Incisor morphology reflects diet in caviomorph rodents

Abstract

Rodents are important components of most modern ecosystems. Understanding their roles in paleocommunities requires robust methods for inferring diet and other autecological characteristics. This pilot study tests whether a relationship between incisor morphology and diet exists among extant rodents that might be used to infer diets of extinct species. We focused on 11 genera of caviomorph rodents classified in 3 dietary categories: fruit-leaf, fruit-seed, and grass-leaf. For each genus 6 variables describing morphology of the upper incisor were measured on 5 specimens. Data were analyzed using a series of stepwise discriminant analyses. Discriminant analyses correctly predicted diets of nearly all training cases (,95%) using 4 incisor characteristics. Five additional species (1 caviomorph and 4 noncaviomorph), treated as unknowns, also were classified correctly. Jackknife analyses correctly predicted diets of approximately two-thirds of training cases. Our study indicates that incisor morphology is related to diet in extant caviomorph rodents. Incisor data therefore might be useful for inferring diets of extinct species.Key words: dentition, discriminant analysis, ecomorphology, herbivory, hystricognath, paleoecology, South America All modern rodents possess a pair of hypselodont, chisellike incisors in the upper and lower jaws (Landry 1999;Meng and Wyss 2005;Van Valen 2004). These enlarged teeth arguably are the most easily recognized characteristic of rodents, and it is for these gnawing teeth that rodents are named (from the Latin rodere, meaning to gnaw). In addition to their obvious role in food acquisition and processing, these gnawing incisors are used by some species for digging, defense, or cutting tough materials such as wood (Nowak 1999). Relative to their morphological prominence and functional importance in rodents, rodent incisors have been the focus of surprisingly little ecomorphological investigation. Most recent studies that have examined rodent incisors in an ecological context have attempted to correlate their morphology with digging behavior rather than diet (e.g., Fernández et al. 2000;Hopkins and Davis 2009;Millien and Jaeger 2001;Millien-Parra 2000;Mora et al. 2003;Rybczynski 1999). Other studies have focused on size evolution and guild partitioning among a small number of sympatric species using incisor data and have demonstrated character displacement indicative of dietary resource partitioning (Ben-Moshe et al. 2001; Dayan and Simberloff 1994;Parra et al. 1999). Although a recent study by Samuels (2009) explored how cranial morphology differs among major dietary categories of rodents (e.g., carnivores, generalist herbivores, and omnivores), no study yet has focused solely on the relationship between incisor morphology and diet in rodents nor attempted to discriminate among herbivore diets at a finer scale.The aim of our pilot study is to test whether a relationship between incisor morphology and diet exists among primarily herbivorous rodents. We do so by focusing on a morphologicall...

First Approach to the Paleobiology of Extinct Prospaniomys (Rodentia, Hystricognathi, Octodontoidea) Through Head Muscle Reconstruction and the Study of Craniomandibular Shape Variation

“…Most living rodents are herbivorous or omnivorous while some species are carnivores, piscivores, and insectivores (Samuels 2009). Caviomorphs can be regarded as mainly herbivorous (Croft et al 2011), while some echimyids species are omnivorous or at least incorporate some animal material (Nowak 1991); insectivory has been proposed for some extant echimyids and fossil octodontoids (Vucetich and Verzi 1996;Lessa and Costa 2009). Broadly, herbivores can be split into generalized and specialist categories (Samuels 2009).…”

“…In addition, the ingestion of intrinsic and exogenous abrasives by graminivorous species is related to an increase in tooth wear and the degree of hypsodonty (Williams and Kay 2001). Among caviomorphs, taxa that are known to feed on grass have hypsodont molars (see Williams and Kay 2001), whereas the diet of living taxa that present low-crowned teeth, as is the case of living echimyids, includes leaves and fruits and may incorporate insects (Nowak 1991;Croft et al 2011). Hence, the overall moderate development of the masticatory musculature displayed by Prospaniomys could suggest an omnivorous or generalized herbivorous diet.…”

“…Additionally, an anteriorly extended masseter medialis pars infraorbitalis can be related to nuts and seeds gnawing, or to folivory (Cox et al , 2013Herrel et al 2012). Moreover, the molar morphology, the moderate tooth row length, and the presence of orthodont, short, and uncompressed incisors (Arnal and Kramarz 2011) are features that can be linked to this kind of diet (Croft et al 2011).…”

The partitioning of food resources between two rodents in the subtropical region of southern Brazil

“…Most likely, the dietary selectivity of both rodents (Escobar and González-Jiménez 1976, Quintana et al 1998, Quintana 2002, Guichón et al 2003a, Borges and Colares 2007, Galende et al 2013, the relative palatability of the plants available for foraging, and the strong relationship between energy content and fiber (Molano 1994, Colares et al 2010) explain a number of the similarities observed between the diets of the two rodents. Another characteristic to note is the similarity of the morphology of the oral apparatus, e.g., the incisor teeth of both rodents, which can directly shape the similarity between species in the use of food resources (Croft and Niemi 2011).…”

The ecomorphology of southern African rodent incisors: Potential applications to the hominin fossil record

“…Upper incisors of Rhabdomys pumilio with the measurements adapted from Croft et al [28] marked. Abbreviations: BD, buccolingual diameter; DE, distal enamel extent; MD, mesiodistal diameter; OD, buccolingual occlusal diameter; RC, outer radius of curvature; OA, occlusal angle.…”