An alpine plant shows no decrease in genetic diversity associated with rapid post-glacial range expansion

Area of Science:

• Ecology
• Evolutionary Biology
• Genetics

Background:

• Range expansion is a key species survival strategy under climate change.
• Eco-evolutionary models predict decreased genetic diversity and fitness at the expanding range edge due to genetic drift.
• These predictions are based on dispersal from the leading edge, a pattern observed in past continental-scale expansions but less studied in contemporary, smaller-scale events like alpine glacier recession.

Purpose of the Study:

• To investigate genetic diversity and differentiation patterns during contemporary range expansion in alpine environments.
• To test eco-evolutionary model predictions of decreased genetic variation and increased differentiation at the leading edge of species' ranges.
• To assess the applicability of established range expansion theories to recent, smaller-scale colonization events.

Main Methods:

• Studied the alpine plant Erythranthe (Mimulus) lewisii undergoing range expansion on glacier forelands.
• Quantified neutral genetic diversity using single nucleotide polymorphisms (SNPs).
• Inferred signatures of genetic drift by comparing genetic differentiation and variation between the historical range core and the contemporary range edge over space and time.

Main Results:

• Found weak evidence for increased genetic differentiation towards the expanding range edge.
• Observed no significant decrease in genetic diversity towards the range edge.
• Results indicate that dispersal is not exclusively from the leading edge during this type of colonization.

Conclusions:

• Demographic processes during colonization of areas revealed by alpine glacier retreat do not lead to a loss of genetic diversity over space and time.
• The findings suggest that theoretical predictions of reduced range-edge fitness due to range expansion may not apply to contemporary alpine colonization.
• Contemporary alpine range expansions may involve different dispersal dynamics than those seen in historical, large-scale expansions.