to D. mollis as D. lucida has glabrous, coriaceous leaves. D. mollis is from northwest Angola (Cabinda and Cuanza Norte provinces) and western Democratic Republic of Congo (Mayumbe area) in forest and mixed thickets up to 1300 m (Sleumer 1972). D. mollis and D. keniensis are widely separated geographically and differ by leaf, spine and flower characters (Table 1). However they share some characters, for example, similar fruits (both velvety hairy and orange coloured) and pubescence (laxly hairy leaves and flowers densely yellow tomentose). Genetic studies are suggested to clarify the relationship between D. keniensis and D. mollis.
In Kenya, Dovyalis keniensis has sometimes been mistakenly identified as D. hispidula Willd., also found in forests along the coast. However there are many differences between these two species (Table 1), for example, in leaf shape, colour of hairs on flowers and fruit pubescence. In F.T.E.A. (Sleumer 1975) D. keniensis would key out in the couplet with D. hispidula and D. xanthocarpa Bullock. However D. xanthocarpa is a Tanzanian endemic from forests and bushland at 630 -1370 m., has larger leaves (5 -8 × 2.5 -5 cm) and tepals accrescent in fruit to 12 mm (in D. keniensis tepals are not accrescent and remain 2 -3 mm long in fruit). Four species of Dovyalis are now found in Kenya, D. keniensis, D. hispidula, D. abyssinica (A. Rich.) Warb. and D. macrocalyx (Oliv.) Warb. A new key based on F.T.E.A. is presented below: