Conservation genetics of endangered Trillium govanianum Wall. ex D. Don – A pharmaceutically prized medicinal plant from the Himalaya and implications for species recovery

Abstract

Understanding the genetic diversity and population structure of pharmaceutically important endangered plant species is crucial for their conservation and sustainable use. Despite the continuous population decline in Trillium govanianum Wall. ex D. Don, a highly prized medicinal plant endemic to the Himalaya, information regarding its conservation genetics has been lacking. Here, we employed a conservation genetics approach to investigate how drastically declining populations in natural habitats impact population genetic diversity and structure of this endangered species across the Kashmir Himalaya. We used Start codon targeted (SCoT) and Simple sequence repeat (SSR) markers to assess the intra- and inter-population genetic variation in seven sites across the study region. Based on these markers, we found a very low genetic diversity in T. govanianum populations. Very low levels of observed heterozygosity (Ho = 0.000) and that expected (He = 0.064) in the populations indicate high heterozygote deficiency and high levels of inbreeding depression (FIS = 1.000). A high genetic differentiation was observed among the populations for both SCoT (Gst = 0.719) and SSR (Fst = 0.707) markers. Both the markers showed low gene flow, SCoT (Nm = 0.195) and SSR (Nm = 0.119), depicting high among-population variation than within-population variation. Analysis of molecular variance also indicated a higher genetic variation between the populations than within populations. We also observed a significant positive correlation between genetic divergence and geographical distance, indicating that genetic differentiation in T. govanianum follows a pattern of isolation by distance. Bayesian structure and cluster analysis grouped the populations according to their geographical proximity. Further, redundancy analysis (RDA) revealed the presence of one polymorphic locus for each marker with high discriminatory power. Overall, our findings reveal a very low genetic diversity, high levels of inbreeding, and high genetic differentiation among the populations; likely resulting from habitat fragmentation, population isolation, bottleneck effect, low gene flow, and predominantly asexual reproduction currently operative in the species. Finally, based on the insights gained, we discuss the potential implications of our findings in guiding species recovery and habitat rehabilitation of T. govanianum in the Himalaya with conservation lessons for elsewhere in the world.