Sexual selection and temporal phenotypic variation in a damselfly population.

Area of Science:

• Evolutionary Biology
• Behavioral Ecology
• Quantitative Genetics

Background:

• Temporal variation in selection is driven by shifts in fitness landscapes or phenotypic distributions.
• Sexual selection on body size in damselflies provides a model for studying these dynamics.
• Understanding selection requires analyzing both fitness surfaces and phenotype distributions over time.

Purpose of the Study:

• To investigate the causes of temporal variation in sexual selection on body size in Enallagma aspersum.
• To differentiate the roles of fitness surface changes versus phenotypic distribution changes in driving selection.
• To provide a comprehensive framework for inferring selection dynamics.

Main Methods:

• Within- and between-generation sampling of fitness surfaces and phenotypic distributions over two years.
• Analysis of body size distributions in male and female damselflies.
• Quantification of directional and stabilizing selection on male body size.

Main Results:

• Directional selection on male body size occurred when average male and female sizes differed significantly.
• Stabilizing selection was observed when size distributions overlapped and variance was large.
• No significant selection was detected when size distributions overlapped and variance was small.

Conclusions:

• Temporal variation in selection form is explained by concurrent changes in fitness surfaces and phenotype distributions.
• Accounting for both fitness and phenotypic dynamics is essential for accurate inference of selection.
• This study highlights the complexity of evolutionary processes in natural populations.