Differentiating siliceous particulate matter in the diets of mammalian herbivores
Differentiating siliceous particulate matter in the diets of mammalian herbivores
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DOI：
10.1111/2041-210x.13934
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发表时间：
2022-07-15
影响因子：
6.6
通讯作者：
Dominy, Nathaniel J.
中科院分区：
文献类型：
--
作者：
Fannin, Luke D.;Laugier, Elise J.;Dominy, Nathaniel J.
二氧化硅对地球上的陆地植物生命和地球化学循环至关重要。它也与哺乳动物牙齿的进化有关，但关于哪种类型的硅质颗粒对牙齿形态施加了最大的选择压力，还存在争议。争论围绕植物中存在的无定形硅体(植硅体)和植物表面各种形式的硅质砂砾--即结晶石英(沙、土壤、灰尘)--展开。问题是，传统的二氧化硅测量方法往往同时对两种颗粒类型进行量化。在这里，我们描述了一种依靠重液浮选分离和量化食草动物饲料中硅质颗粒物质的方案。该方法重现性好，非常适合于检测二氧化硅摄入的物种或种群水平的差异。此外，我们在奶牛的消化道中检测到了有意义的变化，这一结果支持了瘤胃液对硅质砂砾进行“清洗”的前提。我们使用Bootstrap重采样来估计在空间和时间上比较物种、种群或个体所需的样本量。我们发现，如果物种是食草动物，至少需要12个个体，如果物种是食草动物，则需要多达55个个体，这两个物种的变量更大。但20个样本的大小足以检测统计差异。我们的结论是，我们用于区分和量化二氧化硅的方案有望测试关于牙齿特征进化的相互竞争的假说。
Silica is crucial to terrestrial plant life and geochemical cycling on Earth. It is also implicated in the evolution of mammalian teeth, but there is debate over which type of siliceous particle has exerted the strongest selective pressure on tooth morphology. Debate revolves around the amorphous silica bodies (phytoliths) present in plants and the various forms of siliceous grit-that is, crystalline quartz (sand, soil, dust)-on plant surfaces. The problem is that conventional measures of silica often quantify both particle types simultaneously. Here we describe a protocol that relies on heavy-liquid flotation to separate and quantify siliceous particulate matter in the diets of herbivores. The method is reproducible and well suited to detecting species- or population-level differences in silica ingestion. In addition, we detected meaningful variation within the digestive tracts of cows, an outcome that supports the premise of ruminal fluid 'washing' of siliceous grit. We used bootstrap resampling to estimate the sample sizes needed to compare species, populations or individuals in space and time. We found that a minimum sample of 12 individuals is necessary if the species is a browser or as many as 55 if the species is a grazer, which are more variable. But a sample size of 20 is adequate for detecting statistical differences. We conclude by suggesting that our protocol for differentiating and quantifying silica holds promise for testing competing hypotheses on the evolution of dental traits.