Table 1 Ethnobotanical indices used for measuring informant’s medicinal plant knowledge in the Mahafaly region of SW-Madagascar

Diversity of medicinal plant use (D)

D = 1/∑ Pi², where Pi² is equal to the number of times a species was mentioned by informant ‘i’ divided by the total number of informants answer.

Simpson’s Reciprocal Index [32], adapted by [33]. Measures how many medicinal plant species an informant uses and how evenly his uses are distributed among the species.

Species use value (UV _S )

UV_S = ∑ UV_is/n_i, where UV_is is the sum of the total number of use citations by all informants for a given species and ni is the total number of informants.

Evaluates the relative importance of each plant species based on its relative use among informants [34], adapted by [35].

Family use value (FUV)

FUV = ∑UV_s/n_s, where ∑UV_S is the sum of species use value (UVs) within a family and n_s the number of species within a family.

Evaluates the use importance of a given plant family [34].