Self-recognition, color signals, and cycles of greenbeard mutualism and altruism

Barry Sinervo, Alexis Chaine, Jean Clobert, Ryan Calsbeek, Lisa Hazard, Lesley Lancaster, Andrew G. McAdam, Suzanne Alonzo, Gwynne Corrigan, Michael E. Hochberg

Research output: Contribution to journalArticlepeer-review

132 Scopus citations


Altruism presents a challenge to evolutionary theory because selection should favor selfish over caring strategies. Green beard altruism resolves this paradox by allowing cooperators to identify individuals carrying similar alleles producing a form of genic selection. In side-blotched lizards, genetically similar but unrelated blue male morphs settle on adjacent territories and cooperate. Here we show that payoffs of cooperation depend on asymmetric costs of orange neighbors. One blue male experiences low fitness and buffers his unrelated partner from aggressive orange males despite the potential benefits of defection. We show that recognition behavior is highly heritable in nature, and we map genetic factors underlying color and self-recognition behavior of genetic similarity in both sexes. Recognition and cooperation arise from genome-wide factors based on our mapping study of the location of genes responsible for self-recognition behavior, recognition of blue color, and the color locus. Our results provide an example of greenbeard interactions in a vertebrate that are typified by cycles of greenbeard mutualism interspersed with phases of transient true altruism. Such cycles provide a mechanism encouraging the origin and stability of true altruism.

Original languageEnglish
Pages (from-to)7372-7377
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number19
StatePublished - 9 May 2006


  • Alternative strategies
  • Cooperation
  • Evolutionarily stable strategy
  • Frequency-dependent selection
  • Linkage map


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