Dietary niche stability of equids across the mid-Miocene Climatic Optimum in Oregon, USA
Dietary niche stability of equids across the mid-Miocene Climatic Optimum in Oregon, USA
复制标题
DOI：
10.1016/j.palaeo.2015.03.012
复制
发表时间：
2015-05
期刊：
影响因子：
--
通讯作者：
Kaitlin C. Maguire
中科院分区：
文献类型：
--
作者：
Kaitlin C. Maguire
在北美中新世中期，高齿马科动物比短齿马科动物变得更加多样化和丰富。这种模式在俄勒冈州的中新世沉积物中很明显，其中短齿兽类群灭绝，而长齿象马科动物则繁盛。这种与牙齿形态差异相关的更替被认为是类群之间饮食差异的结果，高齿兽物种利用不断扩大的草原景观，而短齿兽物种的消亡则由于适合浏览的植被减少而导致。在这里，这个假设得到了检验，并使用稳定的碳和氧同位素检查了四个马科动物属的饮食生态位。根据 δ13C 和 δ18O 值以及牙齿形态，饮食生态位划分很明显：Archaeohippus（一种小型短齿马科动物）的饮食生态位很窄，很可能在林地栖息地的空地上吃冠叶植被；Parahippus 和 Desmatippus（中型短齿马科动物到早期长齿马科动物）在相对开放的环境中吃 C3 植被； aff.Acritohippus 是一种较大的高齿马科动物，具有广泛的饮食习惯，在相对开放的环境中以 C3 草为食。这四个属的饮食生态位并没有随着时间的推移或中新世中期气候最适期而改变。食草属的局部灭绝，尤其是生态位宽度狭窄的古马属，最有可能是由于中新世中期气候最适宜期后，随着 C3 草的传播，栖息地的开放。没有证据表明 aff.Acritohippus 的饮食中存在 C4 植被，这与 C4 草在中新世中期并未入侵太平洋西北地区的观点一致，与当时北美其他地区的情况相反。
During the middle Miocene in North America, hypsodont equids became more diverse and more abundant than brachydont equids. This pattern is evident in middle Miocene deposits of Oregon in which the brachydont taxa became extinct while the hypsodont equids flourished. This turnover, associated with morphological tooth differences, is hypothesized to be a result of dietary differences between taxa, with hypsodont species exploiting the increasing grassland landscape and demise of the brachydont species a result of less vegetation suitable for browsers. Here this hypothesis is tested and the dietary niches of four equid genera are examined using stable carbon and oxygen isotopes. Dietary niche partitioning is evident based on δ13C and δ18O values and tooth morphology:Archaeohippus, a small brachydont equid, had a narrow dietary niche most likely consuming crown leaf vegetation in the clearings of a woodland habitat;ParahipppusandDesmatippus, medium sized brachydont to incipiently hypsodont equids, ate C3vegetation in a relatively open environment; and aff.Acritohippus, a larger hypsodont equid, had a broad dietary niche eating C3grasses in a relatively open environment. The dietary niches of these four genera did not change through time or across the mid-Miocene Climatic Optimum. Local extinction of the browsing genera, especiallyArchaeohippuswith its narrow niche breadth, was most likely due to the opening of habitats as C3grasses spread after the mid-Miocene Climatic Optimum. There is no evidence of C4vegetation in the diet of aff.Acritohippusconsistent with the idea that C4grasses did not invade the Pacific Northwest during the middle Miocene, in contrast to other regions of North America during that time.