What Need for Speed? Lizards from Islands Missing Predators Sprint Slower

Island taxa are frequently susceptible to introduced predators. This susceptibility is thought to be caused by the loss of key ancestral antipredator physiological adaptations during long periods of evolution under reduced predation pressures. Here, we test the hypothesis that island species have reduced locomotor abilities. While locomotor abilities are critical for escaping predation, little is known on how the presence of different types of native predators influences these abilities by maintaining selective pressure. To fill this gap, we documented sprint speed in the Aegean wall lizard (Podarcis erhardii) from the Aegean islands (Greece) with varying levels of predation pressure. We show that lizards from islands where mammalian predators were present sprinted fastest. Lizards sprinted at an intermediate speed where predators other than mammals were present, and lizards sprinted slowest on islands where no predators were present. Longer periods of evolutionary isolation in island environments were also associated with diminished sprinting speeds. These results indicate that lizards from the lowest-predation islands are the most vulnerable and preventing the introduction of invasive predators should be prioritized for these island systems.