Evolutionary patterns of shape and functional diversification in the skull and jaw musculature of triggerfishes (Teleostei: Balistidae)

Abstract

The robust skull and highly subdivided adductor mandibulae muscles of triggerfishes provide an excellent system within which to analyze the evolutionary processes underlying phenotypic diversification. We surveyed the anatomical diversity of balistid jaws using Procrustes-based geometric morphometric analyses and a phylomorphospace approach to quantifying morphological transformation through evolution. We hypothesized that metrics of interspecific cranial shape would reveal patterns of phylogenetic diversification that are congruent with functional and ecological transformation. Morphological landmarks outlining skull and adductor mandibulae muscle shape were collected from 27 triggerfish species. Procrustes-transformed skull shape configurations revealed significant phylogenetic and size-influenced structure. Phylomorphospace plots of cranial shape diversity reveal groupings of shape between different species of triggerfish that are mostly consistent with phylogenetic relatedness. Repeated instances of convergence upon similar cranial shape by genetically disparate taxa are likely due to the functional demands of shared specialized dietary habits. This study shows that the diversification of triggerfish skulls occurs via modifications of cranial silhouette and the positioning of subdivided jaw adductor muscles. Using the morphometric data collected here as input to a biomechanical model of triggerfish jaw function, we find that subdivided jaw adductors, in conjunction with a unique cranial skeleton, have direct biomechanical consequences that are not always congruent with phylomorphospace patterns in the triggerfish lineage. The integration of geometric morphometrics with biomechanical modeling in a phylogenetic context provides novel insight into the evolutionary patterns and ecological role of muscle subdivisions in triggerfishes. J. Morphol. 277:737-752, 2016. © 2016 Wiley Periodicals, Inc.

DNA barcoding uncovers extensive cryptic diversity in the African long‐fin tetra Bryconalestes longipinnis (Alestidae: Characiformes)

“…Due to the presence of sexual dimorphism in the examined specimens, a 10,000 permutation multivariate analysis of covariance (MANCOVA) with shape grouped by sex and log‐centroid size as the covariate was first used to test whether males and females had similar allometric slopes, such that a single function could be used to adjust for size. Next, regressions of shape on log‐centroid size were performed, taking the residuals as size‐corrected shape data (Martinez & Sparks, ; McCord & Westneat, ). A MANOVA, with significance based on 10,000 permutations, was used to compare whether morphologies of allometrically‐adjusted shape data differed between UG and LG.…”

Study of morphological variation of northern Neotropical Ariidae reveals conservatism despite macrohabitat transitions

“…The other approach (ii) examines species diversification from an adaptational perspective by investigating factors such as predator avoidance, niche occupation, or ecological functioning. In this context, previous studies either focused on the biomechanical link of skull or mandible shape to functional ecology [ 13 – 17 ] or explicitly investigated convergent evolution of skull shape and biotic and abiotic covariates [ 6 , 16 , 18 , 19 ]. Other studies are exploratory or descriptive in nature [ 20 – 22 ].…”

Body size and mortality rates in coral reef fishes: a three-phase relationship

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