WQ4. Coevolution of Central American ants in the Pseudomyrmex ferrugineus group and swollen- thorn acacias (Vachellia species) is a type of ____, because _____. Group of answer choices adaptation; the Vachellia species develop swollen thorns for the ants to eat. mutualism; ants receive nesting space in the form of swollen thorns and food from nectaries and leaf-tip food bodies, and Vachellia trees receive protections from ants by removing or repelling herbivores and competing plants. natural selection; ants find the swollen thorn of Vachellia perfect nesting space. mosaic; ants damage the swollen thorn of Vachellia while nesting and the trees kill the ants with their sharp thorns..