Limited spatial separation within small islands suggests that observed population divergence may occur due to habitat differences without interruption to gene flow, but strong evidence of this is scarce. This study examines the Madeiran wall lizard (*Teira dugesii*) inhabiting contrasting beach and inland habitats. Using a matched pairs sampling design across four locations, the researchers found significant morphological and color divergence between beach and inland populations, with beach lizards being darker and having wider snouts. Genotyping-by-sequencing rejected the hypothesis that beach populations form a distinct lineage, while Bayesian analyses strongly supported models incorporating gene flow. The findings reveal how divergence can originate within small islands despite ongoing gene flow.

Richard P. Brown, Yuanting Jin, Jordan Thomas, Carlo Meloro