The steno-endemic species of genus Decalepis are highly threatened by destructive wild harvesting. The medicinally important fleshy tuberous roots of Decalepis hamiltonii are traded as substitute, to meet the international market demand of Hemidesmus indicus. In addition, the tuberous roots of all three species of Decalepis possess similar exudates and texture, which challenges the ability of conventional techniques alone to perform accurate species authentication. This study was undertaken to generate DNA barcodes that could be utilized in monitoring and curtailing the illegal trade of these endangered species. The DNA barcode reference library was developed in BOLD database platform for candidate barcodes rbcL, matK, psbA-trnH, ITS and ITS2. The average intra-specific variations (0–0.27%) were less than the distance to nearest neighbour (0.4–11.67%) with matK and ITS. Anchoring the coding region rbcL in multigene tiered approach, the combination rbcL + matK + ITS yielded 100% species resolution, using the least number of loci combinations either with PAUP or BLOG methods to support a character-based approach. Species-specific SNP position (230 bp) in the matK region that is characteristic of D. hamiltonii could be used to design specific assays, enhancing its applicability for direct use in CITES enforcement for distinguishing it from H. indicus.

Decalepis arayalpathra, a critically endangered plant species, has a restricted and fragmented population in Southern Western Ghats, India. This study is a first attempt to evaluate genetic diversity and population structure in the nine wild populations of D. arayalpathra based on molecular pattern realized through the marker assays. Principal coordinate analysis (PCoA) and Nei's unweighted pair-group method with arithmetic average (UPGMA)-based hierarchical clustering of both the marker assays suggest strong genetic clustering between the individuals corresponding to their geographical ranges. Mantel test also corroborates a close genetic proximity between genetic and geographic data (r = 0.389). Population genetic analysis revealed low levels of gene flow [inter-simple sequence repeat (ISSR) = 0.289 and random amplified polymorphic DNA (RAPD) = 0.847] between the populations, in line with high genetic differentiation (Gst = 0.531 with ISSR and 0.440 with RAPD), which was also supported by analysis of molecular variance (AMOVA), that 54 % (ISSR) and 64 % (RAPD) total variation resided within populations. Bayesian model-based STRUCTURE analysis detected three genetic clusters showing the high degree of admixture within population. Based on the findings, such as inbreeding depression and the loss of genetic diversity, suggestions for conservation strategies are provided to preserve the genetic resources of this endangered species.

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