Application of Diversity Indices to Appraise Plant Availability in the Traditional Medicinal Markets of Johannesburg, South Africa

Abstract

The lack of scientific rigour in analysing ethnobotanical surveys has prompted researchers to investigate ways of quantitatively describing their data, including the use of ecological diversity indices. There are numerous indices and measures available to describe sample diversity. Twenty-two measures of species richness, diversity and evenness were reviewed using six sets of ethnomedicinal data derived from 50 formal muti shop traders (of different ethnicities) and 100 informal street traders of traditional medicine in Johannesburg, South Africa, and a seventh data set from traders on the western boundary of the Kruger National Park, South Africa. The diversity measures were coupled with species accumulation curves to construct cumulative diversity curves used to determine the minimum viable sample size on which a diversity index should be based, and to better understand the differences in the relative diversities of the samples. Distinct differences in the relative abundance and diversity of plants sold by street traders and shop traders were evident. Species diversity and evenness was found to be higher in shops, thus resulting in a lower dominance in the sale of certain plant species compared to the street traders. A survey of an informal market should include no less than 35 research participants compared to no less than 20 for the muti shops. The use of selected indices of species richness (Margalef's), diversity (Shannon, Simpson's, Fisher's alpha, Hill's numbers) and evenness are recommended as a means of describing patterns exhibited within ethnobotanical data.

Ethnobotany of rural people from the boundaries of Carlos Botelho State Park, São Paulo State, Brazil

“…Diversity -A highest plant diversity was cited for plants from type A habitats (well-preserved forest), when compared to type B (old successional forest) and types C + D (recently disturbed areas). Using rarefaction curves (Magurran 1988;Begossi 1996;Williams et al 2005), we observe that for the same number of interviews, there is a higher number of expected species from well preserved forest, followed by recently disturbed environments and old successional vegetation (Fig. 3).…”

“…Hill's diversity numbers were used to compare proportions of rare, intermediate and common species (Magurran 1988;Williams et al 2005). Hill's numbers provide a method to describe the relationship between diversity indices (Magurran 1988) and, according to Williams et al (2005), the values of N1 (ShannonWiener, base e), N2 (reciprocal of Simpson's index, 1/D) and N∞(reciprocal of the proportional abundance of the commonest species, or reciprocal of BergerParker index), corresponding to measures of abundant, very abundant, and most abundant species in a sample, respectively.…”

“…Hill's numbers provide a method to describe the relationship between diversity indices (Magurran 1988) and, according to Williams et al (2005), the values of N1 (ShannonWiener, base e), N2 (reciprocal of Simpson's index, 1/D) and N∞(reciprocal of the proportional abundance of the commonest species, or reciprocal of BergerParker index), corresponding to measures of abundant, very abundant, and most abundant species in a sample, respectively. The value of N∞can be interpreted as a measure of the common species, N1-N∞can be interpreted as a measure of the number of intermediate species, and N0-N1 corresponds to a measure of rare ones.…”

“…4). Following Williams et al (2005), in the markets of Johannesburg, the number of species represented by N2 and N∞ (common species) are indicators of the number of ethnospecies that are candidates for more immediate conservation action, reflecting the commonness or dominance of the species in the sample. In the region of Carlos Botelho State Park, we identified 42 common species from habitat A, the same number from habitat B, and 55 common species from habitats C+D.…”

“…According to these criteria, it is possible to set priorities for a group of species for conservation purposes, including C. phaea ( known by the local inhabitants, as well as having an area of occurrence that includes type A habitats, or well preserved forests. Some tree species can be considered as priority for conservation purposes, according to commonness amongst the interviewees, following the criteria of Williams et al (2005). However, as stressed by Casagrande (2004), we should avoid the danger to conservation strategies of treating knowledge as synonymous with use and cultural importance.…”