QUANTITATIVE GENETICS OF SPRINT RUNNING SPEED AND SWIMMING ENDURANCE IN LABORATORY HOUSE MICE (MUS DOMESTICUS)

Area of Science:

• Evolutionary biology
• Quantitative genetics
• Animal physiology

Background:

• Locomotor performance, including speed and endurance, is crucial for survival and reproduction in wild populations.
• Understanding genetic correlations between different fitness-related traits can reveal evolutionary constraints.

Purpose of the Study:

• To test the hypothesis of a negative genetic correlation between locomotor speed and endurance in house mice.
• To investigate the genetic correlation of speed and endurance with body mass.

Main Methods:

• Utilized a genetically variable laboratory strain of house mice (Hsd:ICR: Mus domesticus).
• Employed quantitative genetic parameter estimation using restricted maximum-likelihood (REML) methods, incorporating cross-fostering.
• Controlled for confounding variables like age, measurement block, observer, and sex through residual analysis.

Main Results:

• A significant negative additive genetic covariance was found between locomotor speed and endurance.
• Heritability estimates for endurance were moderate (0.17–0.33), while heritability for sprint speed was low and inconsistent across trials.
• No significant genetic correlations were detected between speed or endurance and body mass.

Conclusions:

• A negative genetic correlation between speed and endurance suggests an evolutionary constraint, potentially limiting simultaneous improvement in both traits.
• Artificial selection for increased locomotor speed is predicted to result in decreased endurance.
• Body mass is unlikely to be a significant factor in the trade-off between locomotor speed and endurance.