Correlates of sexual dimorphism in primates: Ecological and size variables

  • Walter Leutenegger
  • James Cheverud
Article

Abstract

The effects of a series of ecological and size factors on the degree of sexual dimorphism in body weight and canine size were studied among subsets of 70 primate species. Variation in body-weight dimorphism can be almost entirely attributed to body weight (83% of variance R2 of weight dimorphism). Much smaller amounts of the variation can be attributed to mating system (R2 =6.8%,polygynous species being more dimorphic than monogamous ones) and diet (R2 = 2.5%,frugivorous species being more dimorphic than folivorous ones). Habitat (arboreal vs. terrestrial) and activity rhythm (nocturnal vs. diurnal) have only an indirect effect on weight dimorphism. Variation in canine-size dimorphism can be explained in terms of canine size (R2 =49%),activity rhythm (R2 = 20%,diurnal species being more dimorphic than nocturnal ones), and mating system (R2 = 10%).Habitat and diet do not play a significant role in canine-size dimorphism. The unexpectedly high contribution of size to sexual dimorphism coupled with the observation of increased sexual dimorphism with increased size leads us to formulate a new selection model for the evolution of sexual dimorphism. We suggest that if there is selection for size increase, whatever its cause, directional selection in both males and females will lead to an increase in sexual dimorphism based on differences in genetic variance between the sexes. Sexual selection, resource division between the sexes, or lopsided reproductive selection need not play a role in such a model.

Key words

primates sexual dimorphism ecological variability body size canine size 

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Copyright information

© Plenum Publishing Corporation 1982

Authors and Affiliations

  • Walter Leutenegger
    • 1
  • James Cheverud
    • 2
  1. 1.Department of AnthropologyUniversity of WisconsinMadison
  2. 2.Department of AnthropologyNorthwestern UniversityEvanston

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