Comparing medicinal plant knowledge using similarity indices: A case of the Brou, Saek and Kry in Lao PDR

Medicinal plant traditional knowledge is one of the most widely known traditional ecosystem services, as it provides primary healthcare, contributes to subsistence livelihoods, and for its potential value as a source of novel pharmaceuticals. People living in close contact with their surroundings for many generations are hypothesized to have developed, through trial-and-error, in-depth knowledge of ecosystems, biodiversity, and their management and utility. In the case of medicinal plant knowledge it could lead to an asymptotic climax or a constantly evolving equilibrium of cures with proven efficacy and those under assessment. An in-depth study of 97 plant species used in traditional medicine by the Brou, Saek and Kry ethnic groups in Lao PDR was made to test similarity in medicinal plant knowledge. Medicinal plants were used in 99 different ways in 510 species-use combinations. Medicinal uses could be generalized into 12 use categories with 747 species-category combinations. Similarity indices show Brou and Saek plant use appears to be most similar (QSBS: 60.0; JIBS: 75.1) followed by Kry and Saek (QSKS: 51.6; JIKS: 53.4), and then Kry and Brou (QSBK: 46.9; JIBK: 44.1). Intercultural similarities found are quite low, considering that all three groups share the same geographical and ecological area and have the same dependence on medicinal plants. Intercultural transmission is unimpeded but many treatments are likely to be ineffective. Comparison of the similarities found here with similarities computed from other data show that these results are homologous with other sympatric ethnic groups, and much higher than those for allopatrically living groups. Medicinal plant knowledge does not reach a stable climax, but appears to evolve continually by trial-and-error, as effective cures to many ailments are unavailable.