A checklist of vascular plants of the W National Park in Burkina Faso, including the adjacent hunting zones of Tapoa-Djerma and Kondio

Blandine Nacoulma; Marco Schmidt; Karen Hahn; Adjima Thiombiano

doi:10.3897/BDJ.8.e54205

Biodiversity Data Journal : Taxonomic Paper

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Taxonomic Paper

A checklist of vascular plants of the W National Park in Burkina Faso, including the adjacent hunting zones of Tapoa-Djerma and Kondio

Blandine M. I. Nacoulma^‡, Marco Schmidt^§,|, Karen Hahn^¶, Adjima Thiombiano^‡

‡ Université Joseph Ki-Zerbo, Ouagadougou, Burkina Faso

§ Senckenberg Biodiversity and Climate Research Centre, Frankfurt am Main, Germany

| Palmengarten, Frankfurt am Main, Germany

¶ Goethe University, Frankfurt am Main, Germany

Corresponding author: Marco Schmidt (mschmidt@senckenberg.de)

Academic editor: Anatoliy Khapugin

Received: 12 May 2020 | Accepted: 18 Jun 2020 | Published: 03 Jul 2020

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: Nacoulma BMI, Schmidt M, Hahn K, Thiombiano A (2020) A checklist of vascular plants of the W National Park in Burkina Faso, including the adjacent hunting zones of Tapoa-Djerma and Kondio. Biodiversity Data Journal 8: e54205. https://doi.org/10.3897/BDJ.8.e54205

Abstract

Background

The W National Park and its two hunting zones represent a unique ecosystem in Burkina Faso for biodiversity conservation. This study aims at providing a detailed view of the current state of the floristic diversity as a baseline for future projects aiming at protecting and managing its resources. We combined intensive inventories and distribution records from vegetation plots, photo records and herbarium collections.

New information

This is the first comprehensive checklist of vascular plants of the Burkina Faso part of the transborder W National Park. With 721 documented species including 19 species new to Burkina Faso, the Burkina Faso part of the W National Park is, so far, the nature reserve with most plant species in Burkina Faso. To a large extent, this may be assigned to its high habitat diversity and moderate degree of disturbance, but also to a relatively large area within an even larger complex of neighbouring protected areas, as well as comprehensive spatial, ecological and seasonal sampling efforts. However, as a World Heritage Site and regarding the current general context of insecurity, the W National Park and the entire WAP Complex require more international attention in order to ensure its conservation.

Keywords

plant diversity; new species; flora of Burkina Faso; protected areas; WAP Complex; West Africa

Introduction

In times of growing land use pressure in West Africa, protected areas play an increasingly important role in the conservation of wildlife as well as plant species (Clerici et al. 2007, Zoungrana et al. 2018). The W-Arly-Pendjari Complex (WAP Complex) is the largest transborder complex of West African nature reserves shared amongst the three countries Benin, Burkina Faso and Niger and a World Heritage Site of the UNESCO (UNESCO World Heritage Committee 2017). The three partner countries seek to further optimise and formalise joint management systems for the regional park, which are already partially in place (Miller et al. 2015). Remote sensing studies (Schulte to Bühne et al. 2017) showed vegetation cover within the protected areas to remain relatively stable, while decreasing in the surroundings between 2000 and 2013. Due to agricultural expansion and intensification, especially in the context of cotton farming, the WAP Complex is becoming increasingly isolated (Clerici et al. 2007, Konrad 2015), leaving little space for near-natural habitats in the surrounding communal area, being composed of croplands, fallows of different ages and only few savannas in sites unsuitable for agriculture.

The complex is well-known for its role in the conservation of large mammals and typical Sudanian savanna ecosystems (e.g. Thiombiano et al. 2010, Thiombiano and Kampmann 2010, see next paragraph for more details). It is a continuous area of nine protected areas which include the trinational complex of W Regional Park (named after the course of the river Niger forming a “W” in this area), Arly National Park in Burkina Faso and Pendjari National Park in Benin connected and enlarged by protected areas of other categories and hunting reserves (Konrad 2015).

The wildlife, especially the large mammals (Lamarque 2004) and birds (Balança et al. 2007) of the WAP Complex, is well documented. Likewise, the flora of W National Park of Niger (Mahamane 2005), Arly (Ouédraogo et al. 2011), Pama (Mbayngone et al. 2008) and Pendjari (Assédé et al. 2012) have recently been documented by published checklists. The flora of the W National Park in Burkina Faso, however, remained scarcely and poorly documented.

The present checklist has been produced to fill this gap by providing a comprehensive and detailed view of the floristic diversity of the W National Park including the surrounding hunting reserves in Burkina Faso as a baseline for future projects aiming at protecting and managing the resources of the WAP Complex. We assume that the core area has a high plant diversity due to the geographical and climatic setting, as well as the diversity of its habitats.

Materials and methods

Study area

The W National Park (235,000 ha) and its two hunting reserves, Kondio (also called Kourtiagou 51,000 ha) and Tapoa Djerma (30,000 ha) are located in eastern Burkina Faso, between 12.4° and 11.4° N and 1.8° and 2.4° E (Fig. 1). The W National Park in Burkina Faso, together with its equivalents in Benin and Niger, constitute a transfrontier park that is designated “wetland of international importance” under the Ramsar Convention in 2007. Altogether, they are part of the larger W-Arly-Pendjari transfrontier complex shared amongst the three countries Benin, Burkina Faso and Niger and one of the most important West African transboundary Biosphere Reserves of UNESCO-MAB.

Figure 1.

Map of W National Park in Burkina Faso and adjacent hunting zones with georeferenced occurrence records, considering different geomorphological units.

Figure 2.

Species newly documented for the flora of Burkina Faso.

a: Ampelocissus bombycina (Photo by Meike Piepenbring)
b: Aponogeton vallisnerioides
c: Gladiolus unguiculatus
d: Indigofera garckeana
e: Jatropha atacorensis
f: Selaginella buchholzii

The national park belongs to IUCN Category II, whereas the hunting reserves belong to Category IV. Both categories act to protect large terrestrial and aquatic ecosystems, as well as threatened and rare species (both fauna and flora), serving as refuges and enhancing resilience. The National Park and the hunting zones are managed by prescribed fires ignited in October or November every year to mitigate the effect of accidental late fire and also to stimulate an off-season re-growth of perennial herbs for wildlife and to open the vegetation and increase the visibility of animals for tourists.

The W National Park and the two adjacent hunting zones of Burkina Faso are located in the Sahelo-Sudanian climate zone with an average rainfall of 750 to 950 mm, annual mean temperatures between 26 and 29°C and a dry season of 6-7 months. It belongs to the Pendjari-Mekrou biogeographical sector, shared between the Volta basin in its southern part and the Niger basin in the north. In the central western part of W National Park, eastern outliers of the Gobnangou range reach into the park and eastern outliers of the Atakora mountains are located on the southern edge of Kondio reserve and W National Park. The largest rivers in the reserves are the Mekrou on the eastern border and the Tapoa in the north, both tributaries of the Niger. In addition to the artificial water points, there are also numerous natural pools, with permanent and/or temporary water regimes (PNUD 2004). The vegetation is composed of a mosaic of various types of savannas i.e. woodland, grass, shrub and tree savanna, dry and gallery forests (Fontès and Guinko 1995), mostly distributed along elevation and soil gradients (Nacoulma et al. 2011) .

Data collection and management

The checklist is a result of extensive field surveys by the first author during the years 2007-2010, (622 records from a species list based on 369 vegetation plots; Nacoulma 2012), as well as photo records (545 records; Dressler et al. 2014, Schmidt et al. 2016) and herbarium collections from the W National Park, including the herbaria of OUA, FR (733 and 583 records via their respective collection databases) and WAG (five records via GBIF). The vegetation plots followed standard sizes of 10 m x 10 m for the herb layer and 10 m x 50 m or 30 m x 30 m for the woody layer shown to be suitable for the characterisation of Sudanian savanna vegetation by Hahn-Hadjali (1998) and Ouédraogo (2006). They were taken mostly during the end of the rainy season (September-October) in order to maximise the number of flowering individuals for identification. The smaller plots for herbs were randomly located inside the corresponding plots for woody plants. The locations were chosen by a stratified random design using satellite images and soil maps to best represent the geomorphological units (colluvial plains: 5, floodplain: 17, lower slope glacis: 45, mid-slope glacis: 101, upper slope glacis: 54, hardpan hillocks: 18, hardpan glacis: 73, shallows: 31, sandstone hills: 25) and vegetation types (woodland: 39, gallery forest: 17, savanna woodland: 58, tree savanna: 92, shrub savanna: 134, grass savanna: 29) following the definitions of the Yangambi conference (Conseil Scientifique pour l'Afrique au Sud du Sahara 1956), while taking accessibility into account (see Fig. 1 for the plot locations and geomorphological units). Herbarium and photo records were partly taken during the afore-mentioned work on vegetation plots, partly during collecting expeditions for the assessment of Burkina Faso's flora, focussing on previously under-sampled habitats (van der Burgt et al. 2010) and in the course of other research in the area with different focus (Erpenbach et al. 2012, Schumann et al. 2016, Zwarg et al. 2012). For data analysis, all these records have been combined into an MS Access database. Species concepts and synonymy, as well as families, follow Thiombiano et al. (2012) and, for orthographic corrections of primary data, we used the Taxonomic Name Resolution Service (TNRS; http://tnrs.iplantcollaborative.org). In order to identify species new to the flora of Burkina Faso, we compared the total floristic list of the study area to the catalogue of Burkina Faso‘s vascular plants (Thiombiano et al. 2012), supplemented by new species records from Schmidt (2018). Introduced species have been identified using a list extracted from Thiombiano et al. (2012), based upon distribution notes and contributed to the Global Register of Introduced and Invasive Species (Schmidt et al. 2020).

Species identification

Species have been identified using the Flora of West Tropical Africa (Hutchinson and Dalziel 1972), Flore Analytique du Bénin (Akoegninou et al. 2006), as well as group-specific literature for grasses (Poilecot 1995, Poilecot 1999), orchids (Perez-Vera 2003) and woody plants (Arbonnier 2000) in combination with online guides such as African Plants - a photo guide (Dressler et al. 2014) and the herbarium collections of Ouagadougou University (OUA) and Herbarium Senckenbergianum (FR).

Notes on the checklist

The list is arranged alphabetically by family and species. Synonyms are only given if these have been used in our primary data in herbarium, vegetation plot or photo records. Herbarium records are given with collector and collector’s number, followed in parentheses by herbarium code and herbarium number. Photo records are marked with APPG (African Plants - a photo guide: Dressler et al. 2014) and the photo ID within the guide’s website and database. New country records are specifically mentioned as "New species record for Burkina Faso". Introduced species are marked by "(introduced)" following the distribution type.

Vascular plants of W National Park, Burkina Faso and adjacent hunting zones

Annona senegalensis Pers.

Distribution:

Sudanian

Notes:

Life Form: phanerophyte; Voucher: Zwarg 73 (FR)

Hexalobus monopetalus (A.Rich.) Engl. & Diels

Distribution:

Sudanian

Notes:

Life Form: phanerophyte; Voucher: Nacoulma 147 (OUA-13511)

Uvaria chamae P.Beauv.

Distribution:

Pluriregional African

Notes:

Life Form: phanerophyte; Voucher: Nacoulma 4949 (OUA-17281)

Xylopia aethiopica (Dunal) A.Rich.

Distribution:

Guineo-Congolian-Sudano-Zambesian

Notes:

Life Form: geophyte

Stylochaeton hypogaeus Lepr.

Distribution:

Sudanian

Notes:

Life Form: geophyte; Voucher: Nacoulma (APPG-70382)

Stylochaeton lancifolius Kotschy & Peyr.

Distribution:

Aristolochia albida Duch.

Distribution:

Kigelia africana (Lam.) Benth.

Distribution:

Sudano-Zambesian

Notes:

Life Form: phanerophyte; Voucher: Nacoulma 107 (OUA-13471)

Stereospermum kunthianum Cham.

Distribution:

Euploca strigosa (Willd.) Diane & Hilger

Distribution:

Paleotropical

Notes:

Life Form: chamaephyte; Voucher: Nacoulma 4476 (OUA-17054)

Heliotropium indicum L.

Distribution:

Pantropical

Notes:

Life Form: therophyte; Voucher: Nacoulma (APPG-70063)

Rotula aquatica Lour.

Distribution:

Wahlenbergia hirsuta (Edgew.) Tuyn

Distribution:

Afro-American

Notes:

Life Form: therophyte; Voucher: Schumann (FR-0083327)

Family Cannabaceae

Trema orientalis (L.) Blume

Distribution:

Polycarpaea corymbosa (L.) Lam.

Distribution:

Pluriregional African

Notes:

Life Form: therophyte; Voucher: Nacoulma 94 (OUA-13458)

Polycarpaea eriantha Hochst. ex A.Rich.

Distribution:

Sudano-Zambesian

Notes:

Life Form: therophyte; Voucher: Schumann (FR-0083322)

Polycarpaea linearifolia (DC.) DC.

Distribution:

Afrotropical

Notes:

Life Form: therophyte; Voucher: Schumann (FR-0083321)

Polycarpon prostratum (Forssk.) Asch. & Schweinf.

Distribution:

Parinari congensis Didr.

Distribution:

Guineo-Congolian

Notes:

Life Form: phanerophyte; Voucher: Schmidt et al. (FR-0007622)

Costus spectabilis (Fenzl) K.Schum.

Distribution:

Distribution:

Distribution:

Sudano-Zambesian

Notes:

Life Form: therophyte

Eriocaulon plumale N.E.Br.

Distribution:

Distribution:

Afrotropical

Notes:

Life Form: therophyte; Voucher: Zwarg 41 (FR)

Family Gentianaceae

Canscora diffusa (Vahl) R.Br. ex Roem. & Schult.

Distribution:

Sudano-Zambesian

Notes:

Life Form: therophyte; Voucher: Nacoulma 105 (OUA-13469)

Distribution:

Sudano-Zambesian

Notes:

Life Form: geophyte; Voucher: Nacoulma 69 (OUA-13433)

Gladiolus unguiculatus Baker

Distribution:

Pluriregional African

Notes:

Life Form: geophyte; Voucher: Nacoulma (APPG-70039); New species record for Burkina Faso.

Family Isoetaceae

Isoetes nigritiana A. Braun

Distribution:

Utricularia inflexa Forssk.

Distribution:

Paleotropical

Notes:

Life Form: therophyte; Voucher: Nacoulma 4488 (OUA-17066)

Utricularia stellaris L.f.

Distribution:

Paleotropical

Notes:

Life Form: hydrophyte; Voucher: Zizka (APPG-3900)

Family Linderniaceae

Lindernia exilis Philcox

Distribution:

Agelanthus dodoneifolius (DC.) Polhill & Wiens

Distribution:

Sudanian

Notes:

Life Form: epiphyte

Tapinanthus bangwensis (Engl. & K.Krause) Danser

Distribution:

Guineo-Congolian

Notes:

Life Form: epiphyte; Voucher: Nacoulma (APPG-6855)

Tapinanthus globiferus (A.Rich.) Tiegh.

Distribution:

Distribution:

Afro-American

Notes:

Life Form: phanerophyte; Voucher: Zwarg 22 (FR)

Family Marantaceae

Thalia geniculata L.

Distribution:

Martynia annua L.

Distribution:

Glinus lotoides L.

Distribution:

Pantropical

Notes:

Life Form: hemicryptophyte; Voucher: Nacoulma 176 (OUA-13540)

Mollugo nudicaulis Lam.

Distribution:

Syzygium guineense (Willd.) DC.

Distribution:

Afrotropical

Notes:

Life Form: phanerophyte; Vouchernomenc: Nacoulma 152 (OUA-13516)

Family Nyctaginaceae

Boerhavia erecta L.

Distribution:

Ochna schweinfurthiana F.Hoffm.

Distribution:

Sudano-Zambesian

Notes:

Life Form: phanerophyte; Voucher: Nacoulma 15 (OUA-13386)

Family Oleaceae

Jasminum obtusifolium Baker

Distribution:

Ophioglossum costatum R. Br.

Distribution:

Sudano-Zambesian

Notes:

Life Form: geophyte; Voucher: Nacoulma 246 (OUA-17234)

Ophioglossum reticulatum L.

Distribution:

Pantropical

Notes:

Life Form: geophyte; Voucher: Zizka (APPG-3435)

Ophioglossum thomasii R.T. Clausen

Distribution:

Sudano-Zambesian

Notes:

Life Form: geophyte; Voucher: Nacoulma 230 (OUA-17238); New species record for Burkina Faso.

Family Opiliaceae

Opilia amentacea Roxb.

Distribution:

Distribution:

Sudano-Zambesian

Notes:

Life Form: therophyte; Voucher: Schumann (FR-0083124)

Family Oxalidaceae

Biophytum umbraculum Welw.

Distribution:

Ceratotheca sesamoides Endl.

Distribution:

Peperomia pellucida (L.) Kunth

Distribution:

Plumbago zeylanica L.

Distribution:

Polygala arenaria Willd.

Distribution:

Pluriregional African

Notes:

Life Form: therophyte; Voucher: Zwarg 9 (FR)

Polygala multiflora Poir.

Distribution:

Sudanian

Notes:

Life Form: therophyte; Voucher: Nacoulma 87 (OUA-13451)

Securidaca longipedunculata Fresen.

Distribution:

Eichhornia natans (P.Beauv.) Solms

Distribution:

Afro-American

Notes:

Life Form: therophyte; Voucher: Nacoulma 4498 (OUA-17068)

Heteranthera callifolia Rchb. ex Kunth

Distribution:

Afro-American

Notes:

Life Form: therophyte; Voucher: Nacoulma 4591 (OUA-17185)

Monochoria brevipetiolata Verdc.

Distribution:

Anagallis pumila Sw.

Distribution:

Paleotropical

Notes:

Life Form: therophyte; Voucher: Schmidt et al. (FR-0007697)

Family Pteridaceae

Ceratopteris cornuta (P. Beauv.) Lepr.

Distribution:

Zanthoxylum zanthoxyloides (Lam.) Zepern. & Timler

Distribution:

Manilkara multinervis (Baker) Dubard

Distribution:

Pluriregional African

Notes:

Life Form: phanerophyte; Voucher: Nacoulma 109 (OUA-13473)

Mimusops kummel Bruce ex A.DC.

Distribution:

Sudanian

Notes:

Life Form: phanerophyte

Sphenoclea zeylanica Gaertn.

Distribution:

Pouzolzia guineensis Benth.

Distribution:

Pantropical

Notes:

Life Form: phanerophyte; Voucher: Schmidt et al. (FR-0007631)

Family Violaceae

Hybanthus enneaspermus (L.) F.Muell.

Distribution:

Composition of the local flora

The 721 species found in the study area belong to 385 genera and 102 plant families, the families with most species being Fabaceae (126 spp.), Poaceae (102 spp.) and Cyperaceae (44 spp.) (Fig. 3). The genera with most species in the study area are Indigofera (20 spp.), Crotalaria (17 spp.) and Acacia (13 spp.), all belonging to Fabaceae.

Figure 3.

Family spectrum of the flora of the W National Park with number of species for the 10 largest plant families in the study area and all remaining families.

Therophytes and phanerophytes are the most prominent life forms, followed by hemicryptophytes, geophytes and chamaephytes (Fig. 4). Only very few hydrophytes and epiphytes are present.

Figure 4.

Life form spectrum of the flora of the W National Park.

The best represented distribution types in the flora are specific to the vegetation zone, either Sudanian or Sudano-Zambesian (Fig. 5). Species with wider distributions in the tropics (pantropical, paleotropical) or within continental Africa (afrotropical, pluriregional African) follow. The remaining distribution types have smaller shares and comprise either distributions extending to other continents or Madagascar or belong to the neighbouring zones under higher rainfall regimes, typically extending into the Sudan along gallery forests of the larger watercourses.

Figure 5.

Distribution types of the flora of W National Park: sudanian (S), sudano-zambesian (SZ), pantropical (Pan), paleotropical (Pal), afrotropical (AT), pruriregional African (PRA), afro-malagasy (AM), guineo-congolian (GC), afro-american (AA), guineo-congolian/sudano-zambesian (GC-SZ), cosmopolitan (Cos), of cultivated origin (Cul).

New species records for Burkina Faso

A number of species have been found in the study area that have not been documented in the vascular plant catalogue of Burkina Faso (Thiombiano et al. 2012), nor in the supplement by Schmidt (2018); some of these are shown in Fig. 2. These 19 species are Aponogeton vallisnerioides (Aponogetonaceae), Drimiopsis barteri (Asparagaceae), Eleocharis naumanniana (Cyperaceae), Jatropha atacorensis, Tragia laminularis (Euphorbiaceae), Aeschynomene americana, Alysicarpus vaginalis, Crotalaria lachnophora, Desmodium ramosissimum, Indigofera garckeana, Vigna nigritia (Fabaceae), Gladiolus unguiculatus (Iridaceae), Ophioglossum thomasii (Ophioglossaceae), Chloris gayana, Loxodera ledermannii (Poaceae), Salix chevalieri (Salicaceae), Selaginella buchholzii (Selaginellaceae), Synaptolepis retusa (Thymelaeaceae) and Ampelocissus bombycina (Vitaceae). The number of vascular plants known for Burkina Faso therefore increases to 2099 species.

Red Lists

Unlike for neighbouring Benin (Neuenschwander et al. 2011), there is no country-specific Red List for Burkina Faso yet. Amongst the 14 species listed for Burkina Faso on the global IUCN Red List (IUCN 2020) in the categories endangered (EN), near threatened (NT) or vulnerable (VU), the following occur in our study area: Pterocarpus erinaceus (EN), Afzelia africana (VU) and Khaya senegalensis (VU).

Introduced species

Amongst the species occurring in the study area, 17 species have been identified as being introduced: Acanthospermum hispidum, Ageratum conyzoides, Azadirachta indica, Bidens pilosa, Cassia obtusifolia, Chrysanthellum indicum, Desmodium adscendens, Hyptis spicigera, H. suaveolens, Indigofera microcarpa, Ludwigia erecta, Martynia annua, Passiflora foetida, Plumbago zeylanica, Scoparia dulcis, Spermacoce verticillata and Tridax procumbens. The families best represented in this group are Asteraceae (5 spp.) and Fabaceae (3 spp.).

Discussion

With 721 documented species, the Burkina Faso part of the W National Park is, so far, the most species-rich nature reserve in Burkina Faso. Neither the protected areas of the same Sudano-sahelian climatic zone nor those in the Sudanian climatic zone have an equally-high diversity. In the Sudano-sahelian zone, the reserve of Pama and Arly National Park sustain 450 and 490 species, respectively (Mbayngone et al. 2008, Ouédraogo et al. 2011), whereas the classified forests of Kou and Niangoloko, as well as the classified forest and partial faunal reserve of Comoé-Léraba in the Sudanian zone, have 353, 275 and 521 species, respectively (Guinko and Thiombiano 2005, Ouôba 2006, Gnoumou et al. 2015).

Several factors might explain this: to a large extent, the high plant diversity can be assigned to habitat diversity and a moderate degree of disturbance, but also to a relatively large area within an even larger complex of neighbouring protected areas. In Burkina Faso, the study sites are known for the diversity of their natural habitats, i.e. the Gobnangou and Atakora mountains, wetlands and gallery forests, termite mounds as well as anthropogenic relics of the past. Anthropogenic relics are still visible with metallurgical sites and baobab vegetation types, being closely linked to human settlements as shown by Duvall (2007).

Thorough spatial, ecological and seasonal sampling have certainly contributed to a good documentation of the area, building on experiences from similar studies in protected areas and focussed collection activities for the documentation of the flora of Burkina Faso (van der Burgt et al. 2010).

Finally, based on different scenarios, recent investigations (Schmidt et al. 2017) identified the southeast of Burkina Faso, around the W National Park, as one of the two hotspots of plant diversity of the country. Our present results confirm and strengthen these scenarios. There are no species endemic to W National Park and Isoetes jaegeri, the only plant still recognised as endemic to Burkina Faso does not occur here, being known exclusively from the sandstone massif in the southwest of the country. Including the 19 newly-documented species, the W National Park harbours more than one third of the plant diversity known for Burkina Faso, making it an important area for plant conservation in a landscape setting where biodiversity outside of protected areas is increasingly threatened by intensified agriculture (Zoungrana et al. 2018). At the country level, Da et al. (2018) evaluated the percentage of modelled plant species distributions covered by protected areas and came up with a figure of 77% for Burkina Faso. Our results confirm the importance of these reserves for plant conservation with primary biodiversity data.

The composition of the flora by families, life forms and distribution types follows the same patterns as in other protected areas of the WAP complex (Assédé et al. 2012, Mbayngone et al. 2008, Ouédraogo et al. 2011). The dominance of Fabaceae and Poaceae may be explained by their respective innovations in N-fixation and C₄-photosynthesis, making them well-adapted to savanna environments. Therophytes and phanerophytes are the dominant life forms here and in the wider area of the West African savanna belt, with therophytes being more important in the drier north and phanerophytes in the wetter south (Schmidt et al. 2005). The large proportion of widespread species in West African savanna areas like the W National Park may be explained by the dominance of the savanna vegetation in a vast continuous band throughout West Africa in combination with the lack of effective barriers, such as higher mountains which separate savanna areas in other parts of Africa (White 1983).

Only few species from Burkina Faso have been Red-listed by IUCN, the three species in the W National Park all being sought-after timber species. The IUCN Red List is a good instrument to target species for conservation measures.However, only few species of the West African Flora have been evaluated, for Burkina Faso less than 20% (400 out of 2099 spp., IUCN 2020). Continued efforts will be necessary to get a better idea on threats and necessary conservation measures and a prerequisite are scientifically reliable assessments, accessible to the community and representing important parts of the region.

The number of 17 introduced plant species (2.3%) is rather low when compared to the 116 introduced species (5.5%) on the country scale (Zizka et al. 2015). It shows the success of these neophytes in protected areas under limited anthropogenic influence and may stimulate research on introduction routes and more in-depth studies on neobiota in Burkina Faso in general.

Acknowledgements

Fieldwork for this study was funded by the SUN-project (FP7 INCO-dev 031685). We are grateful to all foresters and guides of the Provincial and Departmental Forestry Office in Diapaga and especially to Commanders Célestin P. Zida and Zacharia Traoré, our „W park fathers“ for all their assistance during the fieldwork. A special thank you to Dr Dimobé Kangbeni for editing the map of the study area. A grant by the „Ministère des Enseignements Supérieurs et de la Recherche Scientifique (MESRSI)“ of Burkina Faso provided funds to stay at Palmengarten/Frankfurt for processing the data and drafting the manuscript. Finally, we thank Dr. Clemens Bayer, Deputy Director of Palmengarten for the invitation and Dr. Stefan Dressler of Senckenberg Natural History Museum Frankfurt for identification of herbarium samples.

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