Founder Effects Persist Despite Adaptive Differentiation: A Field Experiment with Lizards

Abstract

Random and Directed Natural selection drives populations to adapt to new environments; the raw material or “founder effects” provided by the first colonizing individuals can thus have a formative influence on the population's future. Kolbe et al. (p. 1086 , published online 2 February; see the cover) tested the relative contributions of selection and founder effects in Bahamian lizards. Founders were taken from an island covered in forest: These lizards had long hindlimbs for sprinting across the broad expanses of tree trunks. Long-limbed lizards were introduced to seven smaller islands covered in scrub that, before hurricane Frances in 2004 swept them away, had been populated by lizards with short hindlimbs better suited for navigating a twiggy habitat. After several generations, all the new lizard populations had adapted to their new habitats by evolving shorter hindlimbs but they also retained other morphological and genetic signatures from their founding ancestors. Thus, evolution occurs by a combination of arbitrary events, as well as those shaped by selection.