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Three’s a charm – identification of medicinal plant species traded at Tanzanian markets using a combination of literature, molecular and morphological methods.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

In Tanzania large parts of the population rely on traditional medicine for their primary healthcare and medicinal plants are commonly traded. Several studies on medicinal plants have been performed in Tanzania, but identifying medicinal plants sold on local markets is challenging since vendors trade sterile leaves, barks and roots, which are often sold in powdered form to increase shelf life and to allow mixing on the spot. Vernacular names might match multiple scientific species or have not been linked to a scientific species or genus. To identify vouchers that lack sufficient morphological characters, literature could be used for identification or medicinal plant vendors are accompanied into the field to collect medicinal plant vouchers for morphological identification, but this is time-consuming, season-dependent and might lead to misrepresentation of the plants that are actually present at the local markets. In this study, we identify medicinal plants sold at the Dar-es-Salaam and Tanga markets using a tied approach of DNA barcoding, literature and morphology and look at cases of over- and under-differentiation. In total 873 single ingredient medicinal plants samples corresponding to 452 ethnospecies were purchased from the herbal markets in Dar-es-Salaam and Tanga. The samples were analysed using literature, morphology and matK, rbcL and nrITS barcoding. Out of the 873 market samples 661 could be identified up to at least family level using literature and morphology, and 535 yielded a DNA barcode for at least one of the three markers. Combining the three methods a total 509 identifications could be made showing a diversity of 91 plant species in 124 genera spread over 65 plant families. Out of the 212 samples that were unidentifiable based on morphology and literature, 39 could be identified up to species level, 28 up to genus level and 55 up to family level using DNA barcoding. Analysis of the market samples revealed eighty cases of over- and under-differentiation. Afzelia quanzensis Welw. (Leguminosae), Zanthoxylum spp. (Rutaceae), Allophylus spp. (Sapindaceae) and Albizia anthelmintica Brongn. (Leguminosae) were the most obvious cases of over-differentiation, since they were traded under eight to twelve vernacular names in one to five different local languages. The most obvious case of under-differentiation was mwingajini (Swahili), which matched to a variety of scientific species in five different plant families.   This study shows that using a tied approach increases the identification success of medicinal plants sold on local market and corroborates findings that DNA barcoding be successfully applied for the identification of material that is unidentifiable based on morphology and literature. Results of this study can be used as a basis for quantitative market surveys and to investigate conservation issues associated with trade in medicinal plants.

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URN: urn:nbn:se:uu:diva-355179OAI: oai:DiVA.org:uu-355179DiVA, id: diva2:1225437
Available from: 2018-06-27 Created: 2018-06-27 Last updated: 2018-06-27
In thesis
1. Markets, mixtures and molecular methods: Investigating medicinal plant and edible orchid diversity in Tanzania and Zambia
Open this publication in new window or tab >>Markets, mixtures and molecular methods: Investigating medicinal plant and edible orchid diversity in Tanzania and Zambia
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Medicinal plants are an important source of primary healthcare for many people in Tanzania. These medicinal plants are harvested from the wild, and increasing commercial trade poses a serious threat to local plant populations. Currently it is unknown which species are traded and in what amounts. Across the southwestern border in Zambia, the traditional dish chikanda has transformed from a niche product to being a mainstream delicacy. One of the main ingredients are wild-harvested orchids, and these have become depleted throughout the country as an effect of the increased trade. It is unclear which orchid species are targeted and might be at risk of overharvesting. The aims of my doctorate are to map harvest and trade of Tanzanian medicinal plants and Tanzanian and Zambian edible orchids, to investigate whether species that are traded on local markets can be identified using molecular methods such as DNA barcoding and metabarcoding and identify conservation issues arising from wild-harvesting of medicinal plants and edible orchids.

In Paper I DNA metabarcoding analysis of Tanzanian chikanda cake show the presence of 17 different orchids species belonging to the genera DisaSatyrium and Habenaria, and in Paper V the analysis of chikanda tubers sold on Zambian markets reveals that at least 16 orchid species from 6 different orchid genera are targeted in local orchid trade. Paper II describes a quantitative market survey of the non-woody, non-powdered medicinal plants sold on Kariakoo market in Dar-es-Salaam that shows that a total of 67 species are traded in an annual volume of nearly 31 tonnes of fresh and dried medicinal leaves, seeds and fruits with an estimated value of 200,000 USD. For Paper III 873 medicinal plant products were analysed using DNA barcoding, literature and morphology to determine which species are traded on the Dar-es-Salaam and Tanga markets. In total, 509 identifications could be made corresponding to 91 species, 124 genera and 65 plant families, and several cases of over- and under-differentiation were detected. Paper IV builds upon the identifications in Paper III to determine in what amount the medicinal plant species present at the local markets are traded and to investigate if commercial trade poses a threat to local plant populations. It was found that several of the most highly favored medicinal plants were perceived to becoming more difficult to obtain in the wild.

This thesis shows that DNA barcoding is a powerful rapid identification method for morphologically unidentifiable specimens. It also shows that commercialization of wild-harvested plant products threatens local plant populations, and highlights the need for conservation measures to avoid local extinction of economically and socially important plant species.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 36
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1689
Keywords
DNA barcoding, Africa, Species delimitation, Orchids, Medicinal plants
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urn:nbn:se:uu:diva-355182 (URN)978-91-513-0376-5 (ISBN)
Public defence
2018-09-13, Zootissalen, Villavägen 9, Uppsala, 09:00 (English)
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Available from: 2018-08-22 Created: 2018-06-27 Last updated: 2018-08-28Bibliographically approved

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