Evolution: Lizards get to grips with natural selection

Natural disasters such as hurricanes can have devastating effects on ecosystems, leading to large-scale mortality. It has been unclear, however, whether deaths from hurricanes are indiscriminate, or whether they act to preferentially select for certain physical attributes - such as the ability to resist gale-force winds.

Colin Donihue and colleagues had coincidentally just finished studying populations of small-bodied anole lizards (Anolis scriptus) on the adjacent West Indies islands of Pine and Water Cay before the unexpected landfalls of Hurricanes Irma and Maria. As this was a rare opportunity to study the direct impact of the hurricanes, the authors returned after the storms for a follow-up survey. They studied the difference in limb length and toepad surface area of the populations before and after the hurricane, both of which are believed to affect clinging ability among anoles and be related to habitat use and locomotion style. The surviving lizard populations on both islands had significantly larger toe pads, longer forelimbs and shorter hind limbs on average than before the storms.

The authors also confirmed the link between toe pad size and clinging capability among A. scriptus, and illustrated how the lizards grip branches by filming them being buffeted by hurricane-force winds. Although longer forelimbs afford a better grip; the authors suggest that because of the posture that the lizards adopt when flapping in the wind, having longer back legs would be a disadvantage, as they increase the surface area that is blowing around in the wind.

With extreme climate events predicted to grow in frequency and intensity over the coming decades, the authors conclude that our understanding of evolutionary dynamics will need to factor in such severe selective spells.

Please note that there is an accompanying Nature Video about this research, which is now available on the Nature Research press site.

doi: 10.1038/s41586-018-0352-3

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