Species range expansion by beneficial mutations

Area of Science:

• Evolutionary biology
• Ecology
• Population genetics

Background:

• Species' geographic ranges are limited by their ability to adapt to environmental extremes.
• Genetic variation is crucial for adaptation, but its role in range expansion is complex.
• Understanding range expansion mechanisms is vital for predicting species' responses to climate change.

Purpose of the Study:

• To investigate how new mutations facilitate range expansion in continuous populations.
• To determine the influence of environmental gradients and population growth rates on mutation establishment and range expansion.
• To compare the effects of sexual versus asexual reproduction on range expansion dynamics.

Main Methods:

• Simulations were used to model the establishment probabilities of new mutations affecting quantitative traits.
• The study considered spatially varying optimal phenotypes and linear environmental gradients.
• Population growth rates and reproductive modes (sexual vs. asexual) were incorporated into the models.

Main Results:

• Shallow environmental gradients favored mutations arising near the range margin with smaller phenotypic effects, resulting in larger range expansions.
• Steeper gradients favored mutations with larger phenotypic effects.
• High population growth rates led to mutations originating closer to the range edge but smaller relative range expansions.
• Sexual reproduction facilitated larger range expansions and adaptation to more extreme environments compared to asexual reproduction.

Conclusions:

• New mutations with significant phenotypic effects ( > 1 SD) are key drivers of substantial range expansion (≥15%).
• Environmental gradient steepness and population growth rates critically influence the characteristics of successful mutations and the extent of range expansion.
• Sexual reproduction offers a significant advantage for range expansion and adaptation in novel environments.