The catastrophic loss of large‐bodied mammals during the terminal Pleistocene likely led to cascading effects within communities. While the extinction of the top consumers probably expanded the resources available to survivors of all body sizes, little work has focused on the responses of the smallest mammals. Here, we use a detailed fossil record from the southwestern United States to examine the response of the hispid cotton rat Sigmodon hispidus to biodiversity loss and climatic change over the late Quaternary. In particular, we focus on changes in diet and body size. We characterize diet through carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope analysis of bone collagen in fossil jaws and body size through measurement of fossil teeth; the abundance of material allows us to examine population level responses at millennial scale for the past 16 ka. Sigmodon was not present at the cave during the full glacial, first appearing at ~16 ka after ice sheets were in retreat. It remained relatively rare until ~12 ka when warming temperatures allowed it to expand its species range northward. We find variation in both diet and body size of Sigmodon hispidus over time: the average body size of the population varied by ~20% (90–110 g) and mean δ¹³C and δ¹⁵N values ranged between −13.5 to −16.5‰ and 5.5 to 7.4‰ respectively. A state–space model suggested changes in mass were influenced by diet, maximum temperature and community structure, while the modest changes in diet were most influenced by community structure. Sigmodon maintained a fairly similar dietary niche over time despite contemporaneous changes in climate and herbivore community composition that followed the megafauna extinction. Broadly, our results suggest that small mammals may be as sensitive to shifts in local biotic interactions within their ecosystem as they are to changes in climate and large‐scale biodiversity loss.

中文翻译：

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更新世晚期巨型动物灭绝后，小型食草哺乳动物（粗毛棉鼠，Sigmodon hispidus）的饮食和体型发生变化

更新世末期大型哺乳动物的灾难性丧失可能导致社区内的级联效应。虽然顶级消费者的灭绝可能扩大了所有体型幸存者可用的资源，但很少有工作关注最小哺乳动物的反应。在这里，我们使用来自美国西南部的详细化石记录来检查硬毛棉鼠 Sigmodon hispidus 对晚第四纪生物多样性丧失和气候变化的反应。我们特别关注饮食和体型的变化。我们通过对化石颌骨骨胶原的碳 (δ¹³C) 和氮 (δ¹⁵N) 同位素分析来表征饮食，并通过测量化石牙齿来表征体型；丰富的材料使我们能够检查过去 16 ka 千禧年规模的人口水平反应。在全冰期期间，Sigmodon 不存在于洞穴中，在冰盖退缩后首次出现在约 16 ka。它一直相对罕见，直到大约 12 ka，当时气温升高使其能够向北扩展其物种范围。我们发现 Sigmodon hispidus 的饮食和体型随时间发生变化：种群的平均体型变化约 20% (90-110 g)，平均 δ¹³C 和 δ¹⁵N 值介于 -13.5 到 -16.5‰ 和 5.5 到分别为7.4‰。状态空间模型表明，质量的变化受饮食、最高温度和群落结构的影响，而饮食的适度变化受群落结构的影响最大。尽管巨型动物灭绝后气候和食草动物群落组成发生了同期变化，但 Sigmodon 随着时间的推移保持了相当相似的饮食生态位。宽广地，