Prairie grass phytolith hardness and the evolution of ungulate hypsodonty
Prairie grass phytolith hardness and the evolution of ungulate hypsodonty
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DOI：
10.1080/08912963.2013.841155
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发表时间：
2014-12-01
影响因子：
1.4
通讯作者：
Erickson, Kayley L.
中科院分区：
文献类型：
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作者：
Erickson, Kayley L.
草中的硅质植硅体被认为是一种防御机制，通过引起过度的牙齿磨损来对抗放牧有蹄类动物。据推测，它们有助于这些动物的高齿进化。然而，有些人质疑草植硅体是否会磨损釉质。在这里，对蓝禾本科草（Bouteloua gracilis）进行莫氏硬度测试以确定植硅体硬度。对马和美国野牛磨牙进行微压痕，以建立牙齿组成硬度值。为了推断植硅体的耐磨性，硬度值进行了对比。植硅体硬度范围为18.0 ~ 191.5HV。这比有蹄类动物的釉质（332.6 - 363.4HV）软得多，但比其他牙齿成分硬。虽然蓝格拉玛植硅体不能直接磨损釉质，当与植硅体硬度的其他数据结合起来看，有相当大的差异，在草种和一些植硅体实际上比有蹄类釉质更难。蓝色格兰玛草植硅体甚至可能促进牙釉质磨损，这是由于较软组织的衰退造成的压力加重。鉴于这些发现和考虑，植硅体在草和食草有蹄类动物的共同进化中发挥了不可或缺的作用，尽管需要更多的测试来证明这一点。
Silica phytoliths in grasses are thought to serve as a defence mechanism against grazing ungulates by causing excessive tooth wear. It is posited that they contributed to the evolution of hypsodonty in these animals. However, some have questioned whether grass phytoliths can abrade enamel. Here Mohs hardness testing was conducted on Blue Grama grass (Bouteloua gracilis) to determine phytolith hardness. Microindentation was performed on horse and American bison molars to establish dental constituent hardness values. To infer the phytoliths' abrasion capacity, the hardness values were contrasted. Phytolith hardness ranged from 18.0 to 191.5HV. This is considerably softer than the values obtained for ungulate enamel, which range from 332.6 to 363.4HV, but harder than the other dental constituents. Although Blue Grama phytoliths are incapable of directly abrading enamel, when viewed in conjunction with other data on phytolith hardness, there is considerable variation across grass species and some phytoliths are actually harder than ungulate enamel. Blue Grama grass phytoliths may even promote enamel wear due to pressure accentuation caused by the recession of softer tissues. Given these findings and considerations, it is plausible phytoliths served an integral role in the co-evolution of grasses and herbivorous ungulates, although more testing is needed to bear this out.