title: Mechanical sensitivity and the dynamics of evolutionary rate shifts in biomechanical systems.
abstract: The influence of biophysical relationships on rates of morphological evolution is a cornerstone of evolutionary theory. Mechanical sensitivity-the correlation strength between mechanical output and the system's underlying morphological components-is thought to impact the evolutionary dynamics of form-function relationships, yet has rarely been examined. Here, we compare the evolutionary rates of the mechanical components of the four-bar linkage system in the raptorial appendage of mantis shrimp (Order Stomatopoda). This system's mechanical output (kinematic transmission (KT)) is highly sensitive to variation in its output link, and less sensitive to its input and coupler links. We found that differential mechanical sensitivity is associated with variation in evolutionary rate: KT and the output link exhibit faster rates of evolution than the input and coupler links to which KT is less sensitive. Furthermore, for KT and, to a lesser extent, the output link, rates of evolution were faster in 'spearing' stomatopods than 'smashers', indicating that mechanical sensitivity may influence trait-dependent diversification. Our results suggest that mechanical sensitivity can impact morphological evolution and guide the process of phenotypic diversification. The connection between mechanical sensitivity and evolutionary rates provides a window into the interaction between physical rules and the evolutionary dynamics of morphological diversification.
authors.affiliation: Department of Biology, Duke University, Durham, NC 27708, USA mmm109@duke.edu.
authors.forename: Martha M
authors.identifier: 0000-0001-8297-2396
authors.initials: MM
authors.lastname: Muñoz
authors.affiliation: Department of Animal Biology, University of Illinois, Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Philip S L
authors.identifier: 0000-0001-7133-8322
authors.initials: PS
authors.lastname: Anderson
authors.affiliation: Department of Biology, Duke University, Durham, NC 27708, USA.
authors.forename: S N
authors.initials: SN
authors.lastname: Patek
mesh_terms: D000825:Animal Structures / Q000033:anatomy & histology*; D000818:Animals; D005075:Biological Evolution; D001696:Biomechanical Phenomena; D003445:Crustacea / Q000033:anatomy & histology*
keywords: biomechanics; comparative phylogenetics; evolution; mantis shrimp; many-to-one mapping; scaling