Another one bites the dust: Faecal silica levels in large herbivores correlate with high-crowned teeth

Institut für Tierwissenschaften, Universität Bonn, Bonn, Germany.
Proceedings of the Royal Society B: Biological Sciences (Impact Factor: 5.05). 11/2010; 278(1712):1742-7. DOI: 10.1098/rspb.2010.1939
Source: PubMed


The circumstances of the evolution of hypsodonty (= high-crowned teeth) are a bone of contention. Hypsodonty is usually linked to diet abrasiveness, either from siliceous phytoliths (monocotyledons) or from grit (dusty environments). However, any empirical quantitative approach testing the relation of ingested silica and hypsodonty is lacking. In this study, faecal silica content was quantified as acid detergent insoluble ash and used as proxy for silica ingested by large African herbivores of different digestive types, feeding strategies and hypsodonty levels. Separate sample sets were used for the dry (n = 15 species) and wet (n = 13 species) season. Average faecal silica contents were 17-46 g kg(-1) dry matter (DM) for browsing and 52-163 g kg(-1) DM for grazing herbivores. No difference was detected between the wet (97.5 ± 14.4 g kg(-1) DM) and dry season (93.5 ± 13.7 g kg(-1) DM) faecal silica. In a phylogenetically controlled analysis, a strong positive correlation (dry season r = 0.80, p < 0.0005; wet season r = 0.74, p < 0.005) was found between hypsodonty index and faecal silica levels. While surprisingly our results do not indicate major seasonal changes in silica ingested, the correlation of faecal silica and hypsodonty supports a scenario of a dominant role of abrasive silica in the evolution of high-crowned teeth.

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    • "With respect to endogenous sources of wear, silica phytoliths in plant foods are commonly mentioned materials within herbivorous foods that could accelerate tooth wear and lead to early dental senescence. In particular, herbivorous species encounter higher wear rates when they ingest a higher percentage of endogenous dietary silica, and in turn have higher cheek-tooth tooth crowns (as measured by the hypsodonty index) (Hummel et al., 2011). As silica phytoliths are generally more abundant (as a percentage of dry weight) in grasses than in browse (Piperno, 1988; Hodson et al., 2005), this result has been interpreted as a dietary signal for grass eating. "
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    • "ce of a third grazing route in our data , although our results do not refute this hypothesis either . Our data suggest the buffalo is convergent on the second route to grazing and that it consumes vegetation with relatively less abrasive particles than grazing route one . This result is at odds with faecal analyses of silica levels in S . caffer ( Hummel et al . 2011 ) , which found that this species ingested high levels of silica both in wet and dry seasons , perhaps attesting to variability in the diet of this species . In the long - term evolutionary context , bovid lineages adapted to grazing in open habitats ( e . g . Alcelaphines ) are characterized by remarkable turnover ( speciation and exti"
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    • "However , complicating the picture is that plants produce a type of non-crystalline silica, usually as small separate particles, called phytoliths, which are thought to provide a form of mechanical defence (Piperno 2006). Silica levels in faeces correlate with the degree of hypsodonty in herbivores (Hummel et al. 2011), with the quantity of silica from soil outstripping that from phytoliths , at least in grazers (Damuth & Janis 2011). Quartz in soil can definitely abrade tooth enamel (remove tissue), while phytoliths from plants appear not to be able to do so (Lucas et al. 2013). "

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