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Commercialization of Aframomum spp. in Africa: a Systematic Review of Literature and Supporting Botanical Vouchers

Abstract

Aframomum (Zingiberaceae) is a genus of plants native to tropical Africa that are sold on African markets as spices and traditional medicine. Not all species of Aframomum are equally abundant or widespread, and no overview exists of the specific species traded or the quality of the species identifications in publications referencing the sale of Aframomum. Through a systematic literature review, we show that 14 species of Aframomum are sold in 15 African countries. The majority of the studies were done in Nigeria and Cameroon and A. melegueta was the most frequently reported species in trade. A. kayserianum was the only commercialized species with confirmed conservation issues. Our literature review shows extensive knowledge gaps regarding the commercialization of Aframomum in Africa. Most studies did not include herbarium vouchers, or only used market-sourced plant material, which impedes the possibilities for species verifications. Additionally, most East African countries were devoid of relevant research. These gaps can be bridged by future research in East Africa and voucher collection from living material. Information on the conservation status of traded Aframomum species can be obtained by population studies on wild resources and documenting local domestication efforts, as the cultivation of marketed species tends to relieve the pressure from wild resources.

Introduction

Aframomum K.Schum. is a genus of 62 plant species in the family of Zingiberaceae that occurs in the rainforests and savanna areas of tropical Africa and Madagascar (Fischer et al. 2017; Harris and Wortley 2018). Wild Aframomum generally occurs in the undergrowth and along the edges of tropical forest. It is an herbaceous plant that grows to approximately 1.5 m in height (Harris and Wortley 2018). The different species vary widely in their flower display, but all Aframomum species produce flask-like pods that contain aromatic, peppery seeds (Fig. 1). Species from this genus have been an important source of food and herbal medicine since antiquity. The seeds of Aframomum, also known as alligator pepper, melegueta pepper or grains of paradise, have been exported to Europe since the thirteenth century, where they were sold as condiment (Van Harten 1966). The extent of this trade becomes evident from maps of Africa from the 17th and eighteenth century, on which Sierra Leone, Liberia and parts of Ivory Coast are often indicated as “Grain Coast”, “Pepper Coast” or “Melegueta Coast”, referring to the grains of paradise (Hepper 1967; Moll 1729). At present, seeds from Aframomum spp. have largely lost their popularity as a spice in Europe (Eyob et al. 2009), although the fruits and seeds can still be found in African food shops in migrant neighbourhoods in Paris and Brussels (Tabuna 1999; Van Andel and Fundiko 2016). In their native range around the African equator, however, many parts of Aframomum spp. are available on markets and their sale has been asserted as an important local income generator (Ingram et al. 2010; Menbere et al. 2019; Ngansop et al. 2019). The dried fruits and seeds are generally sold as a spice, while many other parts of the plants, such as the rhizomes and leaves, are used as traditional medicine for both humans and cattle (Quattrocchi 2012). Leaves of Aframomum spp. are also used on markets as packaging material (Ingram 2016).

Fig. 1
figure1

Useful plant parts in the genus Afromomum: A) Fruit of cultivated Aframomum melegueta individual (Suriname); B) Fruits of Aframomum daniellii, wild individual, Cameroon; C) Open fruits of Aframomum subsericeum, wild individual, Cameroon; D) Leaves of Aframomum subsericeum, wild individual, Cameroon. Pictures: Tinde van Andel (A), Sandrine Gallois (B, C, D).

The plant material of Aframomum spp. offered for sale in African markets is sourced from both wild and cultivated plants. Four species of Aframomum are reported to be cultivated: A. melegueta (Roscoe) M. Schum., A. corrorima (A.Braun) P.C.M. Jansen, A. exscapum (Sims) Hepper and A. angustifolium K.Schum. (FEWS NET n.d.; Furo et al. 2020; Harris and Wortley 2018; Jansen 1981). A. melegueta, which occurs throughout Africa’s equatorial West coast, is grown as a domesticated crop in large quantities in Ghana, both as a cash crop and for subsistence use (Harris and Wortley 2018; Lock et al. 1977). A. corrorima is widely cultivated in Ethiopia, which alongside Kenya, Uganda, Burundi and Tanzania makes up the native range of this species (Harris and Wortley 2018). A. exscapum is likewise mentioned as a cultivated species by Harris and Wortley (2018), although no region of cultivation is mentioned. Lastly, A. angustifolium is cultivated in Ethiopia (Furo et al. 2020). Commercialized material from these species can thus be harvested from cultivated individuals, but also from wild resources, as these species still occur in in the wild in the same areas. All other species sold on African markets are sourced from natural populations from tropical rainforests or savannas. In spite of the various cultivation efforts, Aframomum products are often regarded as non-timber forest products (NTFPs) or produits forestiers non ligneux (PFNL) in French. NTFPs are defined as wild products harvested from forests or other natural or disturbed vegetation types, except for industrial timber (Ticktin 2004).

Wild Aframomum species are not all equally abundant and widespread. A. angustifolium for example is a common sight along forest edges and roadsides from Ivory Coast to Madagascar (Crook et al. 2019; Harris and Wortley 2018). Other species have a very small range, such as A. kodmin D.J. Harris & Wortley, or are declining in abundance due to anthropogenic threats, as is the case for A. laxiflorum Loes. ex. Lock (Harris et al. 2019a; Harris et al. 2019b). According to the IUCN Red List, the conservation status of Aframomum species ranges from Least Concern (39 species) to Vulnerable (seven species) and Endangered (ten species), alongside five species that are considered Data Deficient (IUCN 2020). The population decline of Aframomum species that are only found in the wild may be problematic for people who collect these species as NTFPs, but also for the survival of local wildlife. Aframomum fruits and leaves are an important food source for both gorillas and chimpanzees (Calvert 1985; Wrangham et al. 1994). Indeed, the clearing of vegetation along logging roads in the Central African rainforest by timber companies has already led to a decline in Aframomum species along forest edges and the spread of the invasive species Chromolaena odorata (L.) R.M.King & H.Rob., which is not eaten by large primates (Van der Hoeven 2007).

Given the importance of Aframomum for both humans and wildlife, the variations in conservation status within the genus and the fact that some species are harvested from the wild while others are cultivated, it is important to assess which species of Aframomum are actually sold in Africa. Understanding whether the trade in Aframomum depends on cultivated plants, abundant wild species, or on species that are threatened or restricted in their range will help to prioritize species for sustainability assessments.

While evaluating any conservation concerns, it is important to assess to which extent the identifications of commercially harvested Aframomum species are based on botanical vouchers. This is essential because Aframomum has been frequently misidentified in herbaria (Goodwin et al. 2015). Investigating whether or not the species identifications are based on herbarium specimens will show what portion of the identifications can be verified through morphological analysis or through DNA barcoding. Many vouchers have already been revised for the recently published monograph of Aframomum by Harris and Wortley (2018), who combine taxonomic data with reports on range and abundance, notes on ecology and ethnobotanical practices. The authors also revised the Red List conservation status for every Aframomum species. The revision by Harris and Wortley (2018) has made it considerably easier to compare mentions of trade and conservation issues, thereby making this review possible.

Through a systematic literature review, we aim to assess which species of Aframomum are reported as being sold on African markets, in which countries these sales occur, and to what extent these observations are based on herbarium vouchers. This literature review explores whether the trade in Aframomum species depends on wild NTFPs or on cultivated individuals, thereby examining if the commercialization might pose a risk to the conservation of the species. Finally, we identify where the largest knowledge gaps occur and what can be done to bridge those gaps. This literature review is the first step towards a complete overview of the trade in Aframomum spp. in Africa and possible associated conservation concerns.

Materials and Methods

Aframomum occurs in tropical Africa from Senegal to Madagascar. In this review, we considered the sale of Aframomum in all African countries, both inside and outside the natural range of Aframomum. To retrieve literature mentioning the sale of Aframomum spp. in Africa we used four data sources: Web of Science (WOS), SCOPUS, Google Scholar and Prelude. We planned to search for literature through WOS, SCOPUS and Prelude only. However, after comparing the resulting publications with the hits for the aforementioned search term in Google Scholar, it became obvious that they differed substantially. We therefore felt the need to supplement our systematic literature review with a search into Google Scholar. Only the first 40 articles were assessed, as the relevance of the hits sharply declined after that point. For WOS and SCOPUS, we used the following search query: (“Aframomum” OR “Afromomum” OR “alligator pepper” OR “melegueta” OR “maniguette” OR “malagueta” OR “grains of paradise” OR “grains-of-paradise” OR “graine de paradis” OR “poivre de Guinée” OR “false cardamom” OR “korarima”) AND (“NTFP” OR “PFNL” OR “market*” OR “ethnobotan*” OR “trade” OR “spice”).

This query was used to search the title, keywords and abstract of the documents available in these databases. This included peer-reviewed articles, conference publications, reports and books. We did not include restraints concerning language or year of publication. We purposely also used the incorrect name Afromomum, as the genus is often misspelled in publications. A modified search query was used in Google Scholar due to its 128-character limit for search terms. The search query was as follows: “Aframomum” AND (“NTFP” OR “PFNL”) AND “Africa”. No other constraints were applied to this search.

The final database that we utilized in this review was the Prelude database (Baerts-Lehmann and Lehmann n.d.), which contains published and unpublished articles and reports about the use of medicinal plants in Africa. The database can be searched by plant name, country, medical symptom or reference. We searched Prelude using the search term “Aframomum”. No constraints regarding language or year of publication were implemented.

All unique hits that were generated using these four search engines were assessed in two rounds. In round one, we searched for evidence of trade of any Aframomum species in any African country in the title, abstract, keywords, and in the main text if necessary. If there was a direct mention of sale of any species of Aframomum in Africa, or if the study was based on interviews where herb sellers represented the majority of the respondents, the study was passed on to round two. Publications that never identified any Aframomum material to species level were discarded. Likewise, publications of which the full text was not available through the internet (using the access portals of Utrecht University, Naturalis Biodiversity Center, Wageningen University and the University of Amsterdam) were rejected. In round two, we scanned the entire publications for data on sale of Aframomum spp. in Africa. For every study, we recorded the species name, country of sale (including market location if disclosed), presence of voucher material (including the herbarium where the voucher was deposited and the voucher number), the origin of the collected material (from living plant material or from a market), whether the material was from a wild or cultivated plant and whether the product sold on the market was called a NTFP (or PFNL). This last observation was included to identify possible instances of confusion for species that are both collected from the wild and cultivated. Additionally, we checked if the country of sale was within the natural range of the species in question according to Harris and Wortley (2018). Afterwards, we matched all species mentioned as commercialized to their IUCN Red List status and population trend, and documented geographical range and current threats (IUCN 2020). This was coupled with information on cultivation in order to be able to assess possible conservation issues for any of the Aframomum species (e.g., habitat loss, overharvesting), with the idea that the cultivation of marketable forest products relieves the pressure from wild resources (Ticktin 2004).

We visualized the results of this systematic literature review in two maps. The first map was made in R v3.6.3, with the packages “ggplot2” and “rnaturalearth”. We used the coordinates of 51 Aframomum species that were listed as human observations or preserved specimens by the Global Biodiversity Information Facility (www.gbif.org). The second map was assembled using Photopea (http://www.photopea.com). The pie chart was drawn up in Excel and bar plots were also made in R v3.6.3, using the package “ggplot2”.

Results

Sourced Publications and Selection

In total, 280 unique peer-reviewed articles, books and (conference) reports were generated through the searches in WOS, SCOPUS, Google Scholar and Prelude (Table 1). Some studies arose through multiple search engines, hence the number of publications generated through the four engines is higher than the number of combined unique publications from all four search engines.

Table 1 Number of publications generated in round one and reviewed in round two from all four search engines, including the total number of publications per round

The full text of 50 out of the total of 280 articles in round one could not be accessed through the internet or via the library staff of the four Dutch research institutes. These publications were therefore not included in our analysis. From the remaining 230 publications, 70 studies were retrieved that yielded the data used in our analysis. A complete overview of all data extracted from these references can be found in Appendix S.1. The remaining 160 publications were discarded because they did not mention the sale of at least one species of Aframomum in Africa.

Availability and Quality of Voucher Material and Commercialization Locality

Only 51 of the 62 Aframomum species reported by Harris and Wortley (2018) were listed in GBIF as herbarium vouchers and/or human observation (Fig. 2). All Aframomum species occur in the wild, but four of them are also cultivated.

Fig. 2
figure2

Map showing the localities of herbarium specimens and human observations of the 51 Aframomum species that are listed by GBIF in Africa. Coordinates obtained from GBIF.org (GBIF Occurrence Download: https://doi.org/10.15468/dl.au26mk, 22 January 2021).

Among the 70 selected publications, only 28 reported that they had produced voucher material that was deposited at an herbarium. Twelve studies collected their plant specimens from living material (either from wild or from cultivated individuals), 11 studies collected their specimens from a market, one study collected vouchers from both living material and a market and four studies did not specify where they obtained their voucher material (Fig. 3). Vouchers made from market material included whatever parts of the plants were for sale, e.g., dried fruits or seeds. Of the 28 publications that documented the creation of herbarium vouchers, seven did not report voucher numbers. The remaining 42 articles did not produce vouchers of any sort.

Fig. 3
figure3

Voucher presence and collection locality in the 70 publications that reported the commercialization of Aframomum species in Africa.

The 70 publications that were reviewed in this study yielded 15 countries with documented sales of at least one species of Aframomum: Angola, Benin, Burundi, Cameroon, Congo-Brazzaville, Democratic Republic of the Congo, Egypt, Equatorial Guinea, Ethiopia, Gabon, Ghana, Ivory Coast, Liberia, Nigeria and Sierra Leone. In total, 14 of the 62 recognized species of Aframomum were reported to be sold in these countries (Fig. 4). Additionally, there was mention of two species – A. grana-paradisi (L.) K.Schum. and A. hanburyi K.Schum. – that are no longer accepted. A. hanburyi, mentioned as sold in Equatorial Guinea and Ghana (Lock et al. 1977; Sunderland and Obama 1999), has been recognized as a synonym of A. daniellii (Hook.f.) K.Schum. and was treated as such in this review. A. grana-paradisi was mentioned in one study from Cameroon (Dibong et al. 2011). Because it is a name that represents a group of vouchers of differing species (Harris and Wortley 2018), we could not assign this specimen to a recognized species in this review.

Fig. 4
figure4

Map of Africa depicting the sale of Aframomum species per country, for the 14 commercialized species mentioned in the reviewed literature. Open circles indicate that there was at least one voucher present for every commercialized species.

The amount of documented Aframomum species for sale and the presence of vouchers for those species differed substantially between countries (Fig. 4). Most of the studies presenting data on the commercialization of Aframomum took place in Nigeria and Cameroon. These countries also yielded the highest diversity of traded species. We found 31 publications that addressed the sale of Aframomum spp. in Nigeria, mentioning five species, while 16 publications yielded information on the sale of Aframomum spp. in Cameroon, totalling 11 species. Two of the five species identifications reported from Nigeria were supported by vouchers (Fig. 5B). Among the 11 species of Aframomum documented as being sold in Cameroon, nine were based on voucher specimens (Fig. 5C). All other countries were represented by five studies or less. Eight countries (Burundi, Congo-Brazzaville, Egypt, Equatorial Guinea, Gabon, Ivory Coast, Liberia and Sierra Leone) were only represented by one study. Congo-Brazzaville, Equatorial Guinea, Ethiopia, Ivory Coast, Liberia and Sierra Leone lacked any voucher material for the species that were sold there.

Fig. 5
figure5

Number of publications mentioning the sale of different Aframomum species in: A) all 70 publications resulting from the systematic literature review; B) publications referencing the sale of Aframomum spp. in Nigeria; and C) publications referencing the sale of Aframomum spp. in Cameroon.

Among the 14 species of Aframomum that we encountered in this review, A. melegueta was most frequently mentioned as being sold on African markets (Fig. 4; Fig. 5A). The sale of A. melegueta was reported in 48 studies from 12 countries that produced 18 vouchers, followed by A. daniellii (13 mentions from four countries and four vouchers) and A. citratum K.Schum. (eight mentions from two countries and three vouchers). All other species were mentioned five times or less (Fig. 5A). Three of the 14 species of Aframomum that were identified as being sold in Africa were not supported by any vouchers: A. exscapum and A. sulcatum K.Schum. were only mentioned in one publication. A. corrorima, however, was mentioned in five studies from Ethiopia (Fig. 5A; Table S.1). These identifications were said to be based on examinations by expert botanists or were simply said to be verified at a laboratory or herbarium.

Range of Commercialized Aframomum Species

Four Aframomum species were encountered on markets outside of their natural or cultivated range (Fig. 4; Appendix S.2). A. melegueta was found to be sold in Egypt (El-Halawany et al. 2012), which is far outside of its range that stretches from Guinea to the Democratic Republic of the Congo and Angola (Appendix S.2; Harris and Wortley 2018). A. sulcatum was found to be sold in Nigeria (Ajiboye et al. 2016; Kayode et al. 2008), while this species is said not to cross the Dahomey Gap (Harris and Wortley 2018). Fruits of A. cf. longipetiolatum Koechlin were reportedly sold by Baka foragers to spice traders in southeast Cameroon (Gallois et al. 2020), even though this species is known to be endemic to Gabon (Harris and Wortley 2018). Finally, Dibong et al. (2011) mention the sale of A. exscapum – written as A. excapum – on a market in Douala, Cameroon, although according to Harris and Wortley (2018) it does not occur further east than Ivory Coast.

Conservation Status of Commercialized Aframomum Species

All but two of the 14 Aframomum species that were found to be sold in Africa are classified as Least Concern on the IUCN Red List (Table 2). All known cultivated species are classified as Least Concern, with the exception of A. melegueta, which is classified as Data Deficient because the species has been cultivated and subsequently naturalized throughout tropical Africa and its natural range can therefore no longer be established (Harris et al. 2019c). A. kayserianum is classified as Endangered, due to its restricted range and forest loss in Cameroon and Nigeria (Harris et al. 2019d). This species was reported as being sold on Cameroonian markets by a single study (Dzoyem et al. 2014).

Table 2 Red List status, population trend and cultivation data for all Aframomum species commercialized in Africa

LC = Least Concern, EN = Endangered, DD = Data Deficient.

From the species that are classified as Least Concern, A. sceptrum and A. subsericeum have decreasing population trends. The wild population trends of all other species are either stable or unknown, including those species that can be found in cultivation. Interestingly, for more than half of all species found to be sold in Africa, no data exists on their population or conservation status (Table 2).

Discussion

This systematic literature review provides relevant insights into the current knowledge on trade and conservation issues within the genus of Aframomum, and revealed extensive knowledge gaps on the taxonomic identification of the commercialized Aframomum specimens. In this study we have tried to amass all research on commercialization of Aframomum in Africa, but information may have been missed from the 50 publications of which the full text was not available online or through university libraries. We also excluded information on the commercialization of Aframomum in Africa that was mentioned on labels of herbarium specimens collected on markets that were never featured in any publication. A search through the Naturalis Bioportal (https://bioportal.naturalis.nl) yielded a specimen that was collected on a Nigerian market, but this voucher was never mentioned as such in a publication (Fig. 6). The extraction of similar label data, lying hidden in numerous digitalized and non-digitalized herbaria worldwide, would take years.

Fig. 6
figure6

A) Herbarium voucher (WAG.1201727) of dried fruits of A. melegueta from Dugbe market in Ibadan, Nigeria; B) a close-up of the label. Source: Naturalis Biodiversity Center.

Range, Commercialization and Conservation of Aframomum Spp. in Africa

Among the 14 species of Aframomum traded in 15 African countries, A. melegueta was encountered most frequently and in the most countries. This is not surprising, given that A. melegueta has been cultivated and traded internationally for centuries, thereby potentially extending its range (Harris and Wortley 2018; Lock et al. 1977; Van Harten 1966). Interestingly, two studies from Nigeria and the Democratic Republic of the Congo indicated that material of A. melegueta sold on the markets was collected from the wild (Bakwaye et al. 2013; Kayode et al. 2008). If this information from market vendors is correct, this suggests that although most material of A. melegueta sold on markets comes from cultivated individuals, this species may still be locally collected from the wild as a NTFP. This knowledge, coupled with the fact that A. melegueta was mentioned as a rare wild species in Nigeria (Olanipekun et al. 2016), indicates that local conservation issues for wild A. melegueta may be present.

Our systematic literature review also yielded three publications in which A. melegueta was labelled as an NTFP even though the material for sale was said to come from cultivated sources (Appendix S.1; Guedje et al. 1998; Ingram and Schure 2010; Towns et al. 2014). This shows that the term NTFP is not always well understood and that care should be taken when this term is encountered. Due to this confusion, it is of utmost importance to clearly separate wild-sourced and cultivated material of A. melegueta sold on markets when examining conservation threats and assessing the harvest sustainability of this species. If the commercialized material comes from cultivated individuals, the risk of overharvesting wild resources is limited, although natural Aframomum populations may still threatened by deforestation.

The second Aframomum species sold in Africa that might be experiencing conservation threats is A. kayserianum: the only commercialized species that is Endangered according to the IUCN Red List. This is due to its restricted range in Nigeria and Cameroon and possible habitat loss through agricultural development, especially on the Obudu Plateau in Nigeria (Harris et al. 2019d). Harris et al. (2019d) suggest that the high altitude at which this species occurs in Cameroon would protect it from the bulk of forest loss in that country. Moreover, Harris and Wortley (2018) state that within its range, A. kayserianum is not rare. These contradictory assessments for the different countries coupled with the fact that we only found one study documenting the sale of A. kayserianum and no additional literature on the harvest of this species, indicates that more research is needed to assess whether or not the harvest of A. kayserianum for commercial purposes in Africa is sustainable. Such a venture will have to include market surveys in and around the mountainous areas of Nigeria and Cameroon, as well as expeditions to the source material as indicated by sellers, during which the local population size can be assessed. The second- and third-most mentioned commercialized species were A. daniellii and A. citratum. They occur solely in the wild and are both widespread, although A. citratum is described in Harris and Wortley (2018) as “not very common”. Both are labelled Least Concern by the IUCN Red List, indicating that an imminent risk of decreasing populations or extinction through the harvesting of these species is unlikely.

East African Knowledge Gap

Through our literature review a major knowledge gap was revealed for the Central African Republic, Kenya, Malawi, Mozambique, Rwanda, South-Sudan, Tanzania, Togo and Uganda. These predominantly East African countries yielded no publications on the commercialization of Aframomum through the channels used in this study. Undoubtedly, market surveys on spices and medicinal plants in these countries, which all possess rainforest and savanna habitat suitable for Aframomum spp., would yield data on sales of fruits, seeds, rhizomes or leaves. Various species, such as A. corrorima and A. albiflorum Lock, are endemic to East Africa (Harris and Wortley, 2018) and market surveys in these areas thus hold the potential to significantly contribute to the knowledge of trade in Aframomum. Ethiopia was the only East African country represented by more than one publication, but this country is also in need of more research into the trade in Aframomum spp. None of the five studies from Ethiopia produced vouchers, which raises the question if A. corrorima is truly the only commercialized Aframomum species in Ethiopia. Given the fact that A. angustifolium is known to be commonly cultivated in Ethiopian home gardens (Furo et al. 2020), it would surely be found on regional markets with intensified sampling.

Species Identification Limitations

Our systematic literature review yielded important insights regarding the reliability of the species identifications of Aframomum spp. sold in Africa. Strong limitations were uncovered concerning both the availability and quality of voucher material collected in the reviewed articles. More than half of the included publications did not report the creation of any kind of voucher. Their identifications were either based on the evaluation of an (unnamed) expert, or there was no mention of how the species were identified at all. The lack of traceable voucher material, makes it impossible to verify whether the species mentioned are correctly identified. This in turn hinders the design of management plans for sustainable extraction of commercialized Aframomum species. Especially the many studies that focused on potential pharmacological properties of Aframomum species without mentioning any voucher material (e.g., Ajiboye et al. 2016) should be more careful in attributing effects to certain species, as their identification cannot be checked.

The most well-represented country, Nigeria, showed that quantity and quality do not necessarily coincide. At first sight, Nigeria seemed to be particularly well-studied. Yet, only two out of the five traded species were reported in studies that provided vouchers, thereby making species verification possible. All reported vouchers from Nigeria concerned A. melegueta except for one herbarium specimen of A. daniellii (Okeke et al. 2018). The identity of the three additional species reported to be sold in this country cannot be verified. This contrasts with our findings from Cameroon, where the species were much better represented by herbarium material. Thus, there is no clear link between the quantity of studies referencing the commercialization of Aframomum, and the quality of the species identifications within those publications.

For the 28 publications that did produce vouchers it would in theory be possible to verify their species identifications, which is important because Aframomum is frequently mis-identified in herbaria and identifications of vouchers cannot blindly be assumed to be correct (Goodwin et al. 2015). This is especially true for the vouchers from the 11 studies that used market-sourced material. These vouchers rarely contain the whole plant and the material is often already dried. An example of how such dried plant material is encountered on an African market is presented in Fig. 7. Given the fact that these parts are very difficult to identify in isolation from other tissues, identification issues can ensue when relying on morphology. This is a common problem with identifying specimens across African markets. Wares are often dried and bought from middlemen, thereby complicating species identification (Van Andel et al. 2012). In the case of Aframomum, market-sourced vouchers can be accurately re-examined by DNA barcoding of specimens that have been revised and cited in Harris and Wortley (2018), after which additional vouchers can be identified through DNA analysis.

Fig. 7
figure7

Unidentified Aframomum fruits (indicated by red square) sold as an ingredient in a pau de cabinda aphrodisiac mixture in Angola. Source: Destino Venda, Wikimedia Commons

We also encountered several publications in which the authors did state that they created vouchers but in which the voucher numbers were not reported. It is impossible to revise these without contacting the author personally, shrinking the pool of verifiable vouchers even further. In the end, only 21 publications produced vouchers and made these traceable by providing voucher numbers, and just ten of those vouchers contained the whole plant. The specimens in all other studies are either unverifiable, untraceable or possibly need DNA analysis to accurately confirm the species identification.

Conclusion and Recommendations

This study offers a first overview of the trade in Aframomum in Africa. Among the 14 commercialized species of Aframomum traded in 15 African countries, A. melegueta was encountered most frequently and Nigeria and Cameroon were studied most intensively. Conservation concerns were found for A. kayserianum and possibly for wild A. melegueta populations. Yet, large knowledge gaps exist concerning the commercialization of Aframomum in almost all East African countries within the native range of Aframomum and the majority of sourced publications did not base their species identification on herbarium vouchers. Only 13 studies collected the whole plant from the wild or place of cultivation and three of those publications never mentioned the voucher numbers. The lack of herbarium material or reported voucher numbers means that those species identifications are not verifiable. A problematic matter, given that Aframomum is often misidentified in herbaria and that Aframomum is an important yet obviously understudied income generator throughout Africa. More detailed knowledge concerning the trade in A. melegueta and A. kayserianum will be crucial to identify to what degree the collection of these species as an NTFP poses conservation threats. Given these considerable shortcomings, we recommend that future academic endeavours investigating the commercialization of Aframomum spp. in Africa focus on countries within the native range of Aframomum that have as of yet not been the subject of intensive study. Moreover, care should be taken to collect vouchers, preferably from living material that has been indicated by the vendors as the source plant of the marketed products. Voucher numbers and the herbarium where the vouchers are deposited should be reported in the publication. This will allow researchers to verify the identification through morphological studies using the new revision by Harris and Wortley (2018) or through DNA analysis. By simultaneously reporting the source of the material (either from the wild or from cultivated sources), as well as noting the abundance in the wild, future research could also effectively aid in the detection of further conservation issues surrounding commercialized species of Aframomum in Africa.

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Knippers, R.H.M., Gallois, S. & van Andel, T. Commercialization of Aframomum spp. in Africa: a Systematic Review of Literature and Supporting Botanical Vouchers. Econ Bot 75, 76–91 (2021). https://doi.org/10.1007/s12231-021-09517-4

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Keywords

  • Grains of paradise
  • Herbarium specimens
  • Melegueta pepper
  • NTFP
  • Trade
  • Wild edible plants