Evolutionary Biology

, Volume 37, Issue 4, pp 200–209 | Cite as

Sexual Selection, Ontogenetic Acceleration, and Hypermorphosis Generates Male Trimorphism in Wellington Tree Weta

  • Clint D. KellyEmail author
  • Dean C. Adams
Research Article


Strong sex-specific selection on traits common to both sexes typically results in sexual dimorphism. Here we find that Wellington tree weta (Hemideina crassidens) are sexually dimorphic in both head shape and size due to differential selection pressures on the sexes: males use their heads in male-male combat and feeding whereas females use theirs for feeding only. Remarkably, the sexes share a common ontogenetic trajectory with respect to head growth. Male head shape allometry is an extension of the female’s trajectory despite maturing two instars earlier, a feat achieved through ontogenetic acceleration and hypermorphosis. Strong sexual selection also favours the evolution of alternative reproductive strategies in which some males produce morphologically different weapons. Wild-caught male H. crassidens are trimorphic with regard to weapon size, a rare phenomenon in nature, and weapon shape is related to each morph’s putative mating strategy.


Morphometrics Sexual selection Weaponry Shape Allometry Sexually dimorphism 



We thank Wolf Blanckenhorn and two anonymous referees for valuable comments on the manuscript. This work was supported in part by faculty start-up funds awarded to CDK by Iowa State University and NSF grant DEB-0446758 to DCA.


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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  1. 1.Department of Ecology, Evolution & Organismal BiologyIowa State UniversityAmesUSA

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