Fertilization Mode Covaries with Body Size.

Area of Science:

• Evolutionary biology
• Marine biology
• Reproductive strategies

Background:

• Internal fertilization has evolved independently multiple times across diverse taxa.
• The evolution of internal fertilization influences sexual selection and traits like testes and gamete size.
• Associations between fertilization mode and non-primary sexual traits remain largely unexplored.

Purpose of the Study:

• To investigate the evolutionary covariance between fertilization mode and adult body size in marine invertebrates.
• To test theoretical predictions that fertilization mode and body size should covary.
• To determine if fertilization mode impacts traits indirectly related to reproduction.

Main Methods:

• A phylogenetically controlled comparative approach was employed.
• Data from 1,232 species of marine invertebrates across three phyla were analyzed.
• Covariance was assessed while controlling for latitude, offspring size, and developmental mode.

Main Results:

• A consistent pattern emerged across all phyla studied: external fertilizers were significantly larger than internal fertilizers.
• The study found a significant negative correlation between internal fertilization and body size.
• These results indicate that fertilization mode has broader evolutionary consequences beyond direct reproductive traits.

Conclusions:

• Fertilization mode is associated with adult body size in marine invertebrates.
• The findings support the hypothesis that body size evolves in conjunction with fertilization strategy.
• This suggests that other, unexplored traits may also coevolve with fertilization mode.