The Dimensionality of the Mating Environment Predicts Male Combat and Sexual Coercion in Turtles

Open Access
Mckinnon, Leela
Area of Honors:
Bachelor of Arts
Document Type:
Thesis Supervisors:
  • David Andrew Puts, Thesis Supervisor
  • Timothy Michael Ryan, Honors Advisor
  • Contest competition
  • dimensionality hypothesis
  • sexual selection
  • sexual coercion
  • Testudines
Predicting which mechanisms of sexual selection will be in effect in a given species is a topic of ongoing research. It has previously been suggested that terrestrial species have a higher degree of male combat than aquatic species. The hypothesis tested in this thesis is that the dimensionality of the mating environment will influence the evolution of both male combat and sexual coercion. Specifically, male combat and sexual coercion should be more likely to evolve in two-dimensional mating environments, in which females are easier to monopolize and constrain, than in three-dimensional environments where males are easier to evade by both same-sex competitors and females. In a large sample of turtle species with a diversity of mating dimensionalities, we tested the hypothesis that dimensionality predicts the degree of male combat and sexual coercion that will occur in a given species. As predicted, we found that male combat, sexual coercion, large male size, and male weapons are more likely to occur in species in which males compete for mates two-dimensionally than in species in which males compete for mates three-dimensionally. These data support the dimensionality hypothesis and contribute to a greater understanding of the forms that sexual selection will take in a given species.