Climatic warming and the future of bison as grazers

Climatic warming is likely to exacerbate nutritional stress and reduce weight gain in large mammalian herbivores by reducing plant nutritional quality. Yet accurate predictions of the effects of climatic warming on herbivores are limited by a poor understanding of how herbivore diet varies along climate gradients. We utilized DNA metabarcoding to reconstruct seasonal variation in the diet of North American bison (Bison bison) in two grasslands that differ in mean annual temperature by 6 °C. Here, we show that associated with greater nutritional stress in warmer climates, bison consistently consumed fewer graminoids and more shrubs and forbs, i.e. eudicots. Bison in the warmer grassland consumed a lower proportion of C3 grass, but not a greater proportion of C4 grass. Instead, bison diet in the warmer grassland had a greater proportion of N2-fixing eudicots, regularly comprising >60% of their protein intake in spring and fall. Although bison have been considered strict grazers, as cli...

气候变暖或通过降低植物营养品质，加剧大型哺乳动物植食动物的营养胁迫并抑制其体重增长。然而，由于对植食动物的饮食如何随气候梯度变化的认知不足，准确预测气候变暖对植食动物的影响仍受限制。本研究利用DNA宏条形码（DNA metabarcoding）技术，重建了年均温差达6℃的两处北美野牛（Bison bison）栖息草原的饮食季节变化特征。研究结果显示，在气候更温暖的生境中，野牛面临的营养胁迫更强，其饮食中禾本科草本植物占比持续降低，而灌木与非禾本科草本（即真双子叶植物）占比升高。温暖草原中的野牛摄入的C3草本占比更低，但C4草本占比并未升高。与之相反，温暖草原中野牛的饮食含有更高比例的固氮真双子叶植物，其在春季和秋季的蛋白质摄入占比通常超过60%。尽管此前学界曾将野牛视为严格的草食性动物，但随着气候...