Genetic mixture of multiple source populations accelerates invasive range expansion.

Area of Science:

• Ecology
• Evolutionary Biology
• Genetics

Background:

• Many successful biological invasions originate from multiple genetically distinct populations.
• Understanding the mechanisms by which genetic mixture influences invasiveness is crucial but lags behind observational data.

Purpose of the Study:

• To experimentally test the impact of genetic mixture on the velocity of invasive range expansion.
• To differentiate between evolutionary responses and heterosis as drivers of mixture effects.

Main Methods:

• Laboratory experiment using beetles in artificial landscapes.
• Invasions initiated with one, two, four, or six genetic sources over six generations.
• Quantified range expansion velocity, demography, and dispersal.

Main Results:

• Invasions with genetic mixture (2, 4, or 6 sources) spread farther than single-source invasions over six generations.
• Heterosis (hybrid vigor) provided an initial 'catapult effect' on expansion.
• Genetic mixture positively impacted local demography (reduced extinction, enhanced growth) early in invasion, but not dispersal.

Conclusions:

• Genetic mixture significantly enhances the spatial expansion of invasive species.
• Heterosis, rather than sustained evolutionary change, appears to be the primary driver of this initial expansion boost.
• These findings highlight the importance of considering genetic diversity in predicting and managing biological invasions.