In their study, Klimov and OConnor evaluated all 62 hypotheses. Their project used large-scale DNA sequencing, the construction of detailed evolutionary trees called phylogenies, and sophisticated statistical analyses to test the hypotheses about the ancestral ecology of house dust mites.
On the phylogenetic tree they produced, house dust mites appear within a large lineage of parasitic mites, the Psoroptidia. These mites are full-time parasites of birds and mammals that never leave the bodies of their hosts. The U-M analysis shows that the immediate parasitic ancestors of house dust mites include skin mites, such as the psoroptic mange mites of livestock and the dog and cat ear mite.
"This result was so surprising that we decided to contact our colleagues to obtain their feedback prior to sending these data for publication," said Klimov, the first author of the paper and an assistant research scientist in the Department of Ecology and Evolutionary Biology.
The result was so surprising largely because it runs counter to the entrenched idea that highly specialized parasites cannot return to the free-living lifestyle of their ancestors.
"Parasites can quickly evolve highly sophisticated mechanisms for host exploitation and can lose their ability to function away from the host body," Klimov said. "They often experience degradation or loss of many genes because their functions are no longer required in a rich environment where hosts provide both living space and nutrients. Many researchers in the field perceive such specialization as evolutionarily irreversible."
The U-M findings also have human-health implications, said OConnor, a professor in the Department of Ecology and Evolutionary Biology and a curator of insects and arachnids at the U-M Museum of Zoology.
"Our study is an example of how asking a purely academic qu
|Contact: Jim Erickson|
University of Michigan