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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Available from: Karl-Heinz Südekum, Oct 10, 2015
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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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    ABSTRACT: Objectives: Two factors have been considered important contributors to tooth wear: dietary abrasives in plant foods themselves and mineral particles adhering to ingested food. Each factor limits the functional life of teeth. Cross-population studies of wear rates in a single species living in different habitats may point to the relative contributions of each factor. Materials and methods: We examine macroscopic dental wear in populations of Alouatta palliata (Gray, 1849) from Costa Rica (115 specimens), Panama (19), and Nicaragua (56). The sites differ in mean annual precipitation, with the Panamanian sites receiving more than twice the precipitation of those in Costa Rica or Nicaragua (∼3,500 mm vs. ∼1,500 mm). Additionally, many of the Nicaraguan specimens were collected downwind of active plinian volcanoes. Molar wear is expressed as the ratio of exposed dentin area to tooth area; premolar wear was scored using a ranking system. Results: Despite substantial variation in environmental variables and the added presence of ash in some environments, molar wear rates do not differ significantly among the populations. Premolar wear, however, is greater in individuals collected downwind from active volcanoes compared with those living in environments that did not experience ash-fall. Discussion: Volcanic ash seems to be an important contributor to anterior tooth wear but less so in molar wear. That wear is not found uniformly across the tooth row may be related to malformation in the premolars due to fluorosis. A surge of fluoride accompanying the volcanic ash may differentially affect the premolars as the molars fully mineralize early in the life of Alouatta. Am J Phys Anthropol, 2015. © 2015 Wiley Periodicals, Inc.
    American Journal of Physical Anthropology 10/2015; DOI:10.1002/ajpa.22877 · 2.38 Impact Factor
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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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    ABSTRACT: Understanding the evolutionary history of the herbivore niche within African bovids has traditionally relied on examining anatomical adaptations to diet, particularly those related to digestive strategy. More recently, mesowear and stable isotope analyses have been used to great effect to reconstruct dietary preferences. We use these dietary proxies to construct a morphology-free dietary ecospace and examine the topology of the phylogenetic rela-tionships of African bovids mapped onto this ecospace. The reconstructed dietary ecospace provides evidence for four distinct dietary classes: species with C3-or C4-dominated diets that produce low or high occlusal relief, likely related to diets high or low in abrasives, respectively. We detected no evidence for a discrete mixed feeder category; the species often categorized as such represent the end members of groups of species with either C3-or C4-dominated diets. Our analysis reveals high variability within the C4 grazing ecospace, and phylogenetic evidence indicates at least two pathways to grazing, likely related to the abrasive qualities of ingested food, which may be determined by the moisture content or the height of consumed grasses. These different pathways probably contribute to the high diversity of African grazers, both today and in the fossil record. C3 browsers (non-frugivores) also display a high degree of variation, but there are no species associated with highly abrasive diets and there is evidence for only a single evolutionary pathway. We find evidence for only one evolutionary route towards frugivory, which includes species with diets that produce both high and low occlusal reliefs. The cause of abrasive wear in frugivores may be related to grit and/or the hard parts of fruits, but this requires further examination.
    Journal of Zoological Systematics and Evolutionary Research 08/2014; 53(2). DOI:10.1111/jzs.12080 · 1.68 Impact Factor
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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). "
    Annales Zoologici Fennici 04/2014; 51:143-152. · 0.86 Impact Factor
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