eDNA metabarcoding reveals dietary niche overlap among herbivores in an Indian wildlife sanctuary

As many ecosystems are under increasing pressure from invasive species, habitatdegradation, overgrazing and overharvesting, pollution, and climate change, dietaryniche monitoring is gaining importance. The Malai Mahadeshwara Wildlife Sanctuary(MMH) in southern India is home to several long-standing ethnic and tribal groups andsupports a considerable number of domestic herbivores (cattle, goats and water buffalo)as well as a range of wildlife (including several species of deer, bonnet macaque,and Asian elephant). We reconstructed dietary niche partitioning of the herbivoresoccurring in MMH using eDNA metabarcoding to quantify diet richness, composition,and overlap. In total, we distinguish 134 diet items (molecular operational taxonomicunits), covering 31 plant families. Overall, our results indicate 35% overlap indomestic and wild herbivore diet items. The greatest overlap is found for the dietaryniches of cattle and sambar deer (Pianka's niche overlap index: 0.68), and the dietaryniche of cattle also overlaps considerably with those of Indian hare (0.65) and Asianelephant (0.46). This suggests that these herbivores may compete for these foodplants in the case of limited availability, which could lead to exclusion of some herbivorespecies. Particular concern should go to bonnet macaque and Asian elephant astheir below average dietary richness could make them vulnerable to changes in theirenvironment. With increasing pressures on local wildlife from a range of differentfactors, DNA metabarcoding of fecal samples is a non-invasive method for monitoringchanges in animal diets, providing valuable information for the management ofbiodiversity in mosaic natural and anthropogenic landscapes.