An integrated analysis of phenotypic selection on insect body size and development time

Area of Science:

• Evolutionary Biology
• Quantitative Genetics
• Ecology

Background:

• Traditional phenotypic selection studies often lack a unified framework to assess multiple fitness components simultaneously.
• This limitation hinders understanding of how selection on traits operates through diverse fitness aspects like survival and reproduction.

Purpose of the Study:

• To introduce and apply a novel generation of aster models for evaluating phenotypic selection considering multiple fitness components.
• To investigate the influence of life-history transition timing on population growth rate, survival, and reproductive output.
• To estimate selection surfaces for body size and development time in a field population of Manduca sexta.

Main Methods:

• Utilized advanced aster models to integrate survival, reproductive output, and the timing of life-history transitions.
• Applied the framework to a field population of Manduca sexta (Lepidoptera: Sphingidae).
• Estimated fitness surfaces to quantify selection gradients for body size and development time.

Main Results:

• Detected strong directional selection favoring larger adult size (via egg counts) and faster early larval development (via larval survival).
• Incorporating reproduction timing and population growth rate modified the estimated optima for size and development time, revealing weaker selection.
• Demonstrated the complex interplay between different fitness components in shaping selection on traits.

Conclusions:

• The integrated aster modeling framework provides a robust method for studying phenotypic selection across multiple fitness components.
• Selection on traits like size and development time is significantly influenced by the timing of life-history events and their impact on population dynamics.
• This approach is readily applicable to diverse systems for a more comprehensive understanding of evolutionary processes.