The relationship between offspring size and performance in the sea

Area of Science:

• Marine Biology
• Evolutionary Ecology
• Quantitative Biology

Background:

• Offspring size variation historically explained population differences, with less focus on within-population scales.
• Offspring size variation is often considered an adaptive trait, but direct empirical tests are scarce.

Purpose of the Study:

• To investigate the spatial and temporal scales of offspring size variation in the marine invertebrate Watersipora subtorquata.
• To test if offspring size variation is adaptive by linking it to offspring performance across different populations and times.
• To model optimal offspring size predictions based on observed relationships between offspring size and performance.

Main Methods:

• Partitioning natural variation in offspring size across spatial and temporal scales in southeastern Australia.
• Estimating the relationship between offspring size and performance at the population level for each sampling time.
• Utilizing an optimality model parameterized with empirical data to predict offspring size.

Main Results:

• Significant offspring size variation was observed among populations, but regional factors explained only ~25% of this variation.
• Local population and temporal factors were more influential on offspring size variation than broad regional differences.
• Differences in the offspring size-performance relationship across populations and times correlated with observed offspring sizes.

Conclusions:

• Interpopulation variation in offspring size can be an adaptive strategy responding to local environmental conditions.
• The optimal offspring size is not static but is dynamically influenced by local factors.
• Future research should prioritize understanding small-scale variation in offspring size for a comprehensive view of adaptive strategies.