Abstract

In the absence of independent observational data, ecologists and paleoecologists use proxies for the Eltonian niches of species (i.e., the resource or dietary axes of the niche). Some dietary proxies exploit the fact that mammalian teeth experience wear during mastication, due to both tooth‐on‐tooth and food‐on‐tooth interactions. The distribution and types of wear detectible at micro‐ and macroscales are highly correlated with the resource preferences of individuals and, in turn, species. Because methods that quantify the distribution of tooth wear (i.e., analytical tooth wear methods) do so by direct observation of facets and marks on the teeth of individual animals, dietary inferences derived from them are thought to be independent of the clade to which individuals belong. However, an assumption of clade or phylogenetic independence when making species‐level dietary inferences may be misleading if phylogenetic niche conservatism is widespread among mammals. Herein, we test for phylogenetic signal in data from numerous analytical tooth wear studies, incorporating macrowear (i.e., mesowear) and microwear (i.e., low‐magnification microwear and dental microwear texture analysis). Using two measures of phylogenetic signal, heritability (H 2) and Pagel's λ, we find that analytical tooth wear data are not independent of phylogeny and failing to account for such nonindependence leads to overestimation of discriminability among species with different dietary preferences. We suggest that morphological traits inherited from ancestral clades (e.g., tooth shape) influence the ways in which the teeth wear during mastication and constrain the foods individuals of a species can effectively exploit. We do not suggest that tooth wear is simply phylogeny in disguise; the tooth wear of individuals and species likely varies within some range that is set by morphological constraints. We therefore recommend the use of phylogenetic comparative methods in studies of mammalian tooth wear, whenever possible.

Highlights

  • The niche of a species is formally defined as the n-­dimensional hypervolume that encompasses the set of biotic and abiotic conditions in which they live (Hutchinson, 1957)

  • Tooth wear is known to reflect everything from the lifetime diet to the last few meals of individual animals and is thought to vary on relatively short timescales (Davis & Pineda-­Munoz, 2016; Teaford & Oyen, 1989); tooth wear shows change throughout the lifetime of individuals as well as variation among individuals, and different populations within species (DeSantis et al, 2009; Fortelius et al, 2002; Rivals & Semprebon, 2006; Scott et al, 2005)

  • If tooth wear proxies are reliable reflections of average species’ diets, as many studies suggest they are (Donohue et al, 2013; Fortelius & Solounias, 2000; Fraser & Theodor, 2011; Haupt et al, 2013; Hedberg & DeSantis, 2017; Semprebon et al, 2004; Solounias & Semprebon, 2002), logic would dictate that they must show a similar degree of phylogenetic signal

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Summary

| INTRODUCTION

The niche of a species is formally defined as the n-­dimensional hypervolume that encompasses the set of biotic and abiotic conditions in which they live (Hutchinson, 1957). The most widely employed methods for dietary inference include mesowear, the visual scoring of macroscopic tooth wear (Fortelius & Solounias, 2000; Fraser et al, 2014; Kaiser & Fortelius, 2003; Kaiser & Solounias, 2003), and microwear, the quantification of microscopic marks on the chewing surfaces of the teeth at either low or high magnification (Grine & Kay, 1988; Merceron, Blondel, Bonis, Koufos, & Viriot, 2005; Semprebon et al, 2004; Solounias & Semprebon, 2002; Ungar et al, 2003). DMTA is shown to be an effective method for differentiating a wide array of mammalian taxa based on dietary preference including artiodactyls (Scott, 2012; Ungar, Merceron, et al, 2007; Ungar, Scott, et al, 2007; Ungar et al, 2012), shrews (Withnell & Ungar, 2014), primates (Scott, Teaford, & Ungar, 2012), carnivorans (Desantis, Schubert, Scott, & Ungar, 2012; Schubert, Ungar, & DeSantis, 2010; Ungar, Scott, Schubert, & Stynder, 2010), marsupials (Prideaux et al, 2009), and xenarthrans (Haupt et al, 2013)

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