Year: 2011
Type: article
Abstract: Descriptive and quantitative analyses of electromyograms (EMG) from the jaw adductors during feeding in mammals have demonstrated both similarities and differences among species in chewing motor patterns. These observations have led to a number of hypotheses of the evolution of motor patterns, the most comprehensive of which was proposed by Weijs in 1994. Since then, new data have been collected and additional hypotheses for the evolution of motor patterns have been proposed. Here, we take advantage of these new data and a well-resolved species-level phylogeny for mammals to test for the correlated evolution of specific components of mammalian chewing motor patterns. We focus on the evolution of the coordination of working-side (WS) and balancing-side (BS) jaw adductors (i.e., Weijs' Triplets I and II), the evolution of WS and BS muscle recruitment levels, and the evolution of asynchrony between pairs of muscles. We converted existing chewing EMG data into binary traits to incorporate as much data as possible and facilitate robust phylogenetic analyses. We then tested hypotheses of correlated evolution of these traits across our phylogeny using a maximum likelihood method and the Bayesian Markov Chain Monte Carlo method. Both sets of analyses yielded similar results highlighting the evolutionary changes that have occurred across mammals in chewing motor patterns. We find support for the correlated evolution of (1) Triplets I and II, (2) BS deep masseter asynchrony and Triplets I and II, (3) a relative delay in the activity of the BS deep masseter and a decrease in the ratio of WS to BS muscle recruitment levels, and (4) a relative delay in the activity of the BS deep masseter and a delay in the activity of the BS posterior temporalis. In contrast, changes in relative WS and BS activity levels across mammals are not correlated with Triplets I and II. Results from this work can be integrated with dietary and morphological data to better understand how feeding and the masticatory apparatus have evolved across mammals in the context of new masticatory demands.
DOI: 10.1093/icb/icr068
Language: English
Subfield: Paleontology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: bronze
Awards: Craniofacial Biomechanics of Primates, MUSCULAR EFFECT ON MANDIBULAR MOVEMENTS, The mechanics of anterior tooth use in primates, Craniofacial Biomechanics in Camelids: In vivo and Comparative Studies in Form and Function, Symposium: Synthesis of Physiologic Data from the Mammalian Feeding Apparatus using FEED, the Feeding Experiments End-User Database, Salt Lake City, Utah, G1844757719, STRESS ANALYSIS OF THE POST ORIBITAL BAR IN PRIMATES, G1861594329, G3300230432, DOCTORAL DISSERTATION RESEARCH: Symphyseal Fusion in Ungulates and Anthropoids: A Case of Functional Convergence?, Jaw-Muscle Biomechanics in Primates, Dissertation Research: The Functional Significance of the Anthropoid Postorbital Septum, Adductor Muscle Function and Fiber Type in Macaca and Papio
OpenAlex ID: W2100360567