Maternal effects and the response to selection in red squirrels

Area of Science:

• Evolutionary biology
• Behavioral ecology
• Quantitative genetics

Background:

• Maternal effects, where mothers influence offspring traits, are theoretically predicted to alter evolutionary dynamics.
• These predictions have rarely been tested empirically in natural populations.
• Understanding maternal effects is crucial for predicting evolutionary trajectories.

Purpose of the Study:

• To empirically test the predictions of maternal effect evolution models in a wild population.
• To quantify the contribution of maternal genetic effects to offspring trait evolution.
• To investigate the role of past selection in current evolutionary responses.

Main Methods:

• Studied natural selection episodes in a wild red squirrel population (Tamiasciurus hudsonicus).
• Quantified changes in juvenile growth rates across generations.
• Analyzed the influence of current and previous generation selection on evolutionary responses.

Main Results:

• Offspring growth rate changes were five times greater than predicted by heritability (h2) alone, indicating significant maternal genetic effects.
• Evolutionary responses to selection were influenced by selection in both the current and previous generations, demonstrating evolutionary momentum.
• Results align with models incorporating maternal effects, such as litter size.

Conclusions:

• Provides the first empirical evidence for the importance of maternal effects in driving evolutionary dynamics in a natural population.
• Highlights that maternal genetic effects can substantially amplify evolutionary responses to selection.
• Demonstrates that evolutionary momentum, influenced by past selection, is a key factor in natural populations.