Antler size in red deer: heritability and selection but no evolution

Area of Science:

• Evolutionary Biology
• Animal Behavior
• Quantitative Genetics

Background:

• Secondary sexual traits, like red deer antlers, are crucial for sexual selection.
• Understanding the interplay between heritability, selection, and evolutionary response is key in evolutionary studies.

Purpose of the Study:

• To estimate the heritability and selection on antler size in a wild red deer population.
• To investigate whether observed selection on antler size translates into an evolutionary response.

Main Methods:

• Quantified antler size and lifetime breeding success in a wild red deer population over nearly 30 years.
• Estimated heritability of antler size using quantitative genetic methods.
• Calculated selection gradients to assess the strength and direction of selection.

Main Results:

• Male red deer with larger antlers exhibited significantly higher lifetime breeding success (selection gradient = 0.44).
• Antler size was found to be heritable (heritability = 0.33), indicating a genetic component.
• Despite directional selection and heritability, no evolutionary increase in antler size was observed over the study period.

Conclusions:

• The lack of evolutionary response suggests that environmental covariances, such as nutritional state, may mask the effects of genetic variation and selection on antler size.
• Environmental factors influencing both antler development and mating success can decouple phenotypic selection from genetic change.
• This study highlights the complexity of evolutionary processes, where environmental influences can override direct selection on heritable traits.