Evolutionary Biology

, Volume 43, Issue 1, pp 12–25

The Craniolingual Morphology of Waterfowl (Aves, Anseriformes) and Its Relationship with Feeding Mode Revealed Through Contrast-Enhanced X-Ray Computed Tomography and 2D Morphometrics

Research Article

DOI: 10.1007/s11692-015-9345-4

Cite this article as:
Li, Z. & Clarke, J.A. Evol Biol (2016) 43: 12. doi:10.1007/s11692-015-9345-4

Abstract

Within Anseriformes, waterfowl (ducks, geese, and swans) exhibit three specialized feeding modes that are distinctive among Aves: filter-feeding with fine and dense keratinous lamellae on a flat, mediolaterally expanded bill; cropping or grazing vegetation with large and robust lamellae with a dorsoventrally expanded bill; and sharp lamellae associated with a narrow bill used in acquiring mixed invertebrates and fish underwater mainly by grasping. Here we assess morphometric variation in cranial and hyolingual structures as well as hyolingual myology in a diverse sample of Anatidae to explore the relationship of tongue variation and feeding mode. Phylogenetically informed principal component analysis (phyl.PCA) of cranial-lingual measurements for 67 extant and two extinct anatids recovers grazers and filter-feeding taxa in largely distinct areas of morphospace, while underwater graspers and other mixed feeders show less distinct clustering. The relationship between morphometric differences in skeletal features and muscular variation was further explored through a reassessment of hyolingual musculature enabled by contrast-enhanced X-ray computed tomography (CT) imagery acquired from three exemplar species (Branta canadensis, Chen caerulescens, and Aythya americana) with distinctive ecologies and morphologies of the bony hyoid. Data for these duck and geese exemplars reveal further significant, and previously unstudied, morphological differences between filter-feeding and grazing species. Grazers have a larger hyolingual apparatus with highly-developed extrinsic hyoid muscles; while filter-feeding species are characterized by relatively more diminutive extrinsic hyoid muscles and larger intrinsic hyoid muscles. The feeding modes of two extinct taxa (i.e., Presbyornis and Thambetochen) were also estimated from morphometric data. The results indicate a derived terrestrial browsing or grazing ecology for Thambetochen but do not unequivocally support a specialized filter-feeding ecology for Presbyornis, which is recovered with mixed feeders including swans. The combination of detailed, CT-mediated acquisition of fine muscular anatomy with morphometric approaches shows promise for illuminating form–function relationships in extant taxa more generally.

Keywords

AnatidaeFeeding modesHyoidMorphometrics

Supplementary material

11692_2015_9345_MOESM1_ESM.xlsx (22 kb)
Appendix 1Skeletal measurements of the hyoid apparatus and skull, feeding types and body mass data used in the phylogenetically informed principle component analysis. (XLSX 21 kb)
11692_2015_9345_MOESM2_ESM.docx (13 kb)
Appendix 2Phylo.tree files used in the three analyses. Selected phylogeny from “Birdtree.org” (Jetz et al. 2012), Livezey (1997a, b) and Sorenson et al. (1999). (DOCX 13 kb)
11692_2015_9345_MOESM3_ESM.csv (5 kb)
Appendix 3Loadings and variance explained by phylogenetic principal component analyses of the phylogenetically size-corrected measurements. (CSV 4 kb)

Copyright information

© Springer Science+Business Media New York 2015

Authors and Affiliations

  1. 1.Department of Geological SciencesUniversity of Texas at AustinAustinUSA