ALDABRA RAIL (ITERATIVE EVOLUTION)

About: 

• Around 136,000 years ago, the Aldabra atoll in the Indian Ocean was inundated by a major flood that wiped out all the terrestrial animals that lived there including a species of flightless bird called the Aldabra rail.
  
  
• Tens of thousands of years later, sea levels fell back, once again making life possible on the atoll and the once-extinct Aldabra rail came back due to the process of “iterative evolution.”
  
  

Aldabra rail:

• The Aldabra rail is a subspecies of the white-throated rail (Dryolimnas cuvieri), a chicken-sized bird which is indigenous to islands in the southwestern Indian Ocean.
  
  
• The birds are “persistent colonizers”; they are known to build up on large land bodies and subsequently depart en masse, possibly triggered by overcrowding and a lack of food.
  
  
• At some point in the distant past, rails landed on Aldabra. There were no predators on the atoll, rendering the birds’ ability to fly unnecessary—so they lost it.
  
  
• And in the wake of the inundation event, the process happened again: Rails arrived on Aldabra and, faced with a lack of predation, once again lost their flight. The Aldabra rail is, in fact, the only flightless rail that still survives in the Indian Ocean.