Testing adaptive hypotheses of convergence with functional landscapes: a case study of bone-cracking hypercarnivores

PLoS One. 2013 May 29;8(5):e65305. doi: 10.1371/journal.pone.0065305. Print 2013.

Abstract

Morphological convergence is a well documented phenomenon in mammals, and adaptive explanations are commonly employed to infer similar functions for convergent characteristics. I present a study that adopts aspects of theoretical morphology and engineering optimization to test hypotheses about adaptive convergent evolution. Bone-cracking ecomorphologies in Carnivora were used as a case study. Previous research has shown that skull deepening and widening are major evolutionary patterns in convergent bone-cracking canids and hyaenids. A simple two-dimensional design space, with skull width-to-length and depth-to-length ratios as variables, was used to examine optimized shapes for two functional properties: mechanical advantage (MA) and strain energy (SE). Functionality of theoretical skull shapes was studied using finite element analysis (FEA) and visualized as functional landscapes. The distribution of actual skull shapes in the landscape showed a convergent trend of plesiomorphically low-MA and moderate-SE skulls evolving towards higher-MA and moderate-SE skulls; this is corroborated by FEA of 13 actual specimens. Nevertheless, regions exist in the landscape where high-MA and lower-SE shapes are not represented by existing species; their vacancy is observed even at higher taxonomic levels. Results highlight the interaction of biomechanical and non-biomechanical factors in constraining general skull dimensions to localized functional optima through evolution.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Physiological / physiology*
  • Animals
  • Biological Evolution*
  • Biomechanical Phenomena
  • Carnivora / anatomy & histology*
  • Carnivora / classification
  • Carnivora / physiology*
  • Finite Element Analysis
  • Fossils
  • Models, Anatomic
  • Population Dynamics
  • Skull / anatomy & histology*

Grant support

This research was supported by a National Science Foundation Graduate Research Fellowship and a Doctoral Dissertation Improvement Grant (DEB-0909807), American Society of Mammalogists Grant in Aid of Research, United States Fulbright Program, and a University of Southern California Zumberge Grant. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.