Convergence in a Mechanically Complex Phenotype: Detecting Structural Adaptations for Crushing in Cichlid Fish

Morphological convergence provides strong evidence that evolution is adaptive. However, putatively convergent morphology is often examined in two dimensions with no explicit model of function. In this study, we investigated structural and mechanical similarities of the lower pharyngeal jaw (LPJ) in...

Full description

Saved in:
Bibliographic Details
Published in:Evolution 2008-07, Vol.62 (7), p.1587-1599
Main Authors: Hulsey, C. Darrin, Roberts, Richard J., Lin, Angela S. P., Guldberg, Robert, Streelman, J. Todd
Format: Article
Language:English
Subjects:
Adaptation, Biological
Animal morphology
Animals
Biological Evolution
Cichlidae
Cichlids - anatomy & histology
Cichlids - genetics
Compressive Strength
Convergent evolution
Crushing
Cuatro Ciénegas
Diet
Evolution
feeding
Finite Element Analysis
Fish
Freshwater
functional morphology
Introns
Jaw
Jaw - anatomy & histology
Jaw - diagnostic imaging
Mollusca
molluscivory
Mollusks
Original s
Phenotype
Phenotypes
speciation
Teeth
Tomography, X-Ray Computed
trophic polymorphism
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Morphological convergence provides strong evidence that evolution is adaptive. However, putatively convergent morphology is often examined in two dimensions with no explicit model of function. In this study, we investigated structural and mechanical similarities of the lower pharyngeal jaw (LPJ) in cichlid fish that have evolved the ability to crush hard-shelled molluscs. Using a novel phylogeny, we demonstrated molluscivory has been gained and/or been lost numerous times in Heroine cichlids. Within this comparative framework, we produced three-dimensional computed tomography (CT) scans for LPJs of both morphotypes in the trophically polymorphic Herichthys minckleyi and six evolutionarily independent pairs of closely related species. Like H. minckleyi, these species exhibit divergence between a molluscivore and a nonmolluscivore. Using the CT scans, we generated finite element models of papilliform H. minckleyi LPJs to determine where stress would concentrate in a jaw not modified to crush molluscs. Then, we examined whether stress in the papilliform LPJ predicted structural modifications in molariform H. minckleyi and other molluscivorous species. Despite potential constraints, stresses imposed during prey processing explain 40% of LPJ variation in mollusc crushing species. The structural and mechanical analyses also suggest divergence found in polymorphic species could provide the substrate for trophic differences found in reproductively isolated cichlids.
ISSN:0014-3820
1558-5646
DOI:10.1111/j.1558-5646.2008.00384.x