Abstract
Reptiles are key components of modern ecosystems, yet for many species detailed characterisations of their diets are lacking. Data currently used in dietary reconstructions are limited either to the last few meals or to proxy records of average diet over temporal scales of months to years, providing only coarse indications of trophic level(s). Proxies that record information over weeks to months would allow more accurate reconstructions of reptile diets and better predictions of how ecosystems might respond to global change drivers. Here, we apply dental microwear textural analysis (DMTA) to dietary guilds encompassing both archosaurian and lepidosaurian reptiles, demonstrating its value as a tool for characterising diets over temporal scales of weeks to months. DMTA, involving analysis of the three-dimensional, sub-micrometre scale textures created on tooth surfaces by interactions with food, reveals that the teeth of reptiles with diets dominated by invertebrates, particularly invertebrates with hard exoskeletons (e.g. beetles and snails), exhibit rougher microwear textures than reptiles with vertebrate-dominated diets. Teeth of fish-feeding reptiles exhibit the smoothest textures of all guilds. These results demonstrate the efficacy of DMTA as a dietary proxy in taxa from across the phylogenetic range of extant reptiles. This method is applicable to extant taxa (living or museum specimens) and extinct reptiles, providing new insights into past, present and future ecosystems.
Highlights
Extant reptiles include lepidosaurs, archosaurs and chelonians
Principal Component Analysis (PCA) of these four parameters separates reptile guilds in a multivariate texture-dietary space, defined by principal component axes 1 and 2, which together account for 91.3% of the total variance (Fig. 2)
This study provides the first evidence that microwear textures on non-occlusal tooth surfaces in reptile dietary guilds that encompass archosaurs and lepidosaurs track dietary differences and differ between guilds
Summary
Extant reptiles include lepidosaurs (lizards, snakes and tuataras), archosaurs (crocodilians) and chelonians (turtles and tortoises). DMTA is potentially applicable to reptiles, but they differ in a number of significant ways from mammals: (i) their teeth are routinely shed[44]; (ii) dentitions are typically non-occlusal; (iii) food processing is less (reptiles commonly swallow entire food items or crudely tearing them into pieces45,46); (iv) they have lower energy requirements because of their ectothermic metabolism[47] and consume less These characteristics limit the frequency and duration of tooth-food interactions in reptiles, relative to those of mammals, and differences in microwear textures between reptiles with different diets are likely to be more subtle and to reflect diet over longer temporal scales. Until the hypothesis that microwear tracks diet has been tested, DMTA cannot be considered as a reliable proxy for dietary reconstruction in non-lepidosaur reptiles
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