Sexual Selection,Ontogenetic Acceleration,and Hypermorphosis Generates Male Trimorphism in Wellington Tree Weta |
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Authors: | Clint D Kelly Dean C Adams |
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Institution: | (1) Department of Ecology, Evolution & Organismal Biology, Iowa State University, Ames, IA 50011, USA |
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Abstract: | 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. |
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