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Testing the cranial evolutionary allometric 'rule' in Galliformes.

M Linde-Medina1

  • 1Faculty of Life Sciences, University of Manchester, Manchester, UK. linde.m@outlook.com.

Journal of Evolutionary Biology
|June 17, 2016
PubMed
Summary
This summary is machine-generated.

The common cranial evolutionary allometric (CREA) pattern may be overestimated. While Galliformes show CREA in overall shape, beak size relative to braincase size indicates negative allometry, not the expected positive allometry.

Keywords:
allometrybrain sizeconstraintgeometric morphometrics

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Area of Science:

  • Evolutionary biology
  • Comparative anatomy
  • Paleontology

Background:

  • Recent studies suggest a common cranial evolutionary allometric (CREA) pattern in mammals and birds.
  • This pattern describes smaller species having relatively smaller faces and larger braincases than larger species.
  • Cranial allometry is typically assessed via multivariate regression of shape against size, accounting for phylogeny.

Purpose of the Study:

  • To investigate cranial allometry in 83 Galliformes species using two distinct analytical approaches.
  • To determine if the common cranial evolutionary allometric (CREA) pattern is present in Galliformes.
  • To explore the relationship between beak size and braincase size allometry in this avian group.

Main Methods:

  • Applied multivariate regression of cranial shape (landmark coordinates) against centroid size, controlling for phylogenetic relatedness.
  • Utilized bivariate regression to analyze the allometric relationship between beak size and braincase size.
  • Examined a dataset of 83 Galliformes species with body weights ranging from 30g to 2.5kg.

Main Results:

  • Multivariate analysis revealed a significant allometric pattern consistent with the CREA pattern in Galliformes.
  • Bivariate regression indicated negative allometry between beak size and braincase size.
  • Contrary to CREA expectations, larger Galliformes species exhibited disproportionally shorter beaks relative to their braincases.

Conclusions:

  • The CREA pattern may be overestimated when using overall cranium size as the sole metric.
  • Galliformes exhibit a mixed pattern of allometry, with overall shape supporting CREA but beak-braincase proportions contradicting it.
  • Further research is needed to refine the understanding of cranial allometry and its evolutionary drivers across diverse taxa.