Interspecific patterns of phenotypic selection do not predict intraspecific patterns

Area of Science:

• Evolutionary Biology
• Ecology
• Quantitative Genetics

Background:

• Phenotypic selection quantifies how traits influence survival and reproduction.
• Previous studies suggest sample size influences estimates of selection gradients (β and γ).
• Host plant-mediated selection is a key driver of insect evolution.

Purpose of the Study:

• To estimate linear (β) and nonlinear (γ) selection gradients on gall size in the wasp Belonocnema treatae.
• To investigate the relationship between subpopulation sample size and selection gradient estimates within this species.
• To test if intraspecific patterns of selection variation align with interspecific patterns related to sample size.

Main Methods:

• Estimated linear and nonlinear selection gradients for gall size across 22 subpopulations.
• Analyzed the correlation between subpopulation sample size and the magnitude/variance of selection gradients.
• Compared observed intraspecific patterns with established interspecific patterns of selection and sample size.

Main Results:

• Intraspecific patterns of phenotypic selection (β and γ) in relation to sample size were not predicted by interspecific patterns.
• The magnitude and variance of selection gradients did not consistently decrease with increasing sample size within the species.
• Biological variation in selection among subpopulations appeared more influential than variation in study size.

Conclusions:

• When selection is heterogeneous across populations, the biological basis of selection is a primary driver of estimates.
• Interspecific patterns regarding sample size and selection gradients do not reliably predict intraspecific dynamics.
• Studying selection within populations is crucial for understanding the sources of variation in evolutionary pressures.