Simple Nested Allele-Specific approach with penultimate mismatch for precise species and sex identification of tiger and leopard.

Abstract

Accurate species and sex identification of non-invasive and forensic samples of the tiger and leopard is still confusing when using the allele-specific methods. We designed allele-specific methods with penultimate nucleotide mismatch in a nested manner for the exact identification and double-checking of forensic samples. The mismatch design is a novel concept in species and sex identification, making the allele-specific targeting precise. We developed three sets of markers, a 365bp outer and a 98bp inner marker for nested tiger species identification assay, 136bp leopard specific marker, and carnivore sex identification markers. We validated the method with tissue/blood forensic samples of various felids and herbivorous available in our lab and on known fecal samples from Vandalur Zoo. We also collected 37 scat samples at diverse stages of deterioration from the Mudumalai Tiger Reserve, Tamil Nadu, India. The 365bp targeted markers resulted in 70.2% (n = 22; 22/37) amplification success, while the 98bp FAM-labelled marker amplified 89% (n=33; 33/37) scat samples independently. The 136bp leopard markers answered four scat samples (11%) unrequited by the tiger specific markers. We evaluated species and the sex identification with these markers in another 190 non-invasive samples provided by the Mudumalai Tiger Reserve authorities. Among which 56.3% (n= 107) of samples were recognized as tiger (64 male and 43 female) and 38.9% (n= 74) as leopard (41 male and 33 female). The method supersedes any other previous methods in this regard by its high accuracy and simplicity.