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

As many ecosystems are under increasing pressure from invasive species, habitat degradation, overgrazing and overharvesting, pollution, and climate change, dietary niche monitoring is gaining importance. The Malai Mahadeshwara Wildlife Sanctuary (MMH) in southern India is home to several long-standing ethnic and tribal groups and supports 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 herbivores occurring in MMH using eDNA metabarcoding to quantify diet richness, composition and overlap. In total, we distinguish 134 diet items (molecular operational taxonomic units), covering 31 plant families. Overall, our results indicate 35% overlap in domestic and wild herbivore diet items. The greatest overlap is found for the dietary niches of cattle and sambar deer (Pianka's niche overlap index: 0.68), and the dietary niche of cattle also overlaps considerably with those of Indian hare (0.65) and Asian elephant (0.46). This suggests that these herbivores may compete for these food plants in the case of limited availability, which could lead to exclusion of some herbivore species. Particular concern should go to bonnet macaque and Asian elephant as their below average dietary richness could make them vulnerable to changes in their environment. With increasing pressures on local wildlife from a range of different factors, DNA metabarcoding of faecal samples is a non-invasive method for monitoring changes in animal diets, providing valuable information for the management of biodiversity in mosaic natural and anthropogenic landscapes.

随着全球诸多生态系统正面临外来入侵物种、生境退化、过度放牧、过度采伐、污染以及气候变化带来的日益加剧的压力，饮食生态位监测的重要性愈发凸显。印度南部的迈莱·马哈德什瓦拉野生动物保护区（Malai Mahadeshwara Wildlife Sanctuary, MMH）境内聚居着多个历史悠久的族群与部落，同时承载着相当数量的家养草食动物（牛、山羊与水牛）以及多种野生动物，包括多种鹿类、帽猴（bonnet macaque）与亚洲象。本研究采用环境DNA元条形码（environmental DNA metabarcoding）技术，对该保护区内草食动物的饮食生态位分化模式进行了重构，以量化其饮食丰富度、组成及重叠程度。本研究共识别出134种饮食项（分子操作分类单元（molecular operational taxonomic units, MOTU）），涵盖31个植物科。整体而言，研究结果显示家养与野生草食动物的饮食项重叠率达35%。其中，牛与水鹿的饮食生态位重叠度最高（皮安卡生态位重叠指数（Pianka's niche overlap index）：0.68）；牛的饮食生态位还与印度野兔（0.65）及亚洲象（0.46）存在较高程度的重叠。这表明在食物资源匮乏的情境下，这些草食动物可能会为食用植物产生竞争，进而可能导致部分草食动物物种被排挤。应格外关注帽猴与亚洲象，因其饮食丰富度低于平均水平，易受环境变化影响。面对多种因素给当地野生动物带来的持续压力，粪便样本的环境DNA元条形码技术是一种非侵入性的动物饮食变化监测方法，可为镶嵌式自然与人工复合景观中的生物多样性管理提供极具价值的参考信息。