Remarkably, the findings, which are published in the journal Biology Letters of the Royal Society, revealed that the population structure of the lice matched that of the birds across the archipelago, even though the two are very different species.
"To the lice, each bird is an island, and their populations are very different from bird to bird," Whiteman said. "The same pattern is repeated between bird populations on different islands. It's like Russian dolls."
In other words, the lice living on any one bird and its offspring are more closely related than the lice living on a different bird. As the birds diversify into distinct populations on each island, their parasites diversify with them. The findings help explain the rapid rate of parasite evolution, according to the research team.
"You have to be in the right spot at the right time to see this process happening," Koop said. "Our study empirically demonstrates an important evolutionary process in which the hawks separate into different populations, and the lice living on them do the same."
This process is hypothesized to lead to the formation of different species, in this case different species of hawks and lice, and may explain some of the extraordinary diversity seen among parasites, she said.
The team chose the Galpagos Islands, located 575 miles off the west coast of Ecuador, for the study because the species that colonized the geologically young group of islands have evolved in isolation, making the area an ideal natural laboratory.
"Of all the vertebrate species native to the Galpagos, the Galpagos hawk is the most recent arrival," Whiteman said. "So whatever is happening in terms of evolution of the bird population and the parasite population is most likely in the earliest stages of that process."
In four years
|Contact: Daniel Stolte|
University of Arizona