title: The relationship between cranial structure, biomechanical performance and ecological diversity in varanoid lizards.
abstract: Skull structure is intimately associated with feeding ability in vertebrates, both in terms of specific performance measures and general ecological characteristics. This study quantitatively assessed variation in the shape of the cranium and mandible in varanoid lizards, and its relationship to structural performance (von Mises strain) and interspecific differences in feeding ecology. Geometric morphometric and linear morphometric analyses were used to evaluate morphological differences, and finite element analysis was used to quantify variation in structural performance (strain during simulated biting, shaking and pulling). This data was then integrated with ecological classes compiled from relevant scientific literature on each species in order to establish structure-function relationships. Finite element modelling results showed that variation in cranial morphology resulted in large differences in the magnitudes and locations of strain in biting, shaking and pulling load cases. Gracile species such as Varanus salvadorii displayed high strain levels during shaking, especially in the areas between the orbits. All models exhibit less strain during pull back loading compared to shake loading, even though a larger force was applied (pull =30N, shake = 20N). Relationships were identified between the morphology, performance, and ecology. Species that did not feed on hard prey clustered in the gracile region of cranial morphospace and exhibited significantly higher levels of strain during biting (P = 0.0106). Species that fed on large prey clustered in the elongate area of mandible morphospace. This relationship differs from those that have been identified in other taxonomic groups such as crocodiles and mammals. This difference may be due to a combination of the open 'space-frame' structure of the varanoid lizard skull, and the 'pull back' behaviour that some species use for processing large prey.
authors.affiliation: Department of Anatomy and Developmental Biology, Monash University, Melbourne, Australia; School of Environmental and Life Science, University of Newcastle, Newcastle, Australia; Geosciences, Museum Victoria, Melbourne, Australia.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: McCurry
authors.affiliation: School of Environmental and Life Science, University of Newcastle, Newcastle, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Mahony
authors.affiliation: School of Engineering, University of Newcastle, Newcastle, Australia.
authors.forename: Phillip D
authors.initials: PD
authors.lastname: Clausen
authors.affiliation: Department of Anatomy and Developmental Biology, Monash University, Melbourne, Australia.
authors.forename: Michelle R
authors.initials: MR
authors.lastname: Quayle
authors.affiliation: Department of Anatomy and Developmental Biology, Monash University, Melbourne, Australia.
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Walmsley
authors.affiliation: Department of Zoology, University of Melbourne, Melbourne, Australia.
authors.forename: Tim S
authors.initials: TS
authors.lastname: Jessop
authors.affiliation: School of Engineering, University of Newcastle, Newcastle, Australia; The Function, Evolution & Anatomy Research Lab, Zoology Division, School of Environmental and Rural Sciences, University of New England, Armidale, Australia.
authors.forename: Stephen
authors.initials: S
authors.lastname: Wroe
authors.affiliation: School of Engineering, University of Newcastle, Newcastle, Australia.
authors.forename: Heather
authors.initials: H
authors.lastname: Richards
authors.affiliation: Department of Anatomy and Developmental Biology, Monash University, Melbourne, Australia; School of Engineering, University of Newcastle, Newcastle, Australia.
authors.forename: Colin R
authors.initials: CR
authors.lastname: McHenry
mesh_terms: D000818:Animals; D044822:Biodiversity; D001696:Biomechanical Phenomena; D001732:Bite Force; D020342:Finite Element Analysis; D016014:Linear Models; D008116:Lizards / Q000033:anatomy & histology* / Q000502:physiology; D008334:Mandible / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology; D010802:Phylogeny; D011235:Predatory Behavior; D012886:Skull / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology; D013045:Species Specificity; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed