Galápagos Hawks Hand Down Lice Like Family Heirlooms, Study Finds

A Galápagos hawk nesting on Isla Fernandina, Galapagos. (Photo by Noah Whiteman)
A Galápagos hawk nesting on Isla Fernandina, Galapagos. (Photo by Noah Whiteman)

Say what you will about the parasitic lifestyle, but in the game of evolution, it's a winner.

Given that about half of all known species are parasites, biologists have long hypothesized that the strategy of leeching off other organisms is a major driver of biodiversity. Studying populations of Galápagos hawks (Buteo galapagoensis) and feather lice that live in their plumage (Degeeriella regalis), a group led by University of Arizona ecologists and evolutionary biologists has gathered some of the first field evidence suggesting that a phenomenon called co-divergence between parasites and hosts is indeed an important mechanism driving the evolution of biodiversity.

"The idea is really simple," said the study's lead author, Jennifer Koop, who is a postdoctoral fellow in the lab of Noah Whiteman in the UA's Department of Ecology and Evolutionary Biology. "Each time a host population splits into separate populations that potentially become different species, we predict that their parasites could do the same thing."

However, biologists have long struggled to test this hypothesis, as parasites are elusive.

"Often, the evolutionary trees of parasites and their hosts are congruent – they look like mirror images of one another," said Whiteman, who is an assistant professor in EEB, a joint assistant professor in the Department of Entomology and the School of Plant Sciences, and a member of the UA's BIO5 Institute. "But because parasites tend to be inside or attached to hosts, their distributions are difficult to study."

"We found the lice are passed on from mother to babies during brooding, almost like genes," Whiteman said. "They're evolutionary heirlooms, like your family's silverware or engagement ring diamond."

Because the hawks pass on the feather lice from generation to generation, the researchers wanted to know whether the louse populations diverge between populations of hawks and between individual hawks, or whether the populations of the birds and the lice diverged independently of each other.

Read the rest of this August 6, 2014 UANews article at the link below.

Date released: 
Aug 18 2014