1) Saddleback tortoises are on dry desert-like islands. Domed back turtles are from wetter regions.
2) The original cause of the variation of necks and shells is as the tortoises moved to the different islands the ones that were better suited to live had the suitable body types to survive.
3)The longer necks allowed the tortoises to better reach the vegetation.
4)This tortoise probably lives on an island that is both wet and dry