Webbia
Journal of Plant Taxonomy and Geography
ISSN: 0083-7792 (Print) 2169-4060 (Online) Journal homepage: http://www.tandfonline.com/loi/tweb20
An update to the African palms (Arecaceae)
floristic and taxonomic knowledge, with emphasis
on the West African region
Fred W. Stauffer, Doudjo N. Ouattara, Didier Roguet, Simona da Giau, Loïc
Michon, Adama Bakayoko & Patrick Ekpe
To cite this article: Fred W. Stauffer, Doudjo N. Ouattara, Didier Roguet, Simona da Giau, Loïc
Michon, Adama Bakayoko & Patrick Ekpe (2017): An update to the African palms (Arecaceae)
floristic and taxonomic knowledge, with emphasis on the West African region, Webbia
To link to this article: http://dx.doi.org/10.1080/00837792.2017.1313381
Published online: 27 Apr 2017.
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Date: 27 April 2017, At: 06:09
Webbia: Journal of Plant taxonomy and GeoGraPhy, 2017
https://doi.org/10.1080/00837792.2017.1313381
An update to the African palms (Arecaceae) floristic and taxonomic knowledge,
with emphasis on the West African region
Fred W. Stauffera, Doudjo N. Ouattarab,c, Didier Rogueta, Simona da Giaua, Loïc Michona, Adama Bakayokob,c
and Patrick Ekped
a
laboratoire de systématique végétale et biodiversité, Conservatoire et Jardin botaniques de la Ville de Genève, Genève, Switzerland; bufr
des Sciences de la nature (Sn), université nangui abrogoua, abidjan, ivory Coast; cdirection de recherche et développement (drd), Centre
Suisse de recherches Scientifiques en Côte d’ivoire, abidjan, ivory Coast; ddepartment of botany, College of basic & applied Sciences,
university of Ghana, legon, Ghana
ABSTRACT
ARTICLE HISTORY
The present contribution is the product of palm research on continental African taxa started
7 years ago and represents an update to our taxonomic and floristic knowledge. Current estimates
indicate that this palm flora is represented by 68 species, grouped in 18 genera attributed to
three subfamilies (Calamoideae, Coryphoideaea and Arecoideae). Although much less species
rich when compared with other palm floras, African palms are extremely interesting from
different perspectives, including phylogenetics, economic botany, ecology and conservation,
all of them briefly discussed in this paper. A historical background on palm studies in Africa is
provided, whereas current efforts on our multi-disciplinary research efforts in West Africa and
future perspectives are depicted.
received 15 march 2017
accepted 19 april 2017
1. Introduction
Continental African palms, in particular the ones native
to the 17 countries of the western region, are currently
the subject of research in the Conservatory and Botanic
Gardens of Geneva. The most accurate estimates for
the continent indicate that the region hosts 68 species,
grouped in 18 genera and attributed to three subfamilies (Calamoideae, Coryphoideaea and Arecoideae)
of the five currently circumscribing the family. Taking
into account generic and specific taxonomic richness,
the native palm flora in this continent is regarded as
much less important when compared with other large
regions or continents of the world: Pacific: 30 gen./128
spp., America: 66 gen./750 spp., Europe: 2 gen./2 spp.,
mainland Asia: 43 gen./354 spp., western Indian Ocean,
including Madagascar : 25 gen./193 spp., Malesia: 50
gen./992 spp. and Oceania (Australia): 21 gen./57 spp.
(data based on Dransfield 1988, 2008; Henderson et al.
1995; Pintaud et al. 2008; Henderson 2009; Stauffer et al.
2014; Govaerts et al. 2017). The low taxonomic richness
reported for the African palm flora is clearly in contrast
to the high economic and ecological importance and
their accurate inventory is critical for their conservation
and sustainable use.
In spite of their recognized importance, many taxa
remain incompletely known and/or only fragmentarily
sampled. Historical collectors visiting Africa, especially
CONTACT fred W. Stauffer
fred.stauffer@ville-ge.ch
© 2017 dipartimento di biologia, università di firenze
KEYWORDS
africa; arecaceae;
conservation; ecology;
ethnobotany; floristics;
taxonomy
those during the eighteenth century (i.e. Palisot de
Beauvois, Thoning, Gardner) (Figure 1), and others
visiting the continent from the early to the mid nineteenth century in the frame of the inventory of biological resources of European colonies (i.e. Chevalier,
Gossweiler, Welwitsch, Zimmerman), gathered palm
specimens from several regions. The European explorers
were not only astonished by the impressive morphology
or growth form displayed by some palm species but also
amazed about the wide range of uses that locals attributed to the different palms. The specimens shipped to
European institutions often had notes on the common
names and the different uses that the local ethnic groups
made of almost all organs of the palms. Once in Europe
those specimens were described by renowned palm
botanists such as O. Beccari, O. Drude, N. von Jacquin,
G. Man, C. von Martius and H. Wendland (Figure 2),
among others.
Unfortunately, a modern taxonomic interpretation of
the palms gathered by means of the study of the original type material represents in many cases a very frustrating task. Many type specimens are no longer extant
(i.e. due to bombing during World War II) or when
present they are fragmentary and poorly informative.
Other complete and more informative type material has
ended up in carpological collections given their bulky
nature. Unfortunately, with some exceptions (Figure 3)
2
F. W. STAUFFER ET AL.
Figure 1. holotype specimen of Raphia vinifera P. beauv. deposited in the herbarium of the Conservatory and botanical Gardens of
Geneva (G) [G00301631]. this specimen was collected by the french explorer Palisot de beauvois during the late eighteenth century
in present-day nigeria–benin.
the collections of bulky specimens in worldwide herbaria
are much less curated than traditional flat specimens and
access to them is strongly hindered if not impossible for
the palm researchers.
Modern standards of palm collecting were applied
by most botanists during the twentieth century. Indeed,
good examples of palm collecting can be identified when
studying the specimens gathered by P. B. Tomlinson
(palms from Ghana), J. P. Profizi (palms from West
Africa), E. de Wildeman (palms from Central Africa), J.
Dransfield (palms from East Africa), C. Jonkind (palms
from West Africa), T. Sunderland (African rattans), J.
van Valkenburg and T. Couvreur (palms from Cameroon
and Gabon), among others. Good quality collections are,
in the case of the palm family, of particular importance
for an accurate taxonomic identification and this is only
possible when extensive field work is associated with
a proper sampling of the specimens (Figure 4). All in
all, the interpretation of available specimens has played
a major role for the publication of monographic treatments for the family. In the case of African palms these
efforts include the publications of Dransfield (1986) on
the palms of East Africa, or more taxonomically oriented
monographs (i.e. Furtado 1967: Hyphaene; Otedoh 1982:
Raphia; Barrow 1998: Phoenix; Bayton 2007: Borassus;
Van Valkenburg and Sunderland 2008; Van Valkenburg
et al. 2007, 2008: Podococcus and Sclerosperma; and
Sunderland 2007, 2012: the African rattan genera
WEBBIA: JOURNAL OF PLANT TAXONOMY AND GEOGRAPHY
Figure 2. Some of the most prominent authors describing the
taxonomic diversity of african palm taxa. (A) Carl von martius,
photo courtesy of botanische Staatssammlung münchen. (B)
hermann Wendland, photo courtesy of landeshauptstadt
hannover, fachbereich herrenhäuser Gärten. (C) odorardo
beccari, photo courtesy of riccardo baldini (florence
herbarium). (D) Caetano xavier furtado.
Calamus, Eremospatha, Laccosperma and Oncocalamus).
The only continental publication effort is restricted to
the book of Tuley (1995) and some taxonomic updates,
including short descriptions of the genera and species
3
and distribution maps, were proposed in the publication
of Stauffer et al. (2014).
The fossil history of the continental African palm
flora, in particular the complex factors explaining its
dramatic decline and its present-day low diversity, has
been the subject of several studies. According to Pan
et al. (2006) the earliest purported African palms are
Aptian [125–112 million years ago (Mya)], with the
particular example of Hyphaeneocarpon aegyptiacum.
The same author has also explained that Tropical West
Africa has been sampled most consistently as a result
from pollen from drill cores (Late Cretaceous–Early
Miocene) whereas East Africa is relatively well sampled
for macrofossils (mostly Neogene). A first decline in the
African palm flora is associated with the Cretaceous–
Palaeogene global extinction event (65 Mya), in which
the disappearance of 47% of palm pollen species was
recorded among fossil genera in West Africa. A second
decline revealing extinctions and appearances at or near
the Eocene–Oligocene boundary indicates a significant
change in the African flora. At least six palm pollen genera disappeared from the African fossil record between
36 and 34 Mya.
Classical authors (i.e. Moore 1973) argued that the
late Quaternary climate shifts could be identified among
the major causes explaining the low species-level richness observed in African palms; however, as indicated
before, fossil evidence suggests that palm extinctions
date back to the Palaeogene and Neogene periods and
new studies also highlight the impact of pre-Quaternary
historical drivers (Pan et al. 2006; Kiessling et al. 2012).
Blach-Overgaard et al. (2013) analysed a continental
data-set on African palms to explore the importance of
palaeoclimatic effects on current gradients associated
with their richness patterns. These authors found that
Figure 3. important herbaria storing samples of african palm taxa. (A) herbarium of the royal botanic Gardens, Kew (K); this
collection is in particular rich in east and South african taxa. (B) fruit collection of the herbarium of florence (fi), hosting many type
specimens described by odoardo beccari.
4
F. W. STAUFFER ET AL.
Figure 4. floristic inventory of the palms in Ghana. Borassus
aethiopum is a massive palm for which bulky specimens have
to be collected to obtain accurate morphological data. doudjo
ouattara, fred Stauffer and Patrick ekpe collected male and
female individuals of this species in different regions of the
country.
African palm diversity patterns show important historical legacies related to long-term climatic changes, in
particular pre-Pleistocene precipitation variables differentially affected current diversity patterns of palms
grouped by contrasting habitat requirements.
The present contribution, representing an expanded
version of the conference given in the frame of the
Tropical Botany Conference (Florence, October 2016),
aims to provide a general and updated picture on the
palm floristic and taxonomic studies on African palms,
focusing in particular on the recent efforts undertaken in
four West African countries (Côte d’Ivoire, Ghana, Togo
and Benin). In each of these countries the main goals
of the projects included: (1) a comprehensive floristic
inventory (including complete herbarium and DNA
sampling), (2) taxonomic definition of native palms and
a record of their morphological diversity, (3) an update
of distribution maps, (4) an inventory of the main uses
and common names, (5) conservation status assessment
following IUCN guidelines (country level assessment
as a first approach to a species level assessment), and
(6) morpho-anatomical studies on vegetative and/or
reproductive organs in poorly known or economically
important taxa. Although probably incomplete and lacking much more updated field data, we believe that the
present paper does contribute to a better understanding
of the palm family in Africa and may raise some interest
among the botanical research community.
2. Material and methods
The general taxonomic analysis on Continental African
palms is based on the complete or partial study of specimens deposited in the European herbaria of BR, BRU,
COI, FI, G, K, LISC, LISU and P, and the West African
herbaria of GC and the herbarium of the Swiss Research
Centre in Abidjan (Holmgren et al 1990). We have
largely benefited from the well-curated African database
of the WAG herbarium, as well as the complete database
of African plants from the Conservatory and Botanical
Garden of Geneva (https://www.ville-ge.ch/musinfo/bd/
cjb/africa/index.php?langue=fr). Taxonomic identification of specific palm groups was based on the publications
of Furtado (1967, Hyphaene), Barrow (1998, Phoenix),
Bayton (2007, Borassus), Dransfield (1986, 2010, East
African palms), Otedoh (1982, Raphia), Sunderland
(2012, African rattan genera), Van Valkenburg and
Sunderland (2008, Podococcus), Van Valkenburg et al.
(2008, Sclerosperma), Van Valkenburg and Dransfied
(2004, Hyphaene), and for other palm groups we based
our identifications on the general publication of Tuley
(1995). The general taxonomy and distribution of the
palms is based on the work of Stauffer et al. (2014).
For strictly practical reasons associated with our
analysis, some important geopolitical issues had to be
defined: Western Sahara was included under Morocco
and South Sudan was included in Sudan. Although our
study is restricted to Continental Africa and therefore
excludes Madagascar, some islands close to the continent
were included in our analysis. Hence, we have taken into
account the islands of Cape Verde, home of the endemic
Phoenix atlantica (Henderson et al. 2006), Sao Tomé &
Principes and Bioko (Equatorial Guinea), in the Guinea
Gulf and Pemba Island (Tanzania), home of the endemic
Dypsis pembana. Our analysis also takes into account the
palm genus Nypa; although this palm is well-known to
be native in South Eastern Asia (Dransfield et al. 2008) it
is nowadays spreading from Lagos to the Woury Estuary
near Douala.
The taxonomic, floristic, morphological, ecological
and ethnobotanic data associated with West African
palms is based on the results of three master projects
undertaken in the Conservatory and Botanic Gardens of
Geneva and the University of Geneva (Doudjo Ouattara:
palms of Côte d’Ivoire and Ghana), Simona da Giau
(palms of Côte d’Ivoire) and Loïc Michon (palms of
Togo and Bénin). Extensive field work associated with
palm research in West Africa was carried out in Senegal
(2014), Côte d’Ivoire (2012–2015), Ghana (2013–2015),
Benin (2014) and Togo (2015). Issued from these field
activities more than 150 fully informative herbarium
specimens are now deposited at G. For the ethnobotanical survey several interviews were carried out with
locals and village markets were visited; calculation of
the Relative Importance value for each species followed
the guidelines proposed by Bennett and Prance (2000)
and Albuquerque et al. (2006) and standardized forms
were inspired in Brokamp et al. (2010) and PaniaguaZambrana et al. (2010). We visited endangered or heavily
exploited palm populations and a preliminary conservation status assessment at country level for each species
was proposed based on Gärdenfors (2001) and IUCN
WEBBIA: JOURNAL OF PLANT TAXONOMY AND GEOGRAPHY
(2003). For the structural studies we have employed
the classical histological methods proposed in the laboratory of Micro-Morphology of the Conservatory
and Botanic Gardens of Geneva and scanning electron
microscope-based analyses by mean of the microscope
of the Natural History Museum of Geneva.
3. Results
3.1. A general overview on Continental African
palms
The Continental African palm flora is composed of 18
genera and 68 spp., about 60 of them are completely
endemic to the region; the most recent species discovered
and described is Laccosperma cristalensis Couvreur &
Niangadouma (Couvreur and Niangadouma 2016). The
subfamily Calamoideae, in particular with representatives in the tribes Lepidocaryeae (Ancistrophyllinae,
5
Raphiinae), and Calameae (Calaminae), is largely dominant with 62.68% of the taxa, whereas the subfamilies
Coryphoideae and Arecoideae are only represented by
22.38% and 13.42% of the taxa recorded for the area;
Nypa fruticans (Nypoideae) is in our analysis included
in this flora given its rapid expansion as an invasive plant
in Nigeria and Cameroon (Figure 5). The genera Raphia
and Hyphaene should be regarded as the main contributions by Africa to the palm family diversity. This incompletely understood genus is largely dominant with 20
species and is followed in the second place by the rattan
genus Eremospatha, represented by 11 species; the two
genera contribute with 46% of all African palm species
and are still common elements in well-preserved forests
of the tropical region (Figure 6).
It is very striking to note that almost half of all genera are monotypic, a condition that is only represented
to a very low degree in American or Asian palms. The
Figure 5. Palm sub-families and percentage of species per sub-family represented in the continental african palm flora. the subfamily nypoideae is here included given its rapid invasion in the shores of nigeria and Cameroon.
Figure 6. diversity of palm genera and species in africa. (A) Species reported in West africa (red bars) in comparison with the species
reported for the entire continent (green bars). (B) Raphia hookeri is a West african representative of the species-rich palm genus
Raphia, the latter regarded as the most important african contribution to the palm family.
6
F. W. STAUFFER ET AL.
African palm genera also show interesting facts with
respect to the way they are also represented in the palm
flora of other regions of the world. With respect to
endemism, seven palm genera are only present in continental Africa (Eremospatha, Jubaeopsis, Laccosperma,
Medemia, Oncocalamus, Podococcus and Sclerosperma).
On the other hand some African genera have been also
reported in continents such as South America (Elaeis,
Raphia), Europe (Chamaerops), Asia (Borassus, Calamus,
Hyphaene, Livistona, Phoenix), Madagascar (Borassus,
Dypsis, Elaeis, although its presence is still subject to
controversy, Hyphaene, Phoenix, Raphia) and Oceania
(Livistona).
3.2. Shared African–South American taxa: the
interesting cases of Elaeis and Raphia
The genera Elaeis and Raphia, shared between Africa
and South America, are worth discussing in detail. The
taxonomic identity of the South American member of
the genus Elaeis (Elaeis oleifera (Kunth) Cortés) is not
under debate as there are important features (i.e. growth
habit, infructescence architecture, fruit size and form)
supporting its separation from the well-known African
oil palm (Elaeis guineensis Jacq.). In the case of the genus
Raphia several authors support that the continent share
exactly the same species (Raphia taedigera); in Africa
this palm has been reported in Nigeria and Cameroon,
although according to Tuley (1995) it could also occur
anywhere near the coast and the nearby off-shore island
between the Niger and Congo deltas. The same author
also pointed out that this palm, at least based on the study
of African collections, may be probably better considered
as a variety of the closely related Raphia vinifera. The
presence and distribution of this species in eastern South
America (coastal Brazil) and southern Central America
have been documented by Henderson et al. (1995). This
palm belongs to the large Section Raphia (as defined by
Otedoh 1982), characterized by petioles and leaf rachis
of high quality and very durable thatch and with the
exception of Raphia africana generally not good for wine
production. The fruits in this Section are usually thick
and have an oil-rich edible mesocarp. All in all, it is clear
that the accurate taxonomic identification of the South
American and the African populations would be critical
to solving whether the populations present in the two
continents correspond to the same species or not. The
new project launched by Mogue and co-workers on the
genus Raphia, explained in detail later in this paper, will
probably contribute to our understanding of this matter.
towards the northern or southern latitudes, in which
the savanna areas are clearly dominant. Central Africa,
with 12 genera and 52 species, corresponds to the area
with the largest palm diversity; 24% the species present
there are endemics (Eremospatha barendii, Eremospatha
cabrae, Eremospatha cuspidata, Eremospatha tessmanniana, Laccosperma korupensis, Laccosperma robustum, Oncocalamus macrospathus, Oncocalamus mannii,
Podococcus acaulis, Raphia gentiliana, Raphia laurentii,
Raphia matombe, Raphia rostrata, Raphia sese, Raphia
textilis and Sclerosperma walkeri). West Africa follows
with 13 genera and 38 species, 9% of them being endemics (Eremospatha dransfieldii, Hyphaene macrosperma
and Oncocalamus wrightianus). East Africa is represented by 10 genera and 18 species, 18% of them endemics (Dypsis pembana, Hyphaene compressa and Livistona
carinensis). Northern Africa contributes to the African
palm flora with eight genera and nine species, 18% of
them endemics (Chamaerops humilis and Medemia
argun). Palm richness is lower in southern Africa, which
hosts six genera and seven species, only one them being
completely endemic (Jubaeopsis caffra) (Figure 7).
3.4. Analysis of some biological traits
Our analysis of the three important biological patterns
(growth form, reproductive strategy and leaf form) in
the 68 species concerned in our area of study showed
some interesting results. Continental African palms
display four different and more or less clearly defined
ways of growth form: erect and with an aerial stem is
3.3. Palm richness and endemism in the different
African sub-regions
Our analysis highlights that richness and endemism at a
continental scale concentrate in the tropical belt, where
forested areas are much better represented, and decrease
Figure 7. Palm richness present in the different sub-regions
of africa. the numbers in the pie charts refer to the number of
genera / number of species, and the percentage of endemism at
species level is indicated in brackets.
WEBBIA: JOURNAL OF PLANT TAXONOMY AND GEOGRAPHY
dominant (51%), climbing and lianescent habit (25%),
acaulescent to almost acaulescent (12%) and erect, with
a prostrate tendency (10%). For a few taxa (about 2%)
the type of growth form remains. An interesting case to
be mentioned is Raphia matombe De Wild, a palm that
has been only reported for Angola and the Democratic
Republic of Congo, for which the growth form has not
yet been described; cases like this should be investigated
in detail by means of further field work. The reproductive strategies observed in the African palm taxa are
diverse and expressed in four different ways: monoecy is
dominant (48%), whereas hermaphroditism (27%) and
dioecy (24%) are much less represented. The complex
polygamous–dioecious reproductive syndrome, which
requires in-depth study, has only been reported in northern African – Southern European palm Chamaerops
humilis. Leaf form is represented in four different ways:
pinnate leaves are clearly dominant (80%), whereas costa-palmate (17%), entire-bifid (2%) and palmate (1%)
are much less common.
We tried to perform an analysis of the dominant ecological conditions that prevail for each species; however,
this proved to be challenging as some taxa (i.e. Calamus,
Elaeis, Phoenix) may be adapted to relatively broad
conditions. Although approximately 40% of all African
palms prefer forested, warm and humid habitats, they
can also be represented in lowland savannas (coast and
inland savannas), mountain savannas, swamps and riverine areas, arid and semi-arid regions, rocky banks of
the rivers and disturbed–anthropogenic areas, among
others.
Incompletely understood and often under collected
African palm taxa are not necessarily associated with the
presence of massive stems (i.e. Borassus) or long leaves
(i.e. Raphia). More than half of the palms lacking morphological or ecological information belong to the rattan
groups, which combine climbing growth habit, they are
always spiny and often ant-associated by modifications
of the leaf sheath or the ochrea; all these features may at
least partially explain why access to informative vegetative or reproductive organs is strongly hindered. Poorly
known taxa are dominant in the genus Eremospatha, for
which comprehensive information on flowers and fruits
is not available for five out of the 11 species known in
the genus (Table 1). Indeed, as extensively explained in
many publications by Terry Sunderland (i.e. Sunderland
2007, 2012) sampling of informative herbarium specimens in rattan species is not an easy task because these
palms are strongly armed and flower far up in the canopy. The identification of reproductive organs in these
palms requires special skills, most often developed by
palm experts. Other factors that strongly hinder the collection of informative specimens are related to country
instabilities (i.e. civil wars, terrorist groups) or health
conditions (i.e. malaria, ebola outbreaks) predominant
in the countries were the palms grow.
3.5. Current research in West Africa: floristics,
systematics and structural botany, ethnobotany
and conservation
3.5.1. Taxonomic and floristic diversity
West Africa, as defined for our analysis, is composed
of 16 countries in which 13 genera and 39 palm species are present. Most of these palms are associated with
the different vegetation types present in the broadly
defined Upper Guinean Forest, a large vegetation unit
of c. 109,000 km2 hosting about 2800 vascular plants.
An important interruption to this now extremely fragmented forest belt is represented by the Dahomey gap,
extending from the Accra plains in Ghana to southern
Nigeria. In this region, the savannas reach the coast
and host species such as Borassus aethiopum, Hyphaene
guineensis, Phoenix reclinata and Raphia sudanica grow.
With respect to the palm flora, the richest country in
West Africa corresponds to Nigeria (32 spp.), where
Table 1. african palm species lacking critical morphological data associated with vegetative and reproductive organs. note that
almost half of species in the rattan palm genus Eremospatha are poorly known and require further collecting efforts.
Species
Eremospatha barendii Sunderl
Eremospatha dransfieldii Sunderl
Eremospatha hookeri (G. mann & h. Wendl.)
h. Wendl
Eremospatha quinquecostulata becc
Eremospatha tessmanniana becc
Hyphaene macrosperma h. Wendl
Hyphaene reptans becc
Laccosperma korupensis Sunderl
Oncocalamus wrightianus hutch
Raphia matombe de Wild
7
Distribution
Cameroon (Sunderland 2012)
West Ghana and east ivory Coast – outliers in
Sierra leone (Sunderland 2012)
northernmost part of the Congo basin (Sunderland 2012); presence in angola to be confirmed
(baker 2008)
from southeast nigeria through Cameroon
(Sunderland 2012)
Cameroon–nigeria border and cross border
region of Cameroon and equatorial Guinea
(Sunderland 2012)
northern benin
restricted to Kenya (reports to be confirmed in
Somalia and arabia)
restricted to Cameroon (Sunderland 2012)
South benin to southwest nigeria (Sunderland
2012)
from angola (Cabinda) to the southern region of
rdC (otedoh 1982; baker 2008)
Lacking data
flowers
inflorescences, flowers and fruits
flowers
flowers and fruits
flowers and fruits
Vegetative organs, inflorescence, flowers and
ecology
almost only known from the original description
(beccari 1908).
inflorescences, flowers and fruits
flowers and fruits
Growth habit and most leaf features unknown
8
F. W. STAUFFER ET AL.
Figure 8. floristic palm diversity, expressed in number of species, present in the different West african counties.
more field work, currently hindered by political instability, could highlight the presence of additional taxa.
Other countries such as Ghana (18 spp.), Côte d’Ivoire
(16 spp.), Benin and Liberia (15 spp.), rank among the
most diverse countries with respect to the palm family in the continent (Figure 8). In West Africa the most
frequently found species include the widely cultivated
Cocos nucifera (16 countries), the sun-tolerant rattan
palm Calamus deerratus (12 countries), the doum or
gingerbread palm Hyphaene thebaica (12 countries), the
raphia palm Raphia sudanica (11 countries), the African
oil palm Elaeis guineensis (10 countries), the forest rattan palm Laccosperma secundiflorum (10 countries), the
clustered date palm Phoenix reclinata (10 countries), and
the raphia palm Raphia farinifera (10 countries).
As indicated earlier in this paper, three species
(Eremospatha dransfieldii, Hyphaene macrosperma
and Oncocalamus wrightianus) are regarded as the
only endemic taxa of the region. In particular one of
them, Hyphaene macrosperma, requires further study
as it remains extremely poorly known. This palm is currently taxonomically accepted and reported as endemic
to Benin (Govaerts et al. 2017); its original description
was proposed by Wendland (1881) based on a single
fruit collected by Baikie. However in the publication
Flore analytique du Bénin Aké-Assi et al. (2006) did
not mention this species and cited Hyphaene thebaica
as the only species of the genus Hyphaene present in
that country. According to Furtado (1967), the fruit
was described as ovate rather obtuse, very smooth at
the top, slightly swollen on the ventral side, hardly ventricose, 7 cm long, 6 cm in diameter, resembling that of
Hyphaene thebaica but rounder, more obtuse and of a
duller colour. The seed was described as roundish ovoid,
45 mm long, 40 × 45 mm in diameter. Beccari (1908)
indicated that he studied the type specimen proposed
by Wendland and after comparison with its original
description he noticed that it corresponded well with
the description of Hyphaene dahomeensis Becc. (together
with Hyphaene nodularia Becc., one of the currently
accepted synonyms for the species), a name that has in
turn been proposed by several authors (i.e. Tuley 1995)
as a synonym of Hyphaene thebaica. In the frame of a
master project dealing with a floristic and systematic
study of the native palms in Togo and Benin (Michon
2017), the presence of Hyphaene macrosperma could
not be confirmed and only populations of Hyphaene
thebaica were spotted in the northernmost regions of
these countries. Current taxonomic efforts on the genus
Hyphaene (www.hyphaene.org) will probably show that
Hyphaene macrosperma, long regarded as an independent, yet poorly known taxonomic entity, can be rather
interpreted as a morphological variant of the widely distributed Hyphaene thebaica.
Other taxa requiring further studies are Borassus akeassi and Phoenix reclinata. According to Bayton et al.
(2006) Borassus akeassi is present in eight West African
countries, for which accurate characters supporting its
clear differentiation from the widespread Borassus aethiopum are still lacking. The clustered date palm Phoenix
reclinata, for which we have observed important growth
form variability (inland, tall individuals versus coastal,
almost acaulescent individuals) in countries such as
Senegal, Côte d’Ivoire, Togo and Benin needs to be studied in more detail. The taxonomic implications of the
high plasticity observed in this palm should be assessed
with the support of molecular phylogenetic studies and
with this aim we have been systematically collecting
material for DNA studies.
3.5.2 Structural botany
In the frame of a master project (Da Giau 2014), the
anatomy of Côte d’Ivoire rattan canes was studied in
several native species (Calamus deerratus, Eremospatha
WEBBIA: JOURNAL OF PLANT TAXONOMY AND GEOGRAPHY
Figure 9. one example of the histological studies carried out
on the rattan genera of Côte d’ivoire (da Giau 2014), in this
case on the cane of Eremospatha macrocarpa. (A) General view
of the stem with sheaths in cross-section, scale bar: 1 cm. (B)
Scanning electron microscope image of a portion of the stem,
cross-section, scale bar: 500 μm. (C) Stem in cross-section,
central cylinder; black arrow: protoxylem replacing metaxylem,
500 μm. (D) epidermis and cortex; cuticle (Cu); epidermis (e);
hypodermis (h); reduced vascular bundles (rVb), scale bar:
50 μm. (E) b-type ground parenchyma (GP) in cross-section
with the presence of a raphide sac (rS), scale bar 100 μm. (F)
Parenchyma in longitudinal section (GP), raphide sac (rS)
and fibres (f), scale bar: 200 μm. (G) two-vessel type with
one phloem (Ph) field; mx, metaxylem; Px, protoxylem; PP,
paratracheal parenchyma; f, fibres; scale bar: 500 μm.
laurentii, Eremospatha macrocarpa, Laccosperma acutiflorum, Laccosperma laeve, Laccosperma secundiflorum),
although one species of Oncocalamus (Oncocalamus
mannii (H. Wendl.) H. Wendl.), not reported for that
country, was also included in the study to have a representative of all African palm taxa (Figure 9). The main
aims of this study were to provide in-depth descriptions
of the anatomical features of stems of useful species, to
perform an identification key based on the anatomical
stem aspects and also to detect correlations between
the anatomical features and the quality of the Ivorian
canes. Based on several studied characters it was possible to clearly differentiate from an anatomical perspective members of the two tribes of Lepidocaryeae
(Calaminae and Ancistrophyllinae); the genus Calamus
9
shows an arrangement of phloem fields that is clearly
different from that of all members of Ancistrophyllinae
and this anatomical character could be useful to distinguish Calaminae to Ancistrophyllinae present in Africa.
Exploring affinities within Ancistrophyllinae demonstrated that the one-vessel structure of vascular bundles
observed in Oncocalamus and Laccosperma suggests a
close affinity between these two genera. Eremospatha
remains isolated with a two-vessel structure of vascular bundles; these results support some of the affinities
proposed by Faye et al. (2014) based on molecular phylogenetic studies. Calamus deerratus displays the best
histological characters associated with stem quality,
namely the presence of sections with even distribution of
the vascular bundles across the stem, moderate to high
values with respect to area covered by vascular bundles
and fibres, fibre walls showing high values of thickness
and stegmata lacking in peripheral vascular bundles.
Despite the optimal anatomical features displayed by
Calamus deerratus, in particular Côte d’Ivoire handcraft
makers prefer other rattans such as Eremospatha macrocarpa and Laccosperma secundiflorum. This may be at
least partially explained by the fact that the latter species
present better mechanical features that allow easier work
when bending the canes. All in all, other biomechanical
studies, such as the one proposed by Isnard and Rowe
(2008) and Isnard et al. (2005), should be performed on
African taxa to better understand the features taken into
account by handcraft makers when choosing canes of a
specific rattan, this information being critical for any
domestication programmes launched on these useful
species.
3.5.3 Palm uses and conservation
In West Africa palm resources rank among the most
appreciated Non-Timber Forest Products and contribute
significantly to household incomes of people, particularly those living in rural areas. As observed in several
native populations of Senegal, Côte d’Ivoire, Ghana,
Togo and Benin, palm organs can be classified under use
categories that include: edible, used for construction or
crafts, or even exploited for their medicinal or cosmetic
properties. On a more specific scale, those organs are
associated with several sub-categories including food,
beverage, oil, building/house construction, thatch, basketry, furniture, art craft, clothes, jewellery, medicinal
and cosmetic additives. The Relative Importance Index
(RI) was calculated for the native palms from Côte d’Ivoire and highlighted the species that were better represented in categories and sub-categories: the oil palm
Elaeis guineensis is at the top of the list (RI 2), meaning
that this species is by far the most economically important palm in that country (Figure 10). This species is
followed by Raphia hookeri (RI 1.8), Cocos nucifera (RI
1.6), Raphia sudanica (RI index 1.5) and Borassus aethiopum (RI 1.4). In the case of the latter, locals apparently
do not make any distinction with Borassus akeassi and
10
F. W. STAUFFER ET AL.
Figure 10. useful palms from West africa. in Côte d’ivoire, the oil extracted from the fruits and the seeds of the oil palm (Elaeis
guineensis) ranks among the most important palm products commercialized in the country. (A) Sun-dried fruits. (B) Women smashing
fruits. (C) Cooking of the smashed paste. (D) Paste pressing. (E) extracted red oil, still boiling. (didokro, Central Côte d’ivoire)
therefore, the uses reported may include the two species.
For the rattans reported to be used (i.e. Calamus deerratus, Eremospatha laurentii, Eremospatha macrocarpa,
Laccosperma laeve and Laccosperma secundiflorum) the
RI values are lower because those species do not present
edible organs.
The uses of West African palms are extremely diverse
and the demand for palm products is steadily increasing
in several countries. To meet the high market demand,
harvesting is done from wild populations and this raises
questions about their survival and sustainability. Today,
the majority of native palms in the region are exposed
to multi-factorial threats and about 90% of them are
not cultivated; only some examples of cultivated populations of Borassus aethiopum in the region of Thiès
(Senegal) highlight that the promotion and domestication of West African palms have a future. Although some
species can be found in agro-ecosystems (i.e. Hyphaene
guineensis), their management in these farmlands is not
convincingly sustainable. Many taxonomically interesting palms are not represented in protected areas, or if
they are, then they are present in only a few of them
(i.e. Sclerosperma profiziana in Ghana). Other species
are rare and economically important ones are intensively harvested from natural populations. Agriculture
and urban development has undergone unprecedented
expansion, drastically reducing forested areas and natural savannas. The conservation of African palms is a
real concern and the information associated with this in
the frame of our project aims to support local initiatives
WEBBIA: JOURNAL OF PLANT TAXONOMY AND GEOGRAPHY
11
Figure 11. Centre of environmental education and promotion of palm traditions in the City of divo (Côte d’ivoire). the dida ethnic
group makes important use of raffia fibres extracted from the leaves of Raphia hookeri. these traditional clothes are entirely woven
from raffia fibres and dyed with plants and mineral products. the City of Geneva Solidarity fund supports this centre and the
associated palm botanical garden, which is now under construction.
addressing conservation issues. An important effort is
currently being undertaken in the city of Divo (South–
Central Côte d’Ivoire) where the Conservatory and
Botanic Gardens in Geneva are developing an environmental centre focusing on the conservation of native
palms (rattans, Borassus aethiopum, Elaeis guineensis,
Raphia hookeri) and the promotion of palm-based products (Figure 11). Although mainly focused on the traditional and cultural practices associated with the Dida
ethnic group, this environmental centre aims to join
efforts at a country level, with palm representatives of
other regions in the country. An interesting conservation issue is related to the South-East Asian palm Nypa
fruticans, which has spread from Lagos to the Woury
Estuary near Douala (Cameroon). The palm was originally introduced from Singapore in 1906 and 1912 and
again 1946 (Sunderland and Morakinyo 2002; Beentje
and Bandeira 2007; Dransfield et al. 2008). According
to Tuley (1995) there are now reservations with regard
to its colonizing power as it could possibly be achieving
the status of a serious weed, to the exclusion of the native
mangrove species.
4. Future perspectives
We would like to finish this contribution by describing
current research efforts that focus on several interesting
aspects of African palms. Our project continues, providing new data on floristic and taxonomic aspects of
African palms and our permanent field missions to several countries of the continent offer new perspectives to
local and foreign researchers. The sampling efforts steadily increase our current knowledge of African palms, and
this is in particular true in the herbarium of Geneva (G),
which has now become the most important repository
of modern West African palm collections (about 150
new herbarium specimens). Here we present four interesting projects for which we provide direct or indirect
scientific collaboration. For all of them the Conservatory
and Botanic Gardens of Geneva (CJB) provide support
either by sampling efforts or offering direct advantages
for laboratory work; here below we briefly describe some
of these collaborations.
Raphia project (University of Yaoundé, IRD, CJB): In
the frame of a wide project including floristics, taxonomy and economic botany of the genus Raphia, the PhD
candidate Suzanne Mogue is undertaking a modern taxonomic revision of this interesting palm group (Figure
12). This work is supervised by Dr Thomas Couvreur
(IRD, France), Prof. Bonaventure Sonké (University of
Yaoundé), Dr Anders Barfod (Unversity of Aarhus) and
Fred Stauffer (CJB). In the frame of the monographic
study, Suzanne Mogue has also undertaken an in-depth
analysis of the morphology and anatomy of leaves and
flowers in Raphia (with emphasis in androecium structure), in search of taxonomically informative characters.
African palm phytoliths project (Universidad
Nacional de Colombia, CJB): Phytoliths are silica bodies that accumulate in the tissues of leaves and other
organs and remain in the soil for thousands or even millions of years. As already shown for Neotropical palms
(Morcote-Rios et al. 2016) they are widely used as proxies in the reconstruction of palaeo-environments and
ancient plant–animal and plant–human interactions. In
Africa, this is particularly interesting for hominid palaeontology, archaeology and palaeoecology, including
reconstruction of ancient landscapes. A collaboration
has been started with Gaspar Morcote and Lauren Raz
12
F. W. STAUFFER ET AL.
Figure 12. the ‘Raphia Project’. the Phd candidate Suzanne mogue (university of yaoundé – ird) undertakes floristic and taxonomic
research on the species-rich palm genus Raphia. (A) Raphia collecting in Cameroon. (B) the massive leaves of Raphia palms rank
among the longest in the Plant Kingdom; a comprehensive collection of these palms requires several hours of field work. (C) the
access to the ‘raphiales’ is not easy as these environments are often inundated during the rainy season. (D) Suzanne mogue has
carried out detailed morphological and anatomic studies on the leaves and the flowers of several species of Raphia. (laboratory of
anatomy of the Conservatory and botanic Gardens of Geneva)
Figure 13. a multi-disciplinary study of the palm genus Hyphaene. a monographic study of these palms is currently undertaken in
the Conservatory and botanic Gardens of Geneva. this image shows our collection of Hyphaene compressa in the region of lushoto.
(tanga region, tanzania) during 2016 (photo didier roguet).
(Universidad Nacional de Colombia) to produce an illustrated catalogue for all African genera, which includes at
least 45 species, with special emphasis on economically
important palms. In the frame of this collaboration the
phytolith morphotypes will be described and illustrated,
and their taxonomic distribution will be discussed along
with their potential for use in applied studies throughout
the continent.
A multidisciplinary study of the palm genus Hyphaene
(CJB): This is a project started in 2015 by the palm
research team of the Conservatory and Botanic Gardens
of Geneva. It aims to undertake a multidisciplinary study
on the palm genus Hyphaene (Coryphoideae: Borasseae),
which is apparently composed of eight species and ranks
among the most economically important, yet extremely
poorly known African palm genera. This palm group
was monographed about 90 years ago, and our project
aims to undertake modern taxonomic, morpho-anatomical, phylogenetic (collaboration with M. Perret
and Y. Naciri from CJB), ecological and conservation
WEBBIA: JOURNAL OF PLANT TAXONOMY AND GEOGRAPHY
studies of the group. Extensive sampling of informative
herbarium specimens and material for DNA studies
has been carried out in Ghana (2014), Djibouti (2015)
and Tanzania (2016, Figure 13), and new populations
will be sampled in South Africa during 2017. Extensive
sampling was also carried out in cultivated individuals
of the Montgomery Botanical Center and the Fairchild
Tropical Botanical Garden (Florida, USA).
Conservation status assessment of African palms
(IRD, Kew Gardens, CJB): Conservation issues associated with African palms have been discussed in the
frame of the floristic inventories carried out in Côte
d’Ivoire (Da Giau 2014), Ghana (Ouattara 2012; Ouattara
et al. 2014, 2015) and Togo and Benin (Michon 2017).
This relatively updated information is being used for a
more formal assessment of the conservation status of
African palms carried out by Oriane Cosiaux, Thomas
Couvreur and William Baker, in collaboration with our
team of CJB. The recent conservation status assessment
undertaken on the threatened rattan palm Eremospatha
dransfieldii (Cosiaux et al. 2017), is a good example of the
efforts that will be carried out for other African species.
Floristic, ecological and ethnobotanic studies of the
palms in the Democratic Republic of Congo (Faculty
of Sciences, University of Kinshasa): The Democratic
Republic of Congo shows, with 36 species, the second
most diverse palm flora in the continent; however, many
regions of the country remain under-collected and incompletely understood taxa, in particular in the genus Raphia
and most rattan groups, require further study. The PhD
candidate Pelagie Mbandu Luzolawo, supervised by Dr
Constantin Lubini Ayingweu and Fred Stauffer (CJB) is
currently undertaking extensive palm sampling to increase
our taxonomic and floristic knowledge of this group.
Acknowledgements
The present contribution would not have been possible
without the support of many people and institutions. Dr
Michel Grenon (Société de Physique et d’Histoire Naturelle
de Genève – SPHN) is greatly thanked for his permanent
support of our research on African palms. The Montgomery
Botanical Center (Patrick Griffith, Larry Noblick) and the
FTG (Carl Lewis, Chad Husby) largely supported my investigations on African palms in their important living collections.
An important team of African botanists have contributed to
the success of our field missions in several countries; among
them we are particularly indebted to Gabriel Ameka and
Prosper Avecor (University of Accra, Ghana), Zoul-Kifouli
Adeoti (University of Benin); Koffi Koudouvo (University of
Togo) and Frank Mbago (University of Dar es Salaam). In
the Conservatory and Botanical Gardens of Geneva we have
been supported by Laurent Gautier, Cyrille Chatelain and
Iacopo Luino. The International Palm Society Research Grant
kindly supported field work in Ivory Coast. John Dransfield
and William Baker (Kew Gardens), Thomas Couvreur (IRD),
Anders Barfod (University of Aarhus) and Marc Sosef (BR)
have contributed in different ways to the success of our investigations. We are also greatly indebted to the curators of the
herbaria of BR, BRU, COI, FI, G, K, LISC, LISU and P, and
13
the West African herbaria of GC and the Swiss Research
Centre in Abidjan. Dr Riccardo M. Baldini is deeply thanked
for his invitation to participate in the very successful Tropical
Botany Conference, held in Florence in October 2006.
Disclosure statement
No potential conflict of interest was reported by the authors.
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