Predator-Prey Coevolution Drives Productivity-Richness Relationships in Planktonic Systems

Area of Science:

• Ecology
• Evolutionary Biology
• Theoretical Ecology

Background:

• The relationship between environmental productivity and species richness is complex and varies across studies.
• Explanations for these varying productivity-richness relationships remain elusive.
• Coevolutionary dynamics are hypothesized to play a role.

Purpose of the Study:

• To investigate how phytoplankton and zooplankton coevolution influences productivity-richness relationships.
• To model the impact of size-dependent metabolic rates on evolutionary outcomes.
• To compare evolved species richness across different productivity levels and evolutionary timescales.

Main Methods:

• Utilized a simple nutrient-phytoplankton-zooplankton model.
• Incorporated size-dependent metabolic rates derived from empirical data.
• Simulated evolutionary branching under varying productivity scenarios.

Main Results:

• Disruptive selection resulted in evolutionary branching for both phytoplankton and zooplankton.
• Increased productivity accelerated the time to evolutionary branching and the number of evolved species.
• Observed transient unimodal or positive productivity-richness relationships, followed by positive relationships over longer evolutionary times.

Conclusions:

• Coevolution between phytoplankton and zooplankton can generate both unimodal and positive productivity-richness relationships.
• Model findings align with common patterns observed in natural ecosystems.
• Highlights the importance of considering coevolutionary processes in ecological dynamics.