Intraspecific variation and species coexistence.

Area of Science:

• Ecology
• Population Dynamics
• Community Ecology

Background:

• Intraspecific variation, differences within a species, is crucial for understanding ecological dynamics.
• Plant competition models often simplify individual performance, potentially overlooking the role of variation.

Purpose of the Study:

• To investigate how intraspecific variation in competitive ability influences the dynamics of two-species plant communities.
• To determine the conditions under which intraspecific variation promotes or hinders species coexistence.

Main Methods:

• A two-species model of plant competition was developed.
• Individual competitive ability was modeled as a random draw from species-specific distributions.
• The model explored the effects of varying population density and interspecific trade-offs.

Main Results:

• Species with high maximum or variance in performance are favored at high densities, while high mean performance is favored at low densities.
• Interspecific trade-offs in mean-variance performance can stabilize coexistence only within a narrow range of intermediate densities.
• Intraspecific variation can obscure interspecific differences, but this effect weakens with increasing density, potentially leading to rapid extinction of inferior species.

Conclusions:

• Intraspecific variation can facilitate species coexistence, but its importance in maintaining real-world biodiversity may be limited.
• Density-dependent selection on performance variation plays a key role in community assembly.
• The stabilizing effect of interspecific trade-offs is weak and restricted to specific density ranges.