Ontogenetic patterns in heritable variation for body size: using random regression models in a wild ungulate...

Area of Science:

• Evolutionary biology
• Quantitative genetics
• Animal ecology

Background:

• Body size is a key factor in organismal fitness.
• Heritable traits can change in importance throughout an individual's life (ontogeny).
• Understanding genetic and environmental influences on size development is crucial for evolutionary studies.

Purpose of the Study:

• To estimate genetic and environmental covariance structures for bighorn sheep June weight over 5 years.
• To assess the effectiveness of random regression models for these estimations.
• To investigate ontogenetic variation in heritability and genetic correlations for body size.

Main Methods:

• Utilized random regression models to analyze longitudinal data on bighorn sheep (Ovis canadensis) weight.
• Estimated additive genetic, maternal genetic, and environmental variances and covariances.
• Calculated heritability and genetic correlations across ontogeny (ages 0-5 years).

Main Results:

• Additive genetic variance for June weight was significant, with heritability increasing over ontogeny.
• Environmental variance decreased with age, contributing to the rising heritability.
• Maternal genetic effects were important for early ages (0-1) but diminished by age 2.
• Strong positive genetic correlations were found between age-specific June weights.
• Random regression models provided results comparable to traditional methods.

Conclusions:

• Heritability of body size in bighorn sheep increases during early development, likely due to viability selection.
• Maternal effects play a significant role in early-life weight but are transient.
• Selection on body size at any developmental stage will have correlated effects on size throughout ontogeny.
• Random regression models offer an efficient approach for estimating genetic parameters in longitudinal studies with incomplete data.