Rapid trait evolution drives increased speed and variance in experimental range expansions.

Area of Science:

• Ecology
• Evolutionary Biology
• Biodiversity Science

Background:

• Range expansions are critical to understanding biological invasions and climate change impacts on biodiversity.
• Traditional models of range expansion focus on demographic processes (birth, death, dispersal), often neglecting evolutionary influences.
• Emerging research suggests rapid evolution can significantly affect expansion rates, but experimental evidence is limited.

Purpose of the Study:

• To experimentally investigate the role of rapid evolution in driving the speed and variability of range expansions.
• To determine how specific evolved traits at the expansion edge influence population spread.

Main Methods:

• Utilized flour beetles (Tribolium castaneum) in controlled experiments to simulate range expansions.
• Compared the expansion dynamics of populations undergoing rapid evolution at the edge with spatially non-evolving controls.
• Measured expansion speed and analyzed evolved traits (dispersal ability, intrinsic growth rates) at the expansion front.

Main Results:

• Rapid evolution at the expansion edge significantly increased both the mean expansion speed and the stochastic variation in speed.
• Populations at the expansion edge evolved higher dispersal ability and lower intrinsic growth rates compared to controls.
• The variability in evolved traits led to increased variance in expansion speed across replicate populations.

Conclusions:

• Evolutionary processes, specifically the rapid adaptation of traits at the expansion edge, are critical determinants of range expansion speed and variability.
• Demographic and evolutionary factors must be integrated for accurate predictions of biodiversity dynamics during range expansions.
• This study provides experimental evidence that evolution can accelerate and destabilize the spread of populations.