Intrinsic and extrinsic drivers of shape variation in the Albatross compound bill

Josh Tyler, David P. Hocking, Jane L. Younger

Research output: Contribution to journalArticlepeer-review

Abstract

Albatross are the largest seabirds on Earth and have a suite of adaptations for their pelagic lifestyle. Rather than having a bill made of a single piece of keratin, Procellariiformes have a compound rhamphotheca, made of several joined plates. Drivers of the shape of the albatross bill have not been explored. Here we use three-dimensional scans of 61 upper bills from 12 species of albatross to understand whether intrinsic (species assignment & size) or extrinsic (diet) factors predict bill shape. Diet is a significant predictor of bill shape with coarse dietary categories providing higher R2 values than dietary proportion data. We also find that of the intrinsic factors, species assignment accounts for ten times more of the variation than size (72% versus 6.8%) and that there is a common allometric vector of shape change between all species. When considering species averages in a phylogenetic framework, there are significant Blomberg's K results for both shape and size (K = 0.29 & 1.10) with the first axis of variation having a much higher K value (K = 1.9), reflecting the split in shape at the root of the tree. The influence of size on bill shape is limited, with species assignment and diet predicting far more of the variation. The results show that both intrinsic and extrinsic factors are needed to understand morphological evolution.

Original languageEnglish
Article number230751
JournalRoyal Society Open Science
Volume10
Issue number8
Early online date16 Aug 2023
DOIs
Publication statusPublished - 16 Aug 2023

Bibliographical note

Funding Information:
J.T. is supported by the Evolution Education Trust and University of Bath. Acknowledgements

Keywords

  • albatross
  • allometry
  • bill
  • diet
  • morphospace

ASJC Scopus subject areas

  • General

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