Teranesia - Greg Egan

Welcome to Teranesia, the island of butterflies, where evolution has stopped making sense.
Prabir Suresh lives in paradise, a nine-year-old boy with an island all his own: to name, to explore, and to populate with imaginary creatures stranger than any exotic tropical wildlife. Teranesia is his kingdom, shared only with his biologist parents and baby sister Madhusree. The evolutionary puzzle of the island's butterflies that brought his family to the remote South Moluccas barely touches Prabir; his own life revolves around the beaches, the jungle, and the schooling and friendships made possible by the net.
When civil war breaks out across Indonesia, this paradise comes to a violent end. The mystery of the butterflies remains unsolved, but nearly twenty years later reports begin to appear of strange new species of plants and animals being found throughout the region - species separated from their known cousins by recent, dramatic mutations that seem far too useful to have arisen by chance from pollution, disease, or any other random catastrophe.
Madhusree is now a biology student, proud of her parents' unacknowledged work, and with no memories of the trauma of the war to discourage her, she decides to join a multinational expedition being mounted to investigate the new phenomenon. Unable to cast off his fears for her safety, Prabir reluctantly follows her. But travel between the scattered islands is difficult, and Madhusree has covered her tracks. In the hope of finding her, Prabir joins up with an independent scientist, Martha Grant, who has come to search for both clues to the mystery and whatever commercial benefits it might bring to her sponsor. As Prabir and Martha begin to untangle the secret of Teranesia, Prabir is forced to confront his past, and to face the painful realities that have shaped his life.