Research Article |
Corresponding author: Iain Darbyshire ( i.darbyshire@kew.org ) Academic editor: Yasen Mutafchiev
© 2019 Saba Rokni, Bart Wursten, Iain Darbyshire.
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.
Citation:
Rokni S, Wursten B, Darbyshire I (2019) Synsepalum chimanimani (Sapotaceae), a new species endemic to the southern foothills of the Chimanimani Mountains of Mozambique and Zimbabwe, with notes on the botanical importance of this area. PhytoKeys 133: 115-132. https://doi.org/10.3897/phytokeys.133.38694
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Synsepalum chimanimani S.Rokni & I.Darbysh., sp. nov., a small tree endemic to the forests of the southern foothills of the Chimanimani Mountains of Mozambique and Zimbabwe, is described and illustrated. The differences in morphology and distribution between the new species and the related S. kaessneri and S. muelleri, with which it has been confused, are clarified. The new species is globally Endangered due to ongoing habitat loss within its restricted range. The botanical importance and conservation of the Chimanimani foothills is also discussed, and they are highlighted as a candidate Important Plant Area.
conservation, herbarium, Important Plant Area, Makurupini, taxonomy
Synsepalum (A.DC.) Daniell is a genus of approximately 35 species of evergreen shrubs or trees native to tropical Africa (
In a recent molecular phylogenetic study by
The new species of Synsepalum described here, recorded from the lowland forests of the Chimanimani Mountains on the border of Mozambique and Zimbabwe, has previously been treated as conspecific with S. kaessneri (Engl.) T.D.Penn. (
In their comprehensive guide to the trees and shrubs of Mozambique,
In this paper we describe the Chimanimani taxon as a new species and clarify the differences in morphology and distribution between our new species and S. kaessneri and S. muelleri. We also present a distribution map and list of specimens examined for the three species and discuss the conservation and botanical importance of the Chimanimani foothills.
Specimens of Synsepalum species in the Kew herbarium (K), the British Museum of Natural History (
Thirty qualitative and quantitative characters were examined in specimens of S. kaessneri and the newly described species (see Suppl. material
In the Discussion section the application of Important Plant Areas (IPA) criteria follows
Tulestea kaessneri sensu Aubréville in Adansonia Sér. 2, 12(2): 191–192 (1972), pro parte quoad Wild, Goldsmith & Müller 6645, non (Engl.) Aubrév. sensu stricto.
Afrosersalisia kaessneri sensu Kupicha in Flora Zambesiaca 7(1): 217 (1983), pro parte quoad spec. ex Mozambique & Zimbabwe, non (Engl.) J.H.Hemsl.
Synsepalum kaessneri sensu Pennington in Gen. Sapotac.: 249 (1991), pro parte, non (Engl.) T.D.Penn. sensu stricto.
Synsepalum muelleri sensu Burrows et al. in Trees & Shrubs Mozambique: 744 (2018), pro parte – photographs and reference to distribution in Haroni-Makurupini Forest; non (Kupicha) T.D.Penn.
Synsepalum
sp. aff. S. kaessneri (Engl.) T.D.Penn., Hyde et al. in
MOZAMBIQUE. Manica Province: Magorogodo hills, Zomba Community, 19°54'28"S, 33°11'4"E, c. 559 m alt., fl. and fr. 28 October 2013, B.T. Wursten BW897 (holotype:
This species differs from Synsepalum kaessneri (Engl.) T.D.Penn. in the generally smaller (7.9–12.6 x 1.7–3.4 cm versus 9.8–16.7 x 2.8–5.2 cm) narrowly elliptic leaves with a long and narrow acuminate tip versus oblanceolate leaves with a short and broad acuminate tip (see illustration, Fig.
Synsepalum chimanimani (A-K) and Synsepalum kaessneri (L) A habit B stem apex with apical buds/young leaves and petioles showing indumentum C medifixed hairs on stem D abaxial leaf surface showing sparse medifixed hairs on midrib E leaf showing (faint) secondary veins F flower cluster showing bud, open flower and partially opened flower G flower, side view (hydrated) H corolla after removal of two petals and stamens (hydrated) I stamen and staminodes in situ on petal, inner face bases of neighbouring petals shown J side view of stamen and petal (staminodes omitted) K immature fruit (from photograph) L leaf (abaxial) of Synsepalum kaessneri. A, D-K drawn from B.T. Wursten BW897 (BR0000020700003) B, C from Timberlake et al. 6197 (K001291035) L drawn from Magogo & Glover 280 (K). Scale bars: 1mm (Single bar); 2 mm and 5 mm (graduated single bar); 1 cm (double bar); 5 cm (graduated double bar). Drawn by Andrew Brown, November 2018.
Diagnostic characters for separating Synsepalum chimanimani from Synsepalum kaessneri.
Character | Synsepalum chimanimani | Synsepalum kaessneri |
---|---|---|
Leaf shape | Narrowly elliptic to rarely oblanceolate | Oblanceolate |
Leaf apex | long acuminate, tip narrow, rounded | short acuminate with a broad rounded tip |
Leaf width (mm) | 17–34 | 28–52 |
Leaf length (mm) | 79–126 | 98–167 |
Leaf length: width ratio | 3.1–5.83 | 2.7–4.14 |
Pedicel length (mm) – flowers | Flowers sessile or almost so – pedicel less than 1 mm long | Flowers stalked – pedicel 1–3 mm long |
Pedicel length (mm) – fruit | 2 | 3–5 |
Corolla lobes – shape | Broadly ovate | Ovate |
Corolla lobes length (mm) | 1.45–1.5 | 1.8–1.9 |
Corolla lobes length: width ratio | 1–1.21 | 1.29–1.36 |
Corolla tube length (mm) | 0.75–0.8 | 1.2 |
Corolla – total length (mm) | Less than 2.5 mm | c. 3 mm |
Stamens | Anthers 0.9–1 mm long, thecae elliptic with a minute, inconspicuous point at the apex of the connective | Anthers 1.25 mm long, arrow-head shaped, thecae oblong with conspicuous apiculate apex to connective |
It has previously been confused with Synsepalum muelleri (Kupicha) T.D.Penn. but is easily separated by the very faint secondary venation and no visible tertiary venation versus clearly visible secondary and reticulate tertiary venation; no stipules versus persistent subulate stipules 2–7 mm long; whitish-green flowers with a very short corolla tube and wide-spreading lobes versus white tubular flowers with the tube markedly longer than the lobes; corollas less than 2.5 mm long versus 7–10 mm long; exerted stamens versus included stamens; minute staminodes versus no staminodes; fruit 1–1.3 cm long with a very short (0.5 mm long) style versus larger fruit 2–3 cm long with a 5–7 mm long persistent style; glabrous fruit except for hairs at the tip around the base of the style versus fruit covered with rust-coloured hairs.
Small tree or shrub up to 4 m high. Bark brown and finely fissured. Branching repeatedly subterminal (“Terminalia-style”) with leaves confined to branch apices. Older stems glabrous with finely fissured brownish-grey bark, young shoots, buds and petioles of young leaves with indumentum of appressed, very fine rust-coloured hairs. Hairs medifixed, less than 0.5 mm long, tips sharp. Stipules absent. Leaves with petiole 3–5 mm long, often sparsely hairy to glabrous on older leaves; lamina narrowly elliptic to rarely oblanceolate, 7.9–12.6 x 1.7–3.4 cm, apex long acuminate with a narrow rounded tip, margins entire and repand, base attenuate; midrib raised on both surfaces with striations on the midrib below, lateral veins very faint above, more distinct below, pinnate, curving towards the margin, 9–15 pairs of lateral veins, no visible tertiary venation; both surfaces finely rugose and glabrous except for sparse scattered hairs along the midrib on the lower surface, particularly on younger leaves; hairs very fine, rust-coloured, medifixed, less than 0.5 mm long, tips sharp. Flowers in clusters in leaf axils and along the branches below the leaves, small and whitish-green, sessile or almost so, pedicels less than 1 mm long (extending to 2 mm long in fruit), pedicels and external surface of calyx lobes covered with sub-appressed, medifixed, very fine rust-coloured hairs. Calyx cup-shaped, 5-lobed, lobes nearly free, imbricate, elliptic, 1.2–1.3 x 1–1.1 mm, with hyaline margins, glabrous internally. Corolla 5-merous, fused at base, tube up to 0.8 mm long, lobes involute, broadly ovate, 1.45–1.5 mm long, rounded at apex. Stamens attached at base of petals, filaments 0.6 mm long, anthers 0.9–1 mm long, the two thecae elliptic with a tiny, inconspicuous point at the apex of the connective. Staminodes minute, alternating with the petals and stamens, divided and irregularly shaped. Ovary densely hairy, with a few hairs extending onto the style, ovoid, 1mm long, style 0.5 mm long. Fruit fleshy, red when ripe, solitary, ellipsoid, 10–13 x 6–8 mm (measurements taken from dried material), with calyx and corolla persisting at base and with persistent style at apex, glabrous except for a few hairs at apex around base of style. Seed compressed-ellipsoid, 12 x 7 x 3 mm, glossy brown, with duller elliptic scar c. 5 mm wide extending the length of the seed, cotyledons large, plano-convex, endosperm absent (fide
Known only from lowland, moist forests in the foothills of the southern Chimanimani mountains of Mozambique and Zimbabwe. It has been recorded from three localities: the Haroni-Makurupini Forest in Zimbabwe, and the Maronga forest (Maronga Community) and Thekeza forest (Zomba Community) in Mozambique. It occurs in the understorey of moist evergreen and semi-deciduous forests at an altitude of 305–560 m. In the Maronga Community area at the base of the Chimanimani Mountains, where this species is locally frequent, most of the area is covered by moist evergreen forest. The dominant tree here is Newtonia buchananii (Baker f.) G.C.C.Gilbert & Boutique with Maranthes goetzeniana (Engl.) Prance and Xylopia aethiopica (Dunal) A.Rich. also common. Funtumia africana (Benth.) Stapf forms a high sub-canopy along with Aporrhiza nitida Gilg, Blighia unijugata Baker, Millettia stuhlmannii Taub., Synsepalum brevipes (Baker) T.D.Penn. and Trilepisium madagascariense DC. The understorey is dominated in some areas by Drypetes arguta (Müll. Arg.) Hutch. and other locally abundant shrubs include Rinorea convallarioides (Baker f.) Eyles, Rinorea ferruginea Engl., Tabernaemontana ventricosa Hochst. ex A.DC., Tricalysia pallens Hiern and the rare Vepris drummondii Mendonça. There are also many lianas (
Plants were collected in flower in July (buds) and October (open), and in fruit in October and December. Flowering occurs at the end of the dry season and beginning of the rainy season, the main rainy season in the Chimanimani area being from November to late March or April (
The specific epithet is taken from the Chimanimani mountains to which the species is confined.
Synsepalum chimanimani S.Rokni & I.Darbysh, sp. nov. has been assessed as Endangered under IUCN criterion B (EN B1ab(iii)+2ab(iii);
MOZAMBIQUE. Manica Province: Magorogodo hills, Zomba Community, 19°54.467'S, 33°11.067'E, alt. c. 559 m, fl. and fr. 28 October 2013, Wursten BW897 (
Sersalisia kaessneri Engl., Engler in Mon. Afr. Pflanzen. 8: 31 (1904) (genus queried by original author).
Pouteria kaessneri (Engl.) Baehni, in Candollea 9: 280 (1942) (genus queried by author).
Afrosersalisia kaessneri (Engl.) J.H.Hemsl., Hemsley in Kew Bull. 20: 483 (1966); in F.T.E.A., Sapotaceae: 44 (1968).
Tulestea kaessneri (Engl.) Aubrév., Aubréville in Adansonia Ser. 2, 12(2): 191–192 (1972), pro parte quoad T. Kässner 398.
KENYA. Kwale County: Makoni near Mombasa, fl. 20 March 1902, T. Kässner 398 (B, holotype, destroyed;
KENYA. Kwale County: Makoni near Mombasa, fl. 20 March 1902, Kässner 398 (B, holotype, destroyed;
Moist evergreen and dry semi-deciduous forests. Altitude 300–1100 m.
Flowering September & March. Fruiting January & May.
Vincentella muelleri Kupicha in Candollea 33 (1): 37, fig. 4 (1978); Kupicha in Sapotaceae Flora Zambesiaca 7(1): 228 (1983).
MALAWI. Southern Region: Mulanje District, Ruo Gorge, alt. 900 m, fl. and fr. 1 September 1970, T. Müller 1463 (K!, holotype, K000049396;
MALAWI. Southern Region: Mulanje Mountains, Ruo Gorge at the Savani stream crossing, alt. 1250 m, fr. 30 September 1986, Chapman & Chapman 8104 (K!, K000049398; E!, E00330780; MO); Mulanje Mountains, Litchenya Plateau, along the perimeter fire trace near the crater lip, alt. 1920 m, fr. 12 November 1986, Chapman & Chapman 8209 (K!, K000049399; E!, E00330776; MO); Mulanje Mountains, Chisongeli Forest, Muluzi catchment, alt. 1650 m, fl. 30 September 1988, Chapman & Chapman 9339 (K!, K000049397; E!, E00330775; MO); Mulanje, Ruo Gorge, fl. and fr. 26 August 1983, Dowsett-Lemaire 942 (K!, K000049400;
In the understorey of Newtonia buchananii-dominated moist forest, Garcinia kingaensis Engl. dominated moist forest and dense humid riverine forest at elevations of 900–1920 m.
Flowering August to November. Fruiting August to January. There is a distinct rainy season in Mabu, Namuli, Ribáuè, Chiperone and Mulanje with the main rainfall months being November to April with a dry season from May to October. Flowering occurs at the end of the dry season and beginning of the rainy season with fruiting following.
We have only one flowering specimen of S. chimanimani sp. nov. and it has rarely been collected in fruit. It would be useful to have more flowering specimens for a more thorough comparison with S. kaessneri, which may reveal additional diagnostic characters. However, the two taxa are very clearly separated geographically by nearly 1,500 km and there are sufficient morphological differences for separation at the species level. A molecular phylogenetic study that includes the three taxa in this paper would also be useful to better understand relationships within Synsepalum and between S. chimanimani, and S. kaessneri. and S. muelleri. Whilst the molecular study by
Both S. chimanimani sp. nov. and S. kaessneri are rare species with restricted ranges and of conservation concern because of ongoing threats to the known populations. There are no known ex situ collections of either species (
The high Chimanimani Mountains have long been renowned for their high botanical endemism, particularly associated with the extensive outcrops of nutrient-deficient quartzites (
The area of particular interest stretches from the lower valleys of the Rusitu and Haroni Rivers of Zimbabwe, the Makurupini area on the Zimbabwe-Mozambique border and the Maronga, Zomba and Mpunga communities of Mozambique. The botanical diversity of the Haroni-Rusitu-Makurupini region has been documented in an unpublished checklist of 787 species, compiled from a range of expeditions made between 1955 and 1998 (
The forests vary in species composition and in the relative extent of evergreen versus deciduous components; the species composition in the Mozambican portion of these forests is discussed in detail by
Although of relatively low species richness compared to lowland forests in other parts of tropical Africa, the Chimanimani forests support a number of rare and threatened plant species. For example, the spectacular herb Streptocarpus acicularis I.Darbysh. & Massingue is so far known only from a single collection from along the Mevumozi River near Maronga (
These forests also support species that are nationally rare for Zimbabwe and/or Mozambique, including some interesting outlier populations. For example, Ficus mucuso Welw. ex Ficalho and Raphidiocystis chrysocoma (Schumach.) C.Jeffrey, West African species that are known in the Flora Zambesiaca region only from these forests, and Dianella ensifolia (L.) DC., a species of horticultural importance with an Indian Ocean distribution, on the African continent known in the wild only from the Chimanimani, Mabu and Ribáuè mountains of Mozambique. It is locally frequent at Maronga (
The forests are interspersed with extensive areas of miombo woodland, dominated by Brachystegia (most frequently B. spiciformis Benth.) and Uapaca species. Whilst important ecologically, the miombo does not contain high numbers of rare or threatened plant species. Of greater botanical significance is the presence of three other vegetation types within this mosaic:
1. Low elevation outcrops of nutrient-deficient quartzites, usually associated with light woodland dominated by Brachystegia microphylla Harms. These outcrops are most frequent in the Makurupini-Maronga area but also extend further east. They support an interesting rock flora including the endemic Ficus muelleriana C.C.Berg, a tiny fig that climbs on the rock faces, and Otiophora lanceolata Verdc., a locally abundant endemic shrublet. Aloe ballii Reynolds, including its two varieties var. ballii and var. makurupiniensis Ellert (both Vulnerable), is a delicate grass aloe restricted to quartzite slopes along the Zimbabwe-Mozambique border. Other range-restricted and/or scarce species of this habitat include Sclerochiton coeruleus (Lindau) S.Moore, Gutenbergia westii (Wild) Wild & G.V.Pope and Sericanthe chimanimaniensis Wursten & de Block ined. (see
2. Seasonally wet grasslands, which occur in small scattered areas within the forest-woodland mosaic. These support an interesting, though not diverse, herb flora including the recently resurrected species Crepidorhopalon flavus (S.Moore) I.Darbysh. & Eb.Fisch. whose range is centred on the southern Chimanimani foothills (
3. Swamps and lowland watercourses that are fringed by large stands of the striking tree Pandanus livingstonianus Rendle. Whilst fairly widespread, this tree has very isolated and localised populations and is thought to be threatened by habitat loss (
The entirety of this area falls within the Chimanimani Trans-Frontier Conservation Area (TFCA), in part within the core TFCA, i.e. the Chimanimani National Park of Zimbabwe and Chimanimani National Reserve of Mozambique, and in part within the TFCA buffer zone. This buffer zone includes the Maronga, Zomba and Moribane Forest Reserves in Mozambique (see
Applying the Important Plant Areas (IPA) criteria as revised by
Taxa that qualify the Chimanimani foothills as an Important Plant Area under criterion A: threatened species.
Family | Taxon | IUCN Red List assessment | IPA sub-criteria met | Notes |
Asphodelaceae | Aloe ballii Reynolds | VU D2 | A(i) | Two varieties, var. ballii and var. makurupiniensis |
Asteraceae | Gutenbergia westii (Wild) Wild & G.V.Pope | VU B1ab(iii)+2ab(iii) | A(i) | |
Commelinaceae | Cyanotis chimanimaniensis Faden ined. | Not Evaluated | A(iv) | Species currently under description |
Fabaceae | Tephrosia longipes var. swynnertonii (Baker f.) Brummitt | Not Evaluated | A(iv) | |
Gesneriaceae | Streptocarpus acicularis I.Darbysh. & Massingue | CR B2ab(iii) | A(i) | |
Linderniaceae | Crepidorhopalon flavus (S.Moore) I.Darbysh. & Eb.Fisch. | Not Evaluated | A(iv) | Provisionally assessed as Vulnerable – VU B1ab(iii) – by |
Loranthaceae | Englerina swynnertonii (Sprague) Polhill & Wiens | Not Evaluated | A(iii) | |
Moraceae | Ficus muelleriana C.C.Berg | EN B1ab(iii)+2ab(iii) | A(i) | |
Phyllanthaceae | Phyllanthus bernierianus var. glaber Radcl.-Sm. | Not Evaluated | A(iv) | |
Poaceae | Danthoniopsis chimanimaniensis (J.B.Phipps) Clayton | EN B1ab(iii)+2ab(iii) | A(i) | |
Rubiaceae | Afrocanthium ngonii (Bridson) Lantz | VU B1ab(iii)+2ab(iii)* | A(i) | |
Coffea salvatrix Swynn. & Phillipson | EN B2ab(i,ii,iii) | A(i) | ||
Otiophora lanceolata Verdc. | VU B1ab(iii)+2ab(iii) | A(i) | ||
Sericanthe chimanimaniensis Wursten & De Block ined. | VU B1ab(iii)+2ab(iii)* | A(i) | Species currently under description | |
Rutaceae | Vepris drummondii Mendonça | VU B1ab(iii)+2ab(iii) | A(i) | |
Sapotaceae | Synsepalum chimanimani S.Rokni & I.Darbysh. | EN B1ab(iii)+2ab(iii) | A(i) | |
Zamiaceae | Encephalartos chimanimaniensis R.A.Dyer & I.Verd. | EN B1ab(i,ii,iv,v)+ 2ab(i,ii,iv,v); C1 | A(i) – see note | Requires confirmation that this species is still extant within proposed IPA |
Fieldwork conducted in the foothills of the Chimanimani Mountains in 2015 was sponsored by the Darwin Initiative award 2380: “Balancing Conservation and Livelihoods in the Chimanimani Forest Belt, Mozambique” completed in 2017. We thank Andrew Brown for the illustration of the new species. We thank Ranee Prakesh (
Examined characters of S. kaessneri and the newly described species
Data type: species data