Environmental variation shapes sexual dimorphism in red deer

Area of Science:

• Evolutionary biology
• Ecology
• Animal behavior

Background:

• Sexual dimorphism in mammals arises from differing reproductive strategies: male competition for mates and female competition for resources.
• In polygynous species, males typically exhibit rapid growth for size, while females prioritize early maturity and condition over size.
• Environmental factors can influence these divergent growth strategies, potentially altering sexual size dimorphism.

Purpose of the Study:

• To investigate how environmental changes, specifically climate warming and altered plant phenology, affect sexual size dimorphism in red deer.
• To test the hypothesis that environmental factors differentially influence male and female growth and reproductive strategies.

Main Methods:

• Analysis of red deer growth and reproductive data over 32 years of winter warming and 15 years of earlier plant phenology.
• Comparison of male and female growth trajectories and reproductive investment in response to climatic and phenological shifts.

Main Results:

• Warmer climate led to increased male growth rates and adult size, while female size decreased.
• Earlier plant phenology promoted increased female condition and earlier reproduction, but not male reproductive timing or size.
• Adult size dimorphism increased with warming temperatures and decreased with improved forage quality.

Conclusions:

• Environmental variation, particularly climate change, significantly molds the evolutionary trajectories of male and female growth strategies.
• Divergent responses to environmental factors can exacerbate or mitigate existing sexual size dimorphism.
• Understanding these dynamics is crucial for predicting species' adaptation to changing environments.