Scientists at the University of Missouri-St. Louis used DNA sequences from feather lice to study how island populations of their host, the Galpagos Hawk might have colonized the Galpagos islands, home to the endangered and declining raptor.
The study, recently published online in the journal Molecular Ecology (www.blackwell-synergy.com/doi/abs/10.1111/j.1365-294X.2007.03512.x), focuses on genes from three parasite species restricted to the Galpagos Hawk. The scientists also sequenced the same genes in the hawk to compare levels of genetic variation across these distantly related species. They traced the family tree of each species across the eight-island range, which were each colonized by the hawks and its parasites.
Because the parasites mitochondrial DNA was more variable than the hosts, the parasites family tree revealed how four of the hawks eight populations were related to one another -- the stepping-stone manner in which, over time, the hawks colonized first one island, then another and another, carrying their lice as they went. These relationships were previously obscured due to the hawks low genetic variation.
The scientists also suggested that their results demonstrate how symbionts of larger and more charismatic species, like hawk lice, can tell scientists a great deal about the history of life.
The parasites are evolutionary heirlooms that were brought to the islands during the colonization of the hawk, but have continued to evolve along with their hawk hosts, said Noah Whiteman, who conducted this study as part of his dissertation at UMSL and is now a postdoctoral fellow at Harvard University in Cambridge, Mass. We had a great deal of trouble understanding how the island populations of the hawk were related to one another because of low genetic variation in the hawks DNA. The rapidly evolving lice that live their entire li
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