Evolution of morphological integration. I. Functional units channel stress-induced variation in shrew mandibles

Alexander V. Badyaev, Kerry R. Foresman

Research output: Contribution to journalArticlepeer-review

70 Scopus citations


Stress-induced deviations from normal development are often assumed to be random, yet their accumulation and expression can be influenced by patterns of morphological integration within an organism. We studied within-individual developmental variation (fluctuating asymmetry) in the mandible of four shrew species raised under normal and extreme environments. Patterns of among-individual variation and fluctuating asymmetry were strongly concordant in traits that were involved in the attachment of the same muscles (i.e., functionally integrated traits), and fluctuating asymmetry was closely integrated among these traits, implying direct developmental interactions among traits involved in the same function. Stress-induced variation was largely confined to the directions delimited by functionally integrated groups of traits in the pattern that was concordant with species divergence - species differed most in the same traits that were most sensitive to stress within each species. These results reveal a strong effect of functional complexes on directing and incorporating stress-induced variation during development and might explain the historical persistence of sets of traits involved in the same function in shrew jaws despite their high sensitivity to environmental variation.

Original languageEnglish (US)
Pages (from-to)868-879
Number of pages12
JournalAmerican Naturalist
Issue number6
StatePublished - Jun 2004


  • Developmental plasticity
  • Modularity
  • Morphological integration
  • Sorex shrews
  • Stress
  • Variation

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics


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