Early Spatiotemporal Deficits Become Competitive Advantages During Collective Expansion.

Area of Science:

• Ecology
• Evolutionary Biology
• Microbiology

Background:

• Rapid spatial expansion is crucial for population persistence and ecological dominance.
• The influence of initial conditions on range expansion outcomes is not fully understood.
• Priority effects classically favor earlier or larger founding populations.

Purpose of the Study:

• To investigate how initial spatiotemporal conditions of founding populations shape range expansion outcomes.
• To determine if collective motility can alter classical priority effects.
• To develop a quantitative framework linking initial population organization to spatial outcomes.

Main Methods:

• Combined nonlinear theory with quantitative microbial experiments.
• Controlled inoculum size and quantified range expansion rates.
• Performed head-to-head competition and laboratory evolution experiments with diverse swarming microbes.

Main Results:

• Collective motility, unlike individual motility, can enable lagging populations to gain a competitive advantage.
• Nonlinear density-dependent feedback drives this reversal of priority effects.
• The advantage is maximized when expansion delay scales log-linearly with initial density, a behavior observed across various microbes.

Conclusions:

• Collective motility provides a regulatory strategy for competitive range expansion, overturning traditional priority effects.
• This behavior is adaptive and robustly maintained through competition and evolution.
• The study establishes a quantitative framework for understanding how initial population dynamics influence ecological success in spatial expansion.