Intrasexual selection predicts the evolution of signal complexity in lizards

T. J. Ord*, D. T. Blumstein, C. S. Evans

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

87 Citations (Scopus)


Sexual selection has often been invoked in explaining extravagant morphological and behavioural adaptations that function to increase mating success. Much is known about the effects of intersexual selection, which operates through female mate choice, in shaping animal signals. The role of intrasexual selection has been less clear. We report on the first evidence for the coevolution of signal complexity and sexual size dimorphism (SSD), which is characteristically produced by high levels of male-male competition. We used two complementary comparative methods in order to reveal that the use of complex signals is associated with SSD in extant species and that historical increases in complexity have occurred in regions of a phylogenetic tree characterized by high levels of pre-existing size dimorphism. We suggest that signal complexity has evolved in order to improve opponent assessment under conditions of high male-male competition. Our findings suggest that intrasexual selection may play an important and previously underestimated role in the evolution of communicative systems.

Original languageEnglish
Pages (from-to)737-744
Number of pages8
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1468
Publication statusPublished - 7 Apr 2001


  • Evolution
  • Sexual selection
  • Sexual size dimorphism
  • Signal complexity
  • The comparative method
  • Visual communication


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