Genetic depletion does not prevent rapid evolution in island-introduced lizards

Area of Science:

• Evolutionary biology
• Genomics
• Ecology

Background:

• Experimental introductions offer insights into rapid phenotypic change.
• Few studies examine genetic impacts of introductions, including neutral and adaptive processes.
• Wall lizards on Croatian islands provide a model for studying adaptation after introduction.

Purpose of the Study:

• To investigate the genetic basis of rapid phenotypic changes in experimentally introduced wall lizards.
• To differentiate between neutral genetic drift, plasticity, and natural selection in adaptation.
• To understand the evolutionary potential of bottlenecked populations under new selective pressures.

Main Methods:

• Genomic analysis using approximately 82,000 ddRAD loci.
• Comparison of genetic differentiation between introduced and source populations.
• Genome-scan analysis to identify loci under selection.
• Functional annotation of candidate genes.

Main Results:

• Confirmed founder effect and low neutral genetic differentiation between introduced and source populations.
• Observed signals of population expansion and high density despite genetic depletion.
• Identified a small number of loci with significant allelic shifts between ecologically divergent populations.
• Found candidate genes related to diet-induced adaptation.

Conclusions:

• Extreme phenotypic differences are likely driven by a few large-effect genetic loci and/or phenotypic plasticity.
• Bottlenecked populations possess evolutionary potential to adapt rapidly to new environments.
• Directional selection may play a role in diet-induced adaptation, as suggested by candidate genes.