Do larger individuals cope with resource fluctuations better? An artificial selection approach

Area of Science:

• Ecology
• Evolutionary Biology
• Marine Biology

Background:

• Organism size influences resource acquisition and utilization rates, but optimal size under unpredictable resource conditions remains debated.
• Previous studies relied on interspecific comparisons, confounding body size with other life-history traits.

Purpose of the Study:

• To investigate the direct impact of body size on phytoplankton growth and resource recovery under varying nutrient conditions.
• To test the 'fasting endurance hypothesis' using an experimental evolution approach.

Main Methods:

• Evolved distinct small and large body sizes in *Dunaliella tertiolecta* phytoplankton over 280 generations via artificial selection.
• Assessed growth rates and recovery from nitrogen and phosphorus deprivation in size-selected lineages.

Main Results:

• Smaller phytoplankton lineages displayed slower growth, reduced resource storage, and impaired recovery from phosphorus depletion.
• Recovery from nitrogen limitation was not significantly influenced by body size, contrary to expectations.
• These findings suggest smaller phytoplankton may be less resilient to certain nutrient stresses.

Conclusions:

• Body size plays a crucial role in phytoplankton’s response to nutrient availability, particularly phosphorus.
• The size-independent recovery from nitrogen limitation highlights complexity in phytoplankton adaptation strategies.
• Projected declines in phytoplankton cell size could negatively impact global carbon fixation and primary productivity.