Light limitation increases multidimensional trait evenness in phytoplankton populations

Area of Science:

• Ecology
• Microbial Ecology
• Evolutionary Biology

Background:

• Individual variation impacts population dynamics, but its link to species coexistence mechanisms is unclear.
• Previous studies suggested trait evenness increases with resource limitation in lake phytoplankton.
• Resource partitioning at the individual level may explain this pattern.

Purpose of the Study:

• To experimentally test if resource limitation increases trait evenness in phytoplankton.
• To investigate the role of light intensity as a limiting resource.
• To examine trait variation in monocultures and mixed cultures of phytoplankton species.

Main Methods:

• Cultured two phytoplankton species, Pseudokirchneriella subcapitata and Microcystis aeruginosa.
• Exposed cultures to a gradient of light intensity, both individually and jointly.
• Analyzed multidimensional trait space using four pigment-related trait dimensions.

Main Results:

• Low light (resource) conditions led to population diversification into a wide range of phenotypes.
• These phenotypes were evenly distributed in multidimensional trait space.
• This pattern was observed in both monocultures and mixed cultures, consistent with field observations.

Conclusions:

• Resource limitation, specifically light limitation, increases the evenness of microbial phenotypes.
• Individual phytoplankton cells adjust photosynthetic traits to reduce overlap in light acquisition under limitation.
• This trait-based adjustment enhances individual success and advances understanding of species coexistence.