An integrative analysis of population genetics and species distribution modeling of Gymnema sylvestre in India

Gymnema sylvestre (Retz.) R. Br. ex Schult., is a potent anti-diabetic, tropical plant species from Africa to Australia. It has been used since centuries both in indigenous and modern medicine systems to treat diabetes, snake bite, malaria, jaundice, asthma, bronchitis, cardiopathy, leukoderma, eye problems, obesity, etc. In India, the species is significantly threatened by unsustainable harvesting practices for pharmaceutical industries and habitat destruction. Moreover, the continuing climate change may affect its distributional range. Hence, the objective of this study was to evaluate the genetic health (genetic diversity and population genetic structure) and potential geographical range of G. sylvestre under both current (1970–2000) and projected future climatic conditions (2050 and 2070 under Representative Concentration Pathway 4.5 and RCP8.5) to develop effective conservation, management, and sustainable utilization approaches. A moderate level of genetic diversity was found {Observed Heterozygosity (H_o = 0.391), Nei’s Expected Heterozygosity (H_e = 0.382), and Shannon’s information index (I = 0.656)}, with majority of the genetic variation accumulated within populations (74 %), and very high Nei’s genetic differentiation among populations (F_ST = 0.281) was noticed as the Gene flow among populations (N_m = 0.637) was medium. Various genetic clustering methods yielded two distinct (K = 2) genetic clusters in 118 G. sylvestre individuals proportionate to the geographical isolation. Compared to the present, all the future projections came pessimistically with a reduction in the high and moderate suitable areas. However, 2070 would favor the species in adaptation to the changed climate with increased suitable area compared to the year 2050.