Intrasexual selection

Definition

Intrasexual selection is a form of sexual selection where members of the same sex compete for access to mates. This competition can involve physical contests, displays of strength, or other strategies to assert dominance and attract the opposite sex. The outcomes of these interactions can lead to the evolution of traits that enhance competitive abilities, ultimately influencing reproductive success and shaping the evolutionary trajectory of a species.

5 Must Know Facts For Your Next Test

1. Intrasexual selection often leads to the development of physical traits that enhance an individual's competitive ability, such as larger body size or stronger weaponry in males.
2. This form of selection can create a dynamic where successful competitors have more mating opportunities, leading to greater genetic contribution to future generations.
3. Examples of intrasexual selection can be seen in species like deer, where males fight for dominance during mating season.
4. The intensity of intrasexual selection can vary based on factors like population density and sex ratio, impacting how aggressive competition becomes.
5. Intrasexual selection plays a significant role in sexual conflict and can influence the evolution of secondary sexual characteristics.

Review Questions

• How does intrasexual selection influence the physical traits observed in male animals?
  • Intrasexual selection drives the evolution of physical traits that enhance males' competitive abilities. For instance, in many species, males may develop larger body sizes or impressive antlers to outcompete rivals for mates. These traits serve as indicators of strength and fitness, which not only help males win competitions but also signal their quality to potential mates, influencing their reproductive success.
• Discuss the relationship between intrasexual selection and sexual dimorphism within a species.
  • Intrasexual selection often leads to pronounced sexual dimorphism, where males and females exhibit significant differences in size, coloration, or other traits. This occurs because intense competition among males can favor the evolution of specific characteristics that enhance their chances of winning fights or attracting females. As a result, males may become more ornate or larger than females, reflecting their role in mate competition and the selective pressures they face.
• Evaluate how environmental factors might affect the dynamics of intrasexual selection and its outcomes in a given species.
  • Environmental factors such as resource availability, habitat density, and population structure can significantly influence intrasexual selection dynamics. For example, in habitats with limited resources, competition among males may intensify, leading to stronger selection for traits associated with dominance. Conversely, if resources are abundant, the competition may be less aggressive, allowing for more diverse mating strategies to emerge. This variability impacts not only individual success but also shapes evolutionary trajectories within populations over time.

Related terms

Intersexual selection: A type of sexual selection where individuals of one sex choose mates based on specific traits, often leading to the development of elaborate characteristics in the chosen sex.

Sexual dimorphism: The differences in appearance or behavior between males and females of a species, often a result of selective pressures from both intrasexual and intersexual selection.

Mate guarding: A behavior exhibited by one partner in a mating pair to prevent the other from engaging with potential rivals, often seen as a strategy to ensure reproductive success.