An experimental test of the growth rate hypothesis as a predictive framework for microevolutionary adaptation

Area of Science:

• Ecology
• Evolutionary Biology
• Limnology

Background:

• The growth rate hypothesis (GRH) links organism phosphorus content to growth rate, supported by interspecific data.
• Understanding microevolutionary shifts in consumer stoichiometry is crucial for ecological predictions.

Purpose of the Study:

• To test the applicability of the GRH in predicting microevolutionary changes in body stoichiometry.
• To investigate how different phosphorus availability environments influence evolutionary responses to selection for rapid population growth rate.

Main Methods:

• Selection experiments were conducted on Brachionus calyciflorus populations under phosphorus-rich (HPF) and phosphorus-poor (LPF) conditions.
• Common garden transplant experiments were used to assess evolved changes in relative phosphorus content and population growth rate (PGR).

Main Results:

• Populations selected for increased PGR in HPF environments evolved higher relative phosphorus content, supporting the GRH.
• Populations selected for increased PGR in LPF environments evolved higher PGR without a significant increase in relative phosphorus content.
• Cryptic evolution influenced population performance in response to elemental limitation.

Conclusions:

• The GRH can predict microevolutionary changes in body stoichiometry, but its effectiveness is dependent on the environmental context, specifically nutrient availability.
• Environmental conditions modulate the evolutionary response, highlighting the importance of considering resource stoichiometry in ecological and evolutionary studies.