Kubo Mugino Ozaki, Yamada Eisuke
The University Museum, The University of Tokyo, Tokyo, Japan.
Department of Earth and Environmental Science, Graduate School of Science and Engineering, Kagoshima University, Kagoshima, Japan.
PLoS One. 2014 Mar 6;9(6):e90745. doi: 10.1371/journal.pone.0090745. eCollection 2014.
In reference to the evolutionary trend of increasing cheek tooth height in herbivorous ungulates, the causes of dental abrasion have long been debated. Interspecific comparisons of extant ungulates have revealed that both phytoliths in grass and external abrasive matter may play important roles. Using analysis of extant sika deer living in various environments and showing continuous latitudinal variation in food habits from northern grazing to southern browsing, we quantitatively evaluated the influence of dietary and environmental properties on three dental variables: mesowear score (MS), molar wear rate, and M3 hypsodonty index. We used 547 skulls and 740 mandibles from 16 populations of sika deer to obtain the dental measurements. We found that only graminoid proportion in diet correlated with MS and the molar wear rate, implying that phytoliths in grass abrade dental tissues. In contrast, annual precipitation in habitat was not correlated with any of the dental variables. We also found a significant correlation between the molar wear rate (selective pressure for high-crowned molars) and the M3 hypsodonty index of extant sika deer, implying an evolutionary increment in molar height corresponding to the molar wear rate. Our intraspecific comparative analyses provide further support for use of mesowear analysis as a paleodiet estimation method; it not only reveals staple food types (graminoids or dicots) but also implies regional or seasonal variation in the diet of the species.
关于食草有蹄类动物颊齿高度增加的进化趋势，牙齿磨损的原因长期以来一直存在争议。对现存有蹄类动物的种间比较表明，草中的植硅体和外部磨蚀物质可能都起着重要作用。通过对生活在不同环境中、饮食习惯从北方放牧到南方啃食呈现连续纬度变化的现存梅花鹿进行分析，我们定量评估了饮食和环境特性对三个牙齿变量的影响：中磨损评分（MS）、臼齿磨损率和M3高冠指数。我们使用了来自16个梅花鹿种群的547个头骨和740个下颌骨来获取牙齿测量数据。我们发现，只有饮食中的禾本科植物比例与MS和臼齿磨损率相关，这意味着草中的植硅体磨损牙齿组织。相比之下，栖息地的年降水量与任何牙齿变量均无关联。我们还发现现存梅花鹿的臼齿磨损率（高冠臼齿的选择压力）与M3高冠指数之间存在显著相关性，这意味着臼齿高度的进化增加与臼齿磨损率相对应。我们的种内比较分析为将中磨损分析用作古饮食估计方法提供了进一步支持；它不仅揭示了主要食物类型（禾本科植物或双子叶植物），还暗示了该物种饮食的区域或季节变化。
