Taxonomy of Atlantic Central African orchids 5. A new species of Angraecum sect. Conchoglossum (Orchidaceae, Angraecinae) from Gabon and Cameroon

Abstract

Recent field inventories and taxonomic research in Central Africa have resulted in the discovery of many new orchid species. Five specimens of an apparently new Angraecum species were collected in Gabon and Cameroon. They stand out for their hanging habit and short zig-zag stem. Morphology of leaves and habit is somewhat comparable to A. cultriforme and A. stolzii, two species from East Africa. Flowers of the novelty share the general morphology of A. pyriforme from which the new species is distinguished by being smaller and with a different lip-spur ratio. Here we show that these five specimens represent a new species, described here as Angraecum lanceolatum. The distinguishing traits include thin lanceolate leaves, convolute distally, with a rhombic lip shape. Dichotomous key to four Central African species of sect. Conchoglossum and a table of the diagnostic characters of the seven related Continental African Angraecum taxa are included here. A preliminary assessment of the conservation status of A. lanceolatum is provided, using the IUCN Red List Categories and Criteria.

Full text

A new Angraecum species from Gabon and Cameroon 61
Taxonomy of Atlantic Central African orchids 5.
A new species of Angraecum sect. Conchoglossum
(Orchidaceae, Angraecinae) from Gabon
and Cameroon
Vladimir Ječmenica1,2, Vincent Droissart2,3,4,5, Nausicaa Noret1, Tariq Stévart2,4,6
1 Laboratoire d’Écologie végétale et Biogéochimie, CP 244, Université Libre de Bruxelles, Boulevard du Triomphe,
B-1050 Brussels, Belgium 2 Herbarium et Bibliothèque de Botanique africaine, CP 265, Université Libre de
Bruxelles, Boulevard du Triomphe, B-1050 Brussels, Belgium 3 Institut de Recherche pour le Développement
(IRD), Unité Mixte de Recherche AMAP (Botanique et Bioinformatique de l’Architecture des Plantes), Boulevard
de la Lironde, TA A-51/PS2, F-34398 Montpellier Cedex 5, France 4 Missouri Botanical Garden (MBG),
Africa & Madagascar Department, P.O. Box 299, St. Louis, Missouri 63166-0299, U.S.A. 5 Plant Systematic
and Ecology Laboratory, Higher Teacher’s Training College, University of Yaoundé I, Yaoundé, Cameroon
6 Botanic Garden, Meise, Domein van Bouchout, Nieuwelaan 38, B-1860 Meise, Belgium
Corresponding authors: Vladimir Ječmenica (jvlada_90@yahoo.com); Tariq Stévart (tariq.stevart@mobot.org)
Academic editor: L. Peruzzi|Received 30 October 2015|Accepted 27 December 2015|Published 25 February2016
Citation: Ječmenica V, Droissart V, Noret N, Stévart T (2016) Taxonomy of Atlantic Central African orchids 5. A new
species of Angraecum sect. Conchoglossum (Orchidaceae, Angraecinae) from Gabon and Cameroon. PhytoKeys 61: 61–71.
doi: 10.3897/phytokeys.61.7017
Abstract
Recent eld inventories and taxonomic research in Central Africa have resulted in the discovery of many
new orchid species. Five specimens of an apparently new Angraecum species were collected in Gabon and
Cameroon. ey stand out for their hanging habit and short zig-zag stem. Morphology of leaves and
habit is somewhat comparable to A. cultriforme and A. stolzii, two species from East Africa. Flowers of
the novelty share the general morphology of A. pyriforme from which the new species is distinguished by
being smaller and with a dierent lip-spur ratio. Here we show that these ve specimens represent a new
species, described here as Angraecum lanceolatum. e distinguishing traits include thin lanceolate leaves,
convolute distally, with a rhombic lip shape. Dichotomous key to four Central African species of sect.
Conchoglossum and a table of the diagnostic characters of the seven related Continental African Angraecum
taxa are included here. A preliminary assessment of the conservation status of A. lanceolatum is provided,
using the IUCN Red List Categories and Criteria.
PhytoKeys 61: 61–71 (2016)
doi: 10.3897/phytokeys.61.7017
http://phytokeys.pensoft.net
Copyright Vladimir Ječmenica et al. 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.
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Vladimir Ječmenica et al. / PhytoKeys 61: 61–71 (2016)
62
Résumé
Des travaux récents d’inventaires et de taxonomie ont abouti à la découverte de nombreuses espèces nou-
velles d’orchidées en Afrique centrale. Cinq spécimens n’appartenant à aucune espèce d’Angraecum connue
à ce jour ont été récoltés au Gabon et au Cameroun. Ces spécimens se distinguent par un port pendant et
une tige courte disposée en zigzag. Leur morphologie foliaire et leur port sont proches de ceuxd’A. cultri-
forme et d’A. stolzii, deux espèces d’Afrique de l’Est. Les eurs de cette nouveauté taxonomique présentent
la morphologie générale d’A. piriforme, mais sont cependant plus petites et présentent un rapport diérent
de la longueur du labelle sur celle de l’éperon. Nous montrons ici que ces cinq échantillons représentent une
nouvelle espèce, décrite sous le nom d’Angraecum lanceolatum. Les traits distinctifs de ce nouveau taxonsont
ses feuilles minces, lancéolées et tordues à l’apex, ainsi que la forme du labelle en losange. Une clé dichoto-
mique des quatre espèces de la section Conchoglossum présentes en Afrique centrale et une table des carac-
tères diagnostiques des six taxons proches d’A. lanceolatum présents en Afrique continentale sont proposées.
Le statut de conservation d’A. lanceolatum est évalué selon la méthodologie de la Liste Rouge de l’UICN.
Keywords
Angraecoid, Campo-Ma’an National Park, Ivindo National Park, Monts de Cristal National Park, IUCN
Red List Categories and Criteria
Introduction
According to the latest count of WCSP (Govaerts et al. 2015), the genus Angraecum
Bory comprises 223 species. With 173 species recorded in the Malagasy region (Go-
vaerts et al. 2015), Madagascar and the Mascarenes are considered as the centre of
diversity of Angraecum. Nevertheless, Central Africa also shows a high orchid diversity
and endemism rate (Stévart 2003, Droissart 2009) where many new species remain
to be described. A cultivation system established in São Tomé, Gabon, Equatorial
Guinea and Cameroon by Stévart (2003) and his collaborators has allowed collection
of thousands of owering specimens. is has enabled taxonomic revisions of several
orchid genera (Verlynde et al. 2013, Simo-Droissart et al. 2014) and the description of
more than 25 new orchid taxa (e.g. Droissart et al. 2014, Stévart et al. 2014, D’Haijere
et al. 2015), many of which still remain to be published.
A revision of Angraecum species belonging to sections Afrangraecum Summerh.
and Conchoglossum Schltr. was conducted by the rst author in 2015. A careful exami-
nation of specimens from main herbaria has conrmed the status of ve new species,
of which one is described here.
e rst collection of the new species originates from Mont Seni in the Monts de
Cristal National Park in Gabon (IUCN Category II National Park). is specimen
was collected by Nguema Miyono (N. Miyono 2037) in 2001 and deposited in BRLU
and LBV (abbreviations after iers continuously updated). Unfortunately, the mate-
rial was sterile and identied as Angraecum angustipetalum Rendle. A few years later,
during eldwork in the Ivindo National Park in Gabon, a living plant of the same
species was collected by Diosdado Nguema. e specimen was sent to the garden of

A new Angraecum species from Gabon and Cameroon 63
M. Biteau (Jardi-Gab, Libreville) who cultivated it in his shade-house under number
BTO23. Since then, the plant has produced three owering specimens (D. Nguema
s.n., JBB 244 and JBB 263) after which it died. Following examination of the three
owering specimens and the living plant (BTO23), Stévart considered it as a poten-
tially new species. Finally, eldwork conducted in Cameroon by Droissart in February
2015 enabled another collection of that new species (Droissart et al. 1874). e speci-
men was collected in the Campo-Ma’an National Park (South Region of Cameroon)
and cultivated in Yaoundé shade-house under number Y 5652 NY where it owered
in June 2015. Comparison of these ve specimens with the type material of related
Angraecum species conrmed that these specimens represent a new species, described
here as Angraecum lanceolatum.
is paper is the fth in a series of publications (Stévart et al. 2010, Droissart et
al. 2014, Stévart et al. 2014, D’Haijere et al. 2015) based on recent intensive eld-
work and focusing on collections-based taxonomic revisions of Orchidaceae in Atlan-
tic Central Africa.
Material and methods
is study was conducted under the framework of the rst author’s Master’s thesis.
A revision including 109 specimens from all Angraecum species belonging to sec-
tions Afrangraecum and Conchoglossum was undertaken. Collections of BR, BRLU,
K, WAG, MA, MO, P and YA were examined and did not reveal any additional
specimens of the new species. Description of the new species is based on ve spirit
preserved specimens originating from Gabon and Cameroon. e terminology used
for description followed Systematics Association Committee for Descriptive Biologi-
cal Terminology (1962a, 1962b), Botanical Latin (Stearn 1992) and e Kew Plant
Glossary (Beentje 2010). Two living specimens of the new species were collected by
teams of the Missouri Botanical Garden (MBG) and the Institut de Recherche pour
le Développement (IRD) during eldwork in Gabon and Cameroon. Sterile mate-
rial collected in the eld was grown in the shade-houses until obtaining owered
specimens preserved as spirit collections. Colour and habit characteristics given are
based on the eld data and high resolution photographs. Additional photographs,
measurements and morphological study of spirit material were carried out using an
optic microscope Zeiss STEMI SV11.
A preliminary risk of extinction assessment was made using the IUCN Red List
Categories and Criteria (IUCN 2001, 2014). Georeferenced specimen data were
imported into GIS to calculate area of occupancy (AOO) and extent of occurrence
(EOO). e cell size for AOO was set 2 × 2 km as recommended by IUCN (2014).
Each locality was regarded as a separate subpopulation. e number of ‘locations’ (as
dened by IUCN 2014) was calculated with regard to the kind of threats, such that a
single ‘location’ may encompass more than one adjacent population.

Vladimir Ječmenica et al. / PhytoKeys 61: 61–71 (2016)
64
Taxonomic treatment
Angraecum lanceolatum Ječmenica, Stévart & Droissart, sp. nov.
urn:lsid:ipni.org:names:77153391-1
Figs 1, 2
Diagnosis. Angraecum lanceolatum is close to A. stolzii Schltr. (1915) but diers from
it by shorter narrowly ovate leaves that convolute in the distal half, by a shorter zig-zag
stem and by a rhombic lip shape. e species also resembles A. cultriforme Summerh.
(1958) but diers from it by smaller ower size and slightly curved spur. Angraecum
lanceolatum is also close to A. pyriforme Summerh. (1936) in the shape of oral parts,
but diers from it by previously stated vegetative characters, hanging habit, single-
owered inorescence and smaller ower.
Type. Cameroon. South Region of Cameroon, Campo-Ma’an National Park, near-
by villages of Ebianemeyong and Nyabissan, 02°29.2488'N, 010°19.9026'E, 14 Feb
2015, V. Droissart, T. Couvreur & N. Kamdem 1874 (holotype: BRLU!; isotype: YA!).
Description. Small epiphytic herbaceous plant. Stem hanging, slightly zig-zag in
form, unbranched, up to 8.5 cm long. Leaves alternate, spaced, narrowly ovate to
lanceolate, sometimes slightly falcate and always convolute in the distal part, margins
entire; distinct midvein forming slight channel, accompanied with 2 or 3 nerves on
each side merging into one throughout; small stomata spots visible in young leaves;
leaf apex unequally bilobed, acuminate, with the larger lobe 1.5–2.8 mm long and the
smaller 0.3–1.2 mm long, leaf blade 2.3–4.1 × 0.6–0.9 cm; leaf internode about 5–6
mm long. Inorescence single owered, eventually two-owered; peduncle elongated
13–23 mm long, opposite to the leaf at the node. Bracts acute, 2 mm long. Flowers
white, opening diameter about 12.5 mm. Ovary and pedicel not resupinate, 8 mm
long. Dorsal sepal 6.2–8.5 × 3 mm, elliptic, acute, thick, with entire margins. Lateral
sepals 6–7 × 2–2.2 mm, elliptic, acute, thick, with entire margins. Petals 5–6.5 × 2–2.2
mm, obliquely elliptic, acute, entire margins, similar in shape to lateral sepals. Lip 5–6
× 4.5–5 mm, concave, rhombic when attened, widest between rst third and the half,
acute; spur 16–19.5 mm, cylindric, slender, straight, somewhat elliptically inated and
greenish at the apex. Column 1.5 × 2 mm. Pollinia 2, pyriforme. Fruit capsule, 18–24
× 3.5–5 mm.
Additional specimens. Gabon. Monts de Cristal National Park. Mont Seni, 13
Sept 2001, Nguema Miyono 2037 (LBV, BRLU!); Ivindo National Park, near Langoué
Bai, 17 Sept 2005, D. Nguema s.n. (BRLU!); ibid., J.P. Biteau 263 (BRLU!); ibid., J.P.
Biteau 244 (BRLU!).
Distribution and habitat. Endemic to the Lower Guinea Domain (Cameroon
and Gabon, Fig. 3). e specimen collected in Cameroon was found at 850 m el-
evation in submontane forest with Gilbertiodendron unijugum (Pellegr.) J. Léonard
(Fabaceae). e plant was epiphyte at about 1.5 m from the ground, on the trunk of a
shrub with a diameter less than 10 cm.
Phenology. Flowering occurs in June and September.

A new Angraecum species from Gabon and Cameroon 65
Figure 1. Photographs of living specimen of Angraecum lanceolatum (A, C, D V. Droissart et al. 1874
BJ.P. Biteau 263): A habit and top view of the ower B half front view of the ower (from spirit material)
C inorescence and ower D habit and peduncle with fruit. Photographs taken by: A, D V. Droissart;
B V. Ječmenica; C G. Kamdem.
Conservation. IUCN Red List category: Least Concern [LC]. e extent of oc-
currence (EOO) of Angraecum lanceolatum is estimated to be over 23,884 km2, ex-
ceeding the 20,000 km2 upper limit for Vulnerable status under the criterion B1,
whereas its area of occupancy (AOO) is estimated to be 12 km2 (which falls within the
limits for Endangered status under the criterion B2). e species is now known from
three subpopulations in Gabon and Cameroon. ese three subpopulations represent
three dierent locations (sensu IUCN 2014), less than ve locations, which is the up-

Vladimir Ječmenica et al. / PhytoKeys 61: 61–71 (2016)
66
Figure 2. Angraecum lanceolatum: A Sepals B Petal C Lip, column, ovary and pedicel, spur D Lip,
attened, overhead view E Column without anther cap F Anther cap G Pollinia. Bars represent 1 mm.
Illustration of specimen D. Nguema s.n. by Danka Ječmenica and Vladimir Ječmenica.
per limit for Endangered status under the subcriterion ‘a’ of criterion B2. Angraecum
lanceolatum has only been collected in protected areas (Monts de Cristal and Ivindo
National Parks in Gabon and Campo-Ma’an National Park in Cameroon). None of

A new Angraecum species from Gabon and Cameroon 67
these protected areas is under threat and they appear well managed. Angraecum lan-
ceolatum is thus not threatened. e available information suggests that the number
of subpopulations and mature individuals, as well as its EOO and AOO, will not
decrease noticeably in 10 years or 3 generations the future. Application of the IUCN
criteria therefore indicates that it cannot be regarded as Endangered despite the fact
that its AOO is limited. Angraecum lanceolatum is therefore assigned a preliminary
status of LC.
Etymology. e specic epithet of the new species owes to the particular leaf
shape. Even though there are several interpretations of “lanceolate” shape according to
dierent authors (Linnaeus, Lindley), we relied on the current depiction from Beentje
(2010) that describes it as narrowly ovate and tapering to a point at the apex.
Figure 3. Distribution of Angraecum lanceolatum in tropical Africa.

Vladimir Ječmenica et al. / PhytoKeys 61: 61–71 (2016)
68
Table 1. Morphological comparison of characters for seven related continental African Angraecum species. All species belong to section Conchoglossum except for A.
pyriforme, which is a member of section Afrangraecum. Diagnostic characters are indicated in bold.
Taxa Distribution Stem size Leaves Peduncle Sepals Petals Lip Spur
Angraecum
stolzii Schltr.
Democratic Republic of the
Congo, Tanzania, Malawi,
Zambia
15.5–40 cm
5.6–8 × 0.5–0.9
cm linearly falcate,
acuminate apex
1.3–2.2 cm
Elliptic, acuminate,
lateral falcate,
4–7.3 mm × 1.8
mm
Elliptic,
acuminate,
3–6.2 × 1.3 mm
Ovate, acute,
3–5.5 × 2–2.5
mm
Straight or slightly
curved, elliptic
apical ination, 2.5–
4.6mmlong
Angraecum
egertonii
Schltr.
Nigeria, Cameroon, Gabon 10–22cm 2.7–4 × 1.5–1.9 cm
ovate, acute apex 2–4 cm
Elliptic, acute,
lateral sometimes
falcate, 8–12.8 ×
2–4 mm
Elliptic to
falcate, acute,
7.5–11.5 ×
1.5–2.5 mm
Elliptic to
ovate, acute,
7–11 × 2.5–
4.5mm
Bent upwards with
circular apical
ination, 6.5–8.5 mm
long
Angraecum
pyriforme
Summerh.
Ivory Coast, Nigeria 8–11 cm
7–11 × 1–2.2
cm narrowly
elliptic, obliquely
roundapex
2–4 cm Elliptic, acute,
7–11 × 2.5–4 mm
Obliquely
elliptic, acute,
6.5–8.5 ×
1.5–4mm
Rhombic,
acuminate,
6–7.5 ×
4–4.5mm
Straight with elliptic
apical ination, 10.5–
15mm long
Angraecum
lisowskianum
Szlach. &
Olsz.
Nigeria, Cameroon, Equatorial
Guinea 7.5–11 cm
1.7–2.65 ×
0.7–1.1 cm elliptic,
subacute apex
0.7–1.8 cm
Elliptic, acute,
lateral subfalcate,
6–10.5 × 1.5–3 mm
Elliptic, acute
7.5–9.5 × 1–2.2
mm
Elliptic
to ovate,
acuminate
6.5–8.5 × 4
mm
Straight with elliptic
apical ination, 15–21.5
mm long
Angraecum
cultriforme
Summerh.
Kenya, Tanzania, Malawi,
Mozambic, Zambia, Zimbabwe,
KwaZulu-Natal
8–15 cm
3.7–6 × 0.4–0.8 cm
elliptic to linearly
falcate, acute apex
1.5–3 cm
Elliptic, acuminate,
12.5–18 × 2.3–3
mm
Elliptic,
acuminate,
11–15 × 2–2.5
mm
Ovate,
acuminate,
10–14 × 6 mm
Straight, slightly
ascending with elliptic
apical ination, 20–26
mm long
Angraecum
lanceolatum Cameroon, Gabon Up to 8.5 cm
2.3–4.1 × 0.6–0.9 cm
narrowly ovate to
lanceolate, acuminate
apex
1.3–2.3 cm Elliptic, acute,
6–8.5 × 2–3 mm
Obliquely
elliptic, acute,
5–6.5 × 2–2.2
mm
Rhombic,
acute, 5–6 ×
4.5–5 mm
Irregularly straight with
elliptic apical ination,
16–19.5 mm
Angraecum
moandense De
Wild.
Ghana, Republic of Guinea,
Ivory Coast, Liberia, Nigeria,
Togo, Central African Republic,
Cameroon, Republic of the
Congo, Gabon, Gulf of Guinea
Islands, Rwanda, Democratic
Republic of the Congo,
Tanzania, Uganda
6–15 cm 4.2–9.2 × 0.7–1 cm
oblong, round apex 0.6–3.5 cm Elliptic, acuminate,
8–15.5 × 2–3.5 mm
Obliquely
linear to elliptic,
acuminate,
8–14 ×
1–2.5mm
Elliptic to
slightly ovate,
acuminate
to cuspidate,
8–11.5 ×
2.5–3.5 mm
S-shaped with
occasionally slightly
cylindrically inated
apex, 14–26 mm long

A new Angraecum species from Gabon and Cameroon 69
Taxonomic key to section Conchoglossum species from Central Africa
1a Leaves oblong; spur sigmoid, apex not or rarely slightly cylindrically inated ...
...................................................................................................A. moandense
1b Leaves not oblong; spur straight or slightly curved, apex inated ................ 2
2a Leaves broadly ovate; spur apex circularly inated ...................... A. egertonii
2b Leaves narrowly ovate, lanceolate or elliptic; spur elliptically inated .......... 3
3a Leaves very eshy, broadly elliptic, up to 2.7 cm long; lip elliptic to ovate ....
.......................................................................................... A. lisowskianum
3b Leaves thin, narrowly ovate to lanceolate, distally convolute up to 4.1 cm
long; lip rhombic ..................................................................A. lanceolatum
Notes
e diagnostic characters of species from Central African region that belong to the sec-
tion Conchoglossum, as well as one morphologically related species of the section Afran-
graecum are summarized (Table 1). Morphometric results of the mentioned Master’s
thesis and molecular data on Angraecum (Stévart unpublished) conrmed the status of
the new species. Vegetative morphology and habit of the new species resemble Angrae-
cum stolzii Schltr. in having single owered inorescence and sometimes slightly falcate
leaves. Large and small leaf apex lobes are not prominent as in A. stolzii, in which the
larger lobe reaches at least 10 mm, comparing to a maximum of 2.5 mm in A. lanceola-
tum. Spur is similar in shape but in the new species it is at least three times longer than
the lip, while the ower in A. stolzii has approximately equal spur and lip lengths.
Floral morphology, particularly the lip shape of new species is similar to A. pyri-
forme Summerh. from the sect. Afrangraecum. Nevertheless, ratio between lip and spur
lengths is close to 1:3 in the new species compared to 1:2 in A. pyriforme. Additionally,
the new species has a distinctive habit.
e novelty is a representative of Conchoglossum section according to Stewart et al.
(2006, see also Summerhayes 1958, Angraecoides sensu Garay 1973), due to its conti-
nental distribution and its white single owered inorescence.
Acknowledgments
We express our gratitude to the curators of several herbaria (BR, BRLU, K, L, LBV,
MA, MO, P and YA) for making available their collections and for facilities kindly pro-
vided to the authors. We would like to thank Jean-Philippe Biteau, Gyslène Kamdem
and Sandrine Mayogo for collecting specimens from living material in Libreville and
Yaoundé shade-houses, and Diosdado Nguema for collecting the living plant in the
Ivindo National Park in Gabon.We express our sincere gratitude to Dr Nestor Engone
Obiang, Head of the National Herbarium of Gabon, to Prof. Henry Bourobou, Head

Vladimir Ječmenica et al. / PhytoKeys 61: 61–71 (2016)
70
of IPHAMETRA (CENAREST), to Jean-Philippe Biteau (Jardi-Gab), to Prof. Bon-
aventure Sonké, Head of Plant Systematics and Ecology Laboratory (University of Ya-
oundé I), and to Benjamin Sock, conservator of Campo Ma’an National Park, for the
facilities oered to the authors. We would like to thank the Agence Nationale des Parcs
Nationaux du Gabon (ANPN) and Ministry of Forests and Wildlife in Cameroon
(MINFOF) for allowing us to work in the Ivindo and Campo Ma’an National Parks,
respectively. Fieldwork in Gabon was undertaken under the Memory of Understanding
between the Centre National de la Recherche Scientique et Technologique (CENAR-
EST) and the Missouri Botanical Garden (MBG). Fieldwork, laboratory activities and
herbarium visits were supported by the U. S. National Science Foundation (1051547,
T. Stévart as PI, G. M. Plunkett as Co-PI).
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