Abstract

Parasites such as viruses are often locked in an evolutionary arms race with their hosts. A classic example of reproductive parasitism is the cuckoo, which lays its eggs in the nests of other species, so that adult cuckoos pay none of the costs of incubation or feeding chicks. In defense, many host birds have evolved to recognize mismatched eggs, which in turn selects for striking egg mimicry by cuckoos. I study a similar arms race in an African bird, the cuckoo finch, which has independently evolved to be a reproductive parasite. This parasitic relationship is strikingly older than that between common European cuckoos and their hosts, and so more evolution has occurred in the ongoing arms race between cuckoo finches and their several host species. As a result, I have found that there is an old evolutionary split between female cuckoo finch lineages that specialize on different hosts. Each lineage of cuckoo finches lays eggs that mimic those of a particular host species. Surprisingly, this specialization has not resulted in each parasite lineage evolving into a different species. I am studying the genetic underpinnings of cuckoo finch egg colours and patterns, to test the hypothesis that the genetic differences responsible for egg mimicry are found on the female-specific sex chromosome in birds, thereby enabling females to pass on adaptive genetic instructions to their daughters while interbreeding with males raised by different host species maintains gene flow and prevents speciation.