Abstract
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.
Highlights
Living herbivorous ungulates show distinct feeding styles, which can be classified into three categories: grazers that predominantly consume graminoids, browsers that consume leaves of dicotyledons and/or fruits, and intermediate feeders that vary their diet between grazers and browsers [1]
Interspecific comparisons of extant ungulates have revealed that both phytoliths in grass and external abrasive matter may play important roles
From analysis of extant sika deer inhabiting various environments and consuming graminoids in varying proportions, notably the northern sika deer ‘‘forest grazers,’’ we quantitatively evaluated the effect of graminoid consumption on mesowear score (MS), the molar wear rate, and the M3 hypsodonty index
Summary
Living herbivorous ungulates (hooved animals) show distinct feeding styles, which can be classified into three categories: grazers that predominantly consume graminoids, browsers that consume leaves of dicotyledons and/or fruits, and intermediate (or mixed) feeders that vary their diet between grazers and browsers [1]. Because graminoids contain more phytoliths (silica) than browses [5] and because plants growing in open and dry environments are adhered by soil and grit more often than those growing in closed and wet environments [6], grazers and/or species in open habitats may ingest more abrasive matter than browsers and/or species in closed habitats [7]. There has been a long debate on which abrasive matter (i.e., intrinsic silica or extrinsic grit) plays a more prominent role in tooth wear [4,7,8,9,10,11,12], though the role of phytoliths has been challenged by recent experimental studies [9,12].
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