New study sheds light on Galápagos hawk evolutionary history

Oct 02, 2007

Scientists at the University of Missouri-St. Louis used DNA sequences from feather lice to study how island populations of their host, the Galápagos Hawk might have colonized the Galápagos islands, home to the endangered and declining raptor.

The study, recently published online in the journal Molecular Ecology, focuses on genes from three parasite species restricted to the Galápagos 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 parasite’s mitochondrial DNA was more variable than the host’s, the parasite’s family tree revealed how four of the hawk’s 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 hawk’s 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 hawk’s DNA. The rapidly evolving lice that live their entire lives on these birds have helped illuminate their host’s evolutionary history.”

The Galápagos National Park and Charles Darwin Research Station are working to save Darwin’s archipelago from the fate of similar island systems. As part of this effort Patricia Parker, the E. Desmond Lee Professor of Zoological Studies at UMSL, forged a close working relationship with the two organizations to better understand the threats facing the island’s endangered birds. Parker initiated this collaboration by examining the basic biology and conservation genetics of the Galápagos Hawk and a few other species that she and her collaborators had studied previously.

A permanent resident found only in the Galápagos island, the Galápagos hawk has intrigued biologists for decades because of its unusual mating system, (cooperative polyandry) within some, but not all, island populations.

In this type of mating system, a single female hawk and up to eight male hawks, who are not close relatives, live in a stable territorial group and cooperate to rear chicks. This type of mating system is rare among birds, and understanding the sequence in which islands were colonized may reveal the point at which it first occurred, and thereby help us understand the evolution of cooperative behavior.

Source: Blackwell Publishing Ltd.

Explore further: Compact wool measurement tool may find home on the range

add to favorites email to friend print save as pdf

Related Stories

Arsenic stubbornly taints many US wells, say new reports

47 minutes ago

Naturally occurring arsenic in private wells threatens people in many U.S. states and parts of Canada, according to a package of a dozen scientific papers to be published next week. The studies, focused mainly ...

Planck: Gravitational waves remain elusive

1 hour ago

Despite earlier reports of a possible detection, a joint analysis of data from ESA's Planck satellite and the ground-based BICEP2 and Keck Array experiments has found no conclusive evidence of primordial ...

Evidence mounts for quantum criticality theory

3 hours ago

A new study by a team of physicists at Rice University, Zhejiang University, Los Alamos National Laboratory, Florida State University and the Max Planck Institute adds to the growing body of evidence supporting ...

Recommended for you

Population genomics unveil seahorse domain

6 hours ago

In a finding vital to effective species management, a team including City College of New York biologists has determined that the lined seahorse (Hippocampus erectus) is more a permanent resident of the we ...

Researchers develop new potato cultivar

9 hours ago

Dakota Ruby is the name of a new potato cultivar developed by the NDSU potato breeding project and released by the North Dakota Agricultural Experiment Station. Dakota Ruby has bright red skin, stores well and is intended ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.