Floristics of the angiosperm flora of Sub-Saharan Africa: an analysis of the African Plant Checklist and Database

TAXON 56 (1) February 2007: 201 208 Klopper & al. Sub-Saharan angiosperm flora BIODIVERSITY AND CONSERVATION Floristics of the angiosperm flora of Sub-Saharan Africa: an analysis of the African Plant Checklist and Database Ronell R. Klopper 1, Laurent Gautier 2, Cyrille Chatelain 2, Gideon F. Smith 3 & Rodolphe Spichiger 2 1 National Herbarium, South African National Biodiversity Institute, Private Bag X101, Pretoria, 0001 South Africa. klopper@sanbi.org (author for correspondence) 2 Conservatoire et Jardin botaniques de la Ville de Genève, case postale 60, 1292 Chambésy, Switzerland 3 Office of the Chief Director: Research and Scientific Services, South African National Biodiversity Institute, Private Bag X101, Pretoria, 0001 South Africa / Acocks Chair, Schweickerdt Herbarium, Department of Botany, University of Pretoria, Pretoria, 0002 South Africa The African Plant Checklist and Database Project (APCD) provides botanists with the first angiosperm checklist and database for Sub-Saharan Africa. This was achieved by merging the existing datasets for Southern and Tropical Africa. The checklist is published as a one-off hardcopy publication. The database, with all attached additional information, is freely accessible via the internet and will be regularly updated. The APCD, for the first time, gives accurate statistics for the angiosperm flora of Sub-Saharan Africa. There are 50,136 current taxa (representing approximately 44,830 species) in the database, plus an additional 393 taxa where there are discrepancies in genus concept between the two original datasets. Taxa are classified into 274 families and 3,802 current genera. Several other important statistics can also be drawn from the database. Furthermore, by pointing out problems and discrepancies in taxonomic opinion, the APCD highlights taxa where further research is necessary. The APCD will be an invaluable tool to botanists working on the African flora. It also has an important role to play in greater projects such as the Global Plant Checklist Project and has already emerged as a nomenclatural standard for the African Plants Initiative. KEYWORDS: angiosperms, checklist, database, floristics, Southern Africa, Sub-Saharan Africa, Tropical Africa BACKGROUND Up-to-date information on biodiversity is critical for the proper management and conservation of any area. Thus, the first step towards conservation should be to compile a species inventory or checklist. Despite this obvious value, very few complete checklists exist for most continents or mega-regions of the world, with Africa being no exception. The African Plant Checklist and Database project (APCD) is a collaboration between the South African National Biodiversity Institute (SANBI) and the Conservatoire et Jardin Botaniques of the city of Geneva, Switzerland (CJBG). The project was conceived at the XIV th Congress of the Association pour l Etude Taxonomique de la Flore d Afrique Tropicale (AETFAT) held at the Wageningen Agricultural University in the Netherlands from 22 27 August 1994 (for a complete history of the project, see Gautier & al., 2006). The primary objective of the project was to combine two major datasets, namely: (1) the Flora of Southern Africa (FSA) dataset (Germishuizen & Meyer, 2003), and (2) the Lebrun & Stork (1991, 1992, 1995, 1997), Enumération des Plantes à Fleurs d Afrique Tropicale (EPFAT) publications and their follow-up, Tropical African Flowering Plants, Ecology and Distribution (Lebrun & Stork, 2003), covering Tropical Africa. The result is the first-ever angiosperm checklist and database for Sub-Saharan Africa, currently excluding the surrounding islands (Fig. 1). The first output of the APCD is a hardcopy publication of the checklist (Klopper & al., 2006). This is a milestone in the project and will be published only once. The second and long-term output is a searchable database that is freely accessible via the internet. It will be permanently updated, regularly incorporating additions and corrections. The merged database is housed at CJBG: http://www.ville-ge.ch/cjb/bd/africa. There is also a link to the database on the SANBI website: http://www.sanbi. org/frames/infofram.htm. The database will serve as a backbone to which other information can be attached. In this respect, the website already includes additional information, such as short descriptions, ecological notes and distribution maps (for certain families). 201

Klopper & al. Sub-Saharan angiosperm flora TAXON 56 (1) February 2007: 201 208 Fig. 1. Map showing the area covered by the APCD, as well as the areas of the two original datasets: Flora of Southern Africa (FSA) and Enumération des Plantes à Fleurs d Afrique Tropicale (EPFAT). SIMILAR PROJECTS There are various country checklists available for all types of plants (vascular and non-vascular) from all around the world. Complete continental or near-continental checklists, on the other hand, are not as commonly available, especially not for the vascular plants. Most of the global or regional checklists that are currently being produced are static lists, with no means of keep them up-to-date (Crane, 2004). The main reason for this is that very few are linked to an informative, updatable database. Although some projects do have informative databases, they are not always freely accessible via the internet. Two examples of continental or near-continental checklist projects that are in some ways similar to the APCD are Synthesis of the North American Flora and The Australian Plant Names Index. The Synthesis of the North American Flora (http:// www.bonap.org/synth.html) has been developed over the past 30 years by the North Carolina Botanical Garden. The database contains information on the nomenclature and taxonomy of the 28,000 known native and naturalised vascular plants of North America north of Mexico, an area of approximately 21.5 million km 2 (Qian, 1999). It also contains the associated synonyms (in total nearly 75,000 names), as well as phytogeographical, morphological and other data. The goal of the Australian Plant Names Index (APNI) (http://www.anbg.gov.au/cpbr/databases/apni.html) is to achieve free and universal on-line access to information about Australian plants through an authoritative compilation of plant names, providing a foundation resource for botanical and environmental research, education and public interest. APNI is the standard dataset for plant names in Australia and contains more than 80,000 names. The Australian continent is thought to have around 20,000 taxa on an area of about 7.6 million km 2 (Frodin, 2001). Apart from nomenclatural and taxonomic information, the website also contains links to other information such as distribution, descriptions and images. The APCD is much bigger than both these initiatives, not just in the area covered by the checklist, but also in the number of taxa. The total land area of Sub- Saharan Africa is 23.7 million km 2, slightly bigger than North America north of Mexico and reasonably bigger than Australia. The APCD database currently contains a total of almost 110,000 names of which more than 50,000 are currently accepted names, slightly less than double that of the Synthesis of the North American Flora and more than double that of Australia. However, the main aim to present a continental or near-continental checklist with additional information is very similar among these three projects. On a broader scale, the Global Plant Checklist Project (http://plantnet.rbgsyd.gov.au/iopi/iopigpc1.htm) is an international co-operative project with the aim of producing a global checklist of the world s plants by 2010. This is the first target of the Global Strategy for Plant Conservation (GSPC). Its first priority is the vascular plants (about 300,000 taxa and over 1,000,000 names), but eventually the checklist will also include non-vascular plants (Secretariat of the Convention on Biological Diversity, 2002). Compiling a global working list of accepted plant names is a huge endeavour and has many obstacles (Nic Lughadha, 2004), but it is long overdue and various efforts have already been made in this direction. The APCD can also have an important role to play in the GSPC, by providing an angiosperm checklist for Sub-Saharan Africa. HYBRIDS, CULTIVATED TAXA AND DISCREPANCIES Hybrids and cultivated taxa. Hybrids have always been difficult to deal with taxonomically. This is mostly due to the problems in identifying hybrids and especially hybrid swarms, as opposed to infraspecific variation of morphologically and ecologically varied species. At present there are a total of 366 hybrid taxa in the APCD database. The database also contains 653 taxa that are flagged as cultivated in one of the regions. Although the 202

TAXON 56 (1) February 2007: 201 208 Klopper & al. Sub-Saharan angiosperm flora EPFAT publications include cultivated taxa, the FSA publications do not. Therefore, most cultivated taxa in the database are from the EPFAT region where 649 taxa have been flagged as such. A full account of the cultivated taxa in Southern Africa can be found in Glen (2002). Although hybrids and cultivated taxa are included in the APCD database, a decision has been made to omit these taxa from the hardcopy publication of the checklist. Only indigenous and naturalised taxa appear in the publication. Therefore, the statistics given here also exclude all hybrids and cultivated taxa in the database and are only for the indigenous and naturalised taxa that appear in the checklist. Taxa that are indigenous to or naturalised in one region, but cultivated in the other are included in the statistics and checklist. However, only their indigenous or naturalised status is taken into account, while their cultivated status in the other region is ignored. Discrepancies. These are taxa where there is a discrepancy in genus concept between FSA and EPFAT. Reconciling conflicting taxonomic opinions about the correct circumscription of taxa is one of the major obstacles that are mentioned when discussing the preparation of global-scale checklists of accepted names (Nic Lughadha, 2004). Discrepancies in the APCD amount to less than 1% of all current taxa (including infraspecific taxa) in the database. This is much less than the estimated 10% at species level cited in the literature (Nic Lughadha, 2004). It is not the intention of this project to resolve these discrepancies. However, where there is a discrepancy in the taxonomic opinion between FSA and EPFAT, the outputs of the project have been designed to reflect both taxonomic views in parallel. This practice, in no way, detracts from the usefulness of the checklist as a nomenclatural standard. Only a very small amount of taxa (1% of taxa currently in the database) show discrepancies in genus concept, while by far the majority (although a mere 200 cases) of the additional parallel views, indicate different opinions at the infraspecific level (for instance taxa only dealt with at species level in one region, but at infraspecific level in another). These parallel views, highlight taxa where further research is necessary. It is hoped that future taxonomic treatments and expert reconciliation will resolve these discrepancies and provide a 100% consensus list for the convenience of the end-user. ANALYSIS OF THE APCD Data from the APCD are here analysed for Sub- Saharan Africa as a whole. It would be tempting to analyse the data at a second level, i.e., to compare figures coming from the FSA and EPFAT datasets, but this comparison would be based on a limit that does not correspond to a biogeographical boundary. The region covered by FSA includes not only the Cape Floristic Region, but also a significant proportion belonging to the Paleotropical Floristic Region. The respective figures of the two datasets are nevertheless presented in the tables, but for the above-mentioned reason, one should refrain from drawing biological conclusions on their basis. Families. Predictably, there are some clear discrepancies as to family concepts between FSA and EPFAT. Families are mainly a practical means of arranging genera, and therefore binomials, and besides, are often subject to numerous changes in circumscription (Angiosperm Phylogeny Group, 1998, 2003). In this respect, the use of a standard emerged as the simplest way of handling this problem. Therefore, when the family concepts of the two datasets were similar, that view was followed, but when the family concepts differed, Brummitt (1992) was followed. In the APCD, taxa are classified into 269 families (Table 1). The largest family in Sub-Saharan Africa is the Fabaceae, followed by the Asteraceae and Rubiaceae (Table 2). Most families in Sub-Saharan Africa (67%) have less than 100 taxa in the area, but contain only 7% of the taxa in the region. Of these smaller families 13% have only one taxon and 21% have between 11 and 50 taxa in Sub-Saharan Africa. A further 26% of families have between 100 and 1,000 taxa and hold 36% of the taxa in the region. Only 5% of families have more than 1,000 taxa, but they hold 57% of the taxa in Sub-Saharan Africa (Fig. 2.A). Genera. There are 3,802 genera containing current names in the database (Table 1). Erica (Ericaceae) is the largest genus in Sub-Saharan Africa, followed by Euphorbia (Euphorbiaceae) and Crotalaria (Fabaceae) (Table 2). As with the sizes of families, the sizes of genera in Sub-Saharan Africa are also skewed towards small numbers of taxa per genus. No less than 33% of genera Table 1. General statistics for the angiosperms of Sub- Saharan Africa. S, Southern Africa, FSA region; T, Tropical Africa, EPFAT region; * includes discrepancies; 1 does not include 2 & 3. Monocots Dicots Total Families 60 209 269 Current genera 762 3,040 3,802 Current taxa 10,879 39,257 50,136 Discrepancies 136 257 393 Taxa occurring in both S and T 1,284 3,366 4,650 Taxa occurring in S only 4,131 13,780 17,911 Taxa occurring in T only 5,464 22,111 27,575 Total number of taxa in S* 5,483 17,272 22,755 Total number of taxa in T* 6,816 25,608 32,424 Taxa naturalised in Sub-Saharan Africa 1 165 1,256 1,421 Indigenous in T, naturalised in S 2 38 100 138 Indigenous in S, naturalised in T 3 9 33 42 203

Klopper & al. Sub-Saharan angiosperm flora TAXON 56 (1) February 2007: 201 208 Table 2. Five largest families and genera in Sub-Saharan, Southern and Tropical Africa. Number of current taxa plus total number of discrepancies given in brackets after the family or genus name. Sub-Saharan Africa Southern Africa Tropical Africa Families Fabaceae (5,154 + 55) Asteraceae (2,499 + 14) Fabaceae (3,793 + 31) Asteraceae (4,323 + 24) Fabaceae (1,865 + 24) Rubiaceae (2,381) Rubiaceae (2,521 + 2) Mesembryanthemaceae (1,748) Asteraceae (2,164 + 10) Poaceae (2,189 + 19) Iridaceae (1,153) Poaceae (1,795 + 5) Euphorbiaceae (1,988 + 4) Poaceae (955 + 14) Euphorbiaceae (1,645 + 2) Genera Erica (981) (Ericaceae) Erica (947) (Ericaceae) Crotalaria (542) (Fabaceae) Euphorbia (764 + 2) (Euphorbiaceae) Aspalathus (334) (Fabaceae) Euphorbia (507 + 2) (Euphorbiaceae) Crotalaria (570) (Fabaceae) Senecio (312 + 2) (Asteraceae) Vernonia (378 + 4) (Asteraceae) Indigofera (504 + 3) (Fabaceae) Euphorbia (304) (Euphorbiaceae) Indigofera (354 + 1) (Fabaceae) Senecio (452 + 2) (Asteraceae) Helichrysum (259) (Asteraceae) Psychotria (251) (Rubiaceae) Fig. 2. Number of families, genera and taxa in different size classes. A, number of families and taxa defined according to the number of taxa in a family in Sub-Saharan Africa; B, number of genera and taxa defined according to the number of taxa in a genus in Sub-Saharan Africa. have only one taxon in the area. As much as 77% of genera have less than 10 taxa, while only 7% of genera have more than 40 taxa. When examined from the perspective of species, 17% of taxa in Sub-Saharan Africa belong to genera with less than 10 taxa in the region, while 59% of taxa belong to genera with more than 40 taxa in Sub- Saharan Africa (Fig. 2.B). Number of taxa. Despite the fact that our knowledge of the extremely diverse African flora is far from complete, the available information base is still more advanced than those for either tropical America or Asia (Morat & Lowry, 1997). It has been estimated that Africa harbours 40,000 50,000 vascular plant species, but possibly as many as 60,000 species (Davis & al., 1994). However, certain estimates even go as high as 74,000 species (Govaerts, 2001). This higher number includes species in North Africa, Macaronesia and the West Indian Ocean islands, including Madagascar. All these areas are excluded from the current project and the calculated number for only Southern and Tropical Africa will therefore not be as high. The APCD, for the first time, gives an accurate assessment of the number of angiosperms in Sub-Saharan Africa (Table 1). The database contains 50,136 current names, representing approximately 44,830 species. This number compares well with the above-mentioned estimates. A total of 4,650 taxa are shared between the FSA and EPFAT regions. This amounts to a 9% overlap of taxa between the two regions (Table 1). Govaerts (2001) estimated a total of 21,030 seed plant species for Southern Africa and 29,887 for Tropical Africa. The APCD shows that Southern Africa has a total of 22,755 angiosperm taxa and Tropical Africa 32,424 (Table 1). The abovementioned estimates were therefore not too far off, but were indeed under- rather than over-estimates. It is, however, important to emphasise that the Govaerts estimates are for seed plants (gymnosperms and angiosperms) at species level, while the APCD figures given here are for angiosperm taxa (including infraspecific taxa). Infraspecifics account for roughly 10% of the total number of taxa. If this percentage is deducted from the APCD totals to obtain an estimate of the number of species, the figures approach the Govaerts estimates more closely. However, the 1% discrepancies (393 taxa) have to be added to the 50,136 current names. Endemicity. A ±10% family endemicity has been estimated for the African continent and according to literature ±6% of African genera are continental endemics (Davis & al., 1994). It is, however, difficult to calculate family and genus endemicity from the APCD database, since some families and genera may have representatives in other areas of the world and this is not recorded in the database. Preliminary investigations showed that at least 25 families (9%) are endemic to Sub-Saharan Africa (Ta- 204

TAXON 56 (1) February 2007: 201 208 Klopper & al. Sub-Saharan angiosperm flora Table 3. Families endemic to Southern and Tropical Africa, as well as families that occur in both regions that are endemic to Sub-Saharan Africa. Number of current taxa given in brackets after the family name. Families endemic to Families endemic to Other families endemic to Southern Africa (11) Tropical Africa (8) Sub-Saharan Africa (6) Achariaceae (3) Cyclocheilaceae (4) Behniaceae (1) Bruniaceae (78) Dioncophyllaceae (3) Eriospermaceae (131) Geissolomataceae (1) Huaceae (3) Heteropyxidaceae (3) Greyiaceae (3) Lepidobotryaceae (1) Melianthaceae (18) Grubbiaceae (6) Medusandraceae (8) Montiniaceae (1) Lanariaceae (1) Octoknemaceae (7) Vahliaceae (17) Penaeaceae (28) Pentadiplandraceae (2) Prioniaceae (1) Scytopetalaceae (22) Rhynchocalycaceae (1) Roridulaceae (2) Stilbaceae (13) ble 3). This compares well with the estimated family endemicity cited in the literature. These endemic families are mostly small families with only a few taxa. No less than 16 endemic families have fewer than five taxa. The largest of the endemic families are the Eriospermaceae, Bruniaceae, Penaeaceae and Scytopetalaceae (Table 3). There are also several near-endemic families with only a few representatives outside the region, for instance Dirachmaceae and Oliniaceae, each with one species on Socotra and St. Helena respectively. Several other families also have their centres of diversity in Sub-Saharan Africa, e.g., Restionaceae and Mesembryanthemaceae (Mabberley, 1990). In the APCD there are 48,715 (97%) taxa indigenous to Sub-Saharan Africa. It has been stated that around 35,000 species are endemic to the African continent, giving a species endemism of 58 88% (Davis & al., 1994; Klopper & al., 2002). As with family and genus endemicity, it is, unfortunately, difficult to calculate endemism from the APCD database since some of the indigenous taxa may extend to North Africa, Arabia, Western Asia, Europe and other areas outside the scope of this project and are therefore indigenous, but not endemic to Sub- Saharan Africa. Naturalised taxa. Estimates of naturalised taxa for Sub-Saharan Africa are not widely available, and the numbers published for Tropical Africa (536 species, 2.2%) and Southern Africa (824 species, 3.9%) were originally taken from the FSA and EPFAT publications (Vitousek & al., 1997). In the APCD there are a total of 1,421 taxa (2.8%) that have been naturalised in Sub- Saharan Africa (Table 1). This is more than the combined total of the published numbers for FSA and EPFAT, and includes some overlapping taxa naturalised in both areas. Of the 1,421 taxa flagged as naturalised in Sub-Saharan Africa in the APCD database, 310 are naturalised in both Southern and Tropical Africa, 508 in Southern Africa only and 603 in Tropical Africa only. This gives a total number of 818 taxa (3.6%) naturalised for the FSA region and 913 taxa (2.8%) for the EPFAT region. The previous estimations were therefore slightly higher for FSA, but were under-estimated by almost 40% for Tropical Africa. It should, however, be kept in mind that the published numbers, especially those for FSA, were for vascular plants, while the APCD only deals with angiosperms. The Fabaceae has the highest number of naturalised taxa in Sub-Saharan Africa, followed by the Asteraceae and Poaceae (Table 4). The following six families are Table 4. Five families and genera with the highest number of naturalised taxa in Sub-Saharan, Southern and Tropical Africa. Number of naturalised taxa in each region given in brackets after the family or genus name. Numbers for Southern and Tropical Africa exclude taxa that are indigenous in one region and naturalised in the other. Sub-Saharan Africa Southern Africa Tropical Africa Families Fabaceae (289) Asteraceae (99) Fabaceae (226) Asteraceae (136) Fabaceae (94) Asteraceae (63) Poaceae (115) Poaceae (88) Poaceae (51) Euphorbiaceae (57) Solanaceae (34) Euphorbiaceae (49) Solanaceae (56) Brassicaceae (31) Solanaceae (40) Genera Acacia (31) (Fabaceae) Solanum (19) (Solanaceae) Cassia (31) (Fabaceae) Cassia (31) (Fabaceae) Acacia (16) (Fabaceae) Acacia (27) (Fabaceae) Solanum (28) (Solanaceae) Oenothera (15) (Onagraceae) Passiflora (22) (Passifloraceae) Passiflora (24) (Passifloraceae) Taraxacum (15) (Asteraceae) Solanum (22) (Solanaceae) Euphorbia (21) (Euphorbiaceae) Trifolium (15) (Fabaceae) Euphorbia (18) (Euphorbiaceae) 205

Klopper & al. Sub-Saharan angiosperm flora TAXON 56 (1) February 2007: 201 208 completely naturalised in Sub-Saharan Africa, with no indigenous taxa in the area: Acoraceae, Agavaceae, Cannabaceae, Fagaceae, Liliaceae (s.str.) and Myoporaceae. The two genera with the most naturalised taxa in Sub- Saharan Africa are Acacia and Cassia (both Fabaceae), followed by Solanum (Solanaceae) (Table 4). An interesting fact drawn from the APCD database is that, apart from the above-mentioned taxa that have been naturalised in Sub-Saharan Africa, there are 138 Tropical African taxa, in 41 families, that are naturalised in the FSA region. There are also 42 FSA taxa, in 20 families, that are naturalised in Tropical Africa (Table 1). The families with the highest number of indigenous taxa from one region that have been naturalised in the other, are the Poaceae for EPFAT taxa naturalised in Southern Africa, and the Fabaceae for FSA taxa naturalised in Tropical Africa (Table 5). It has been shown in various parts of the world that there is a definite link between plant invasions and human activity, e.g., gardening, horticulture and human traffic. It has also been shown that developing countries have fewer alien species than developed countries (Vilà & Pujadas, 2001). Most of the naturalised weeds in Southern Africa have initially been used as ornamentals (Henderson, 2006). Southern Africa, and especially South Africa, probably had a longer history of gardening and cultivation than most of Tropical Africa. This might explain the higher number of Tropical African taxa that have been naturalised in Southern Africa. Comparing the diversity. The total surface area for Sub-Saharan Africa is 23.7 million km 2. Thus, for an estimated world flora of 422,127 (Govaerts, 2001) the region contains approximately 12% of the world flora on 18% of the total land area. Floristic diversity can be compared by assuming an exponential species-to-area relationship to determine a regional diversity index. This index is calculated with the following formula: D = S/logA, where S is the number of taxa in the region, and A the area of the region in square kilometres (Keith & al., 1999). To put this index in a global context it has to be compared with similar figures for other tropical and sub-tropical mega-units and continents (Fig. 3.A). Sub-Saharan Africa has the second highest regional diversity index of all the areas being compared. Only South America has a higher index. If the log-number of taxa is plotted against log-area for the same mega-units and continents, this diversity can be more easily compared (Fig. 3.B). Results are similar to those of the regional diversity index. South America lies far above the trend line, followed by Greater Malesia, Sub-Saharan Africa and Southeast Asia, all above the trend line. However, floristic diversity is not evenly distributed throughout the continent and the flora of Sub-Saharan Africa shows a high degree of patterning (Linder, 2001; Van Wyk & Smith, 2001). For instance, Tropical Africa contains small areas of primary rainforest that have among the highest species : area counts recorded for any vegetation type on Earth (Davis & al., 1994). Seven of the 34 biodiversity hotspots recognised worldwide occur in Sub-Saharan Africa (Meyers & al., 2000; Mittermeier & al., 2004). They are the Cape Floristic Region, the Succulent Karoo, the Maputaland-Pondoland-Albany region, the Guinean Forests (formerly the Western African Forests), the Coastal Forests of Eastern Africa, the Eastern Afromontane region (the latter two previously combined as the Eastern Arc) and the Horn of Africa (Cowling & Hilton-Taylor, 1994; Meyers & al., 2000; Mittermeier & al., 2004). There are also 235 Table 5. Families with the highest number of indigenous taxa from one region that are naturalised in the other region. Number of naturalised taxa in each region given in brackets after the family name. EPFAT taxa naturalised FSA taxa naturalised in FSA in EPFAT Poaceae (31) Fabaceae (9) Asteraceae (27) Poaceae (7) Fabaceae (12) Malvaceae (3) Brassicaceae (8) Geraniaceae (2) Polygonaceae (4) Onagraceae (2) Oxalidaceae (2) Portulacaceae (2) Rubiaceae (2) Fig. 3. Comparing the diversity of Sub-Saharan Africa with that of various other tropical and sub-tropical mega-units and continents (data for other regions taken from Frodin, 2001). A, regional diversity index; B, taxon-area relationship. 206

TAXON 56 (1) February 2007: 201 208 Klopper & al. Sub-Saharan angiosperm flora centres of plant diversity recognised worldwide (Davis & al., 1994). These are endemic-rich botanical areas of global conservation significance. A total of 84 of these centres occur in Africa, of which 14 are located in Southern Africa and 70 in the rest of Africa. However, the 14 Southern African centres cover by far the largest surface area (±50%) of these important sites in Africa (Davis & al., 1994; Van Wyk & Smith, 2001). The strong skewing of endemism and species richness towards the south indicates that fluctuations in the Sahara might have had a strong influence on plant distributions in Africa. The existing centres of endemism can therefore be seen as refugia from glacial aridity (Linder, 2001). The African flora, and especially its patterns of endemism and species richness, has long attracted interest. Now that a checklist and database with additional information for the angiosperms of Sub-Saharan Africa is available, it will aid studies on the African flora and will enhance results from such research. FUTURE ACTIVITIES The APCD is not a static list of names, but a database that will be constantly updated and expanded. New taxa and results from new taxonomic revisions will be implemented in the database on a regular basis. The additional information on the website, including short descriptions, condensed ecological notes and draft distribution maps, are already available for most FSA taxa and for some EPFAT taxa. This information will be improved and added for the other families as it becomes available. Efforts are already being made to include the angiosperms of North Africa. This will provide a complete continental checklist for the flowering plants of Africa. Further groups that will be included in the APCD in the near future are the gymnosperms and pteridophytes. The possibility of including the small islands surrounding the continent is also being investigated. CONCLUSIONS The APCD gives an accurate indication of the number of angiosperm taxa in Sub-Saharan Africa for the first time, and several important statistics can be drawn from the database. In most cases, previous estimations of the floristic diversity of the African continent compare well with the numbers provided by the APCD. This shows that the methods used to approximate species numbers for large areas are effective. The checklist does not aim to solve all taxonomic problems, but will rather highlight taxa where future research is necessary. The end-products of the project will be invaluable to taxonomists working on the African flora and will probably represent a critical step towards a better understanding of the African flora. The increasing number of biological databases available on the internet demonstrates that it is possible to overcome the various obstacles to compiling large-scale checklists and accompanying datasets. The APCD is but one example of such a dataset. This near-continental angiosperm checklist and database is a step in the direction of meeting the needs of the GSPC for a global plant checklist. Furthermore, in a recent project aiming to digitize all African type specimens and associated information (African Plants Initiative, Smith, 2004), the APCD is emerging as a nomenclatural standard for Africa south of the Sahara. ACKNOWLEDGEMENTS We thank the following people for their contributions, without whom the project would not have made such good progress: Helen Neveling for capturing EPFAT data in the database at PRE; Hester Steyn for quality-controlling the EPFAT data at PRE before they were sent to G; Carole de Wet for designing the databases and merging programs at PRE; Valérie Bänninger and Christine Habashi for editing the EPFAT database at G; Marc Ottone for helping to design the database at G; Sharareh Salman-Manesh and Laurent Kneubühl for designing the database interface and Website at G. Furthermore, we would like to thank SABONET and the Andrew W. Mellon Foundation for their involvement and financial contributions towards the project. LITERATURE CITED Angiosperm Phylogeny Group. 1998. An ordinal classification for the families of flowering plants. Ann. Missouri Bot. Gard. 85: 531 553. Angiosperm Phylogeny Group. 2003. 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