title: Diet, bite force and skull morphology in the generalist rodent morphotype.
abstract: For many vertebrate species, bite force plays an important functional role. Ecological characteristics of a species' niche, such as diet, are often associated with bite force. Previous evidence suggests a biomechanical trade-off between rodents specialized for gnawing, which feed mainly on seeds, and those specialized for chewing, which feed mainly on green vegetation. We tested the hypothesis that gnawers are stronger biters than chewers. We estimated bite force and measured skull and mandible shape and size in 63 genera of a major rodent radiation (the myomorph sigmodontines). Analysis of the influence of diet on bite force and morphology was made in a comparative framework. We then used phylogenetic path analysis to uncover the most probable causal relationships linking diet and bite force. Both granivores (gnawers) and herbivores (chewers) have a similar high bite force, leading us to reject the initial hypothesis. Path analysis reveals that bite force is more likely influenced by diet than the reverse causality. The absence of a trade-off between herbivores and granivores may be associated with the generalist nature of the myomorph condition seen in sigmodontine rodents. Both gnawing and chewing sigmodontines exhibit similar, intermediate phenotypes, at least compared to extreme gnawers (squirrels) and chewers (chinchillas). Only insectivorous rodents appear to be moving towards a different direction in the shape space, through some notable changes in morphology. In terms of diet, natural selection alters bite force through changes in size and shape, indicating that organisms adjust their bite force in tandem with changes in food items.
authors.affiliation: Programa de Pós-Graduação em Ecologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil. renanmaestri@gmail.com.
authors.forename: R
authors.identifier: 0000-0001-9134-2943
authors.initials: R
authors.lastname: Maestri
authors.affiliation: Integrative Research Center, Field Museum of Natural History, Chicago, IL, USA.
authors.forename: B D
authors.initials: BD
authors.lastname: Patterson
authors.affiliation: Programa de Pós-Graduação em Ecologia, Universidade Regional Integrada do Alto Uruguai e das Missões, Erechim, RS, Brazil.
authors.forename: R
authors.initials: R
authors.lastname: Fornel
authors.affiliation: Laboratório de Ciências Ambientais, CBB, Universidade Estadual do Norte Fluminense, Campos dos Goytacazes, RJ, Brazil.
authors.forename: L R
authors.initials: LR
authors.lastname: Monteiro
authors.affiliation: Programa de Pós-Graduação em Ecologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.|Departamento de Genética, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: T R O
authors.initials: TR
authors.lastname: de Freitas
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001696:Biomechanical Phenomena; D001732:Bite Force; D004032:Diet; D010802:Phylogeny; D012377:Rodentia / Q000033:anatomy & histology*; D012886:Skull
keywords: Rodentia; chew; diet evolution; feeding; functional morphology; gnaw; myomorph; natural selection; phylogenetic path analysis; sigmodontines