Strong and parallel salinity-induced phenotypic plasticity in one generation of threespine stickleback

Area of Science:

• Evolutionary biology
• Ecology
• Genetics

Background:

• Phenotypic plasticity is crucial for organismal variation but its evolutionary role is debated.
• The threespine stickleback (Gasterosteus aculeatus) provides a model for rapid adaptive radiation due to repeated freshwater invasions.
• Understanding plasticity in sticklebacks can illuminate mechanisms of rapid evolutionary change.

Purpose of the Study:

• To investigate phenotypic plasticity in threespine stickleback body shape in response to salinity.
• To determine if plasticity contributes to the rapid parallel phenotypic changes observed in stickleback adaptive radiations.
• To explore potential evolutionary constraints on plastic phenotypic change.

Main Methods:

• A split-clutch design was used with fish from a wild freshwater population.
• Sticklebacks were raised in different salinity treatments for one generation.
• Body shape was analyzed to quantify plastic responses and allometric relationships.

Main Results:

• Significant and parallel plastic changes in body shape were observed after one generation.
• Fish in saltwater developed shallower bodies and longer jaws compared to freshwater controls.
• Allometric relationships between traits and body size remained consistent across salinity treatments, suggesting constraints.

Conclusions:

• Threespine sticklebacks possess a substantial capacity for plastic phenotypic change in response to salinity.
• Both phenotypic plasticity and evolutionary constraints likely played roles in the diversification of stickleback populations.
• This study highlights the interplay between plasticity and constraints in driving rapid adaptive evolution.