Evolutionary biologists have long recognized that molecular evolution proceeds in a largely clock-like manner, with mutations accumulating at a fairly constant rate over time. This "molecular clock" allows for powerful inferencesfrom dating the origins of species to the origins of epidemics. However, the rate at which the clock ticks varies dramatically among species; much research has focused on what causes these differences.
For RNA viruses such as rabies, understanding the rate variability has practical implications, since faster evolution can enable viral emergence in new species or allow a virus to evade its host's immune defenses. However, nearly all past studies compared viruses of completely different families and were therefore limited to focusing on viral structural traits. Since few opportunities existed to study the evolution of similar viruses in different host species, the role of the host had been almost completely neglected.
Streicker set out to better understand the tempo of the evolution of rabies viruses in bats, and specifically what, if any, role the host species played.
To conduct the study, Streicker and his colleagues compiled a database of rabies virus genetic sequences from infected bats in the U.S. and South America, representing 21 different variants of the virus. They also collected information on the biology and ecology of the different bat species that served as viral hosts. They looked at the evolutionary history of the different bat species; their overwintering behavior (whether the bats hibernated, went through periods of torpor or remained active during the winter); their metabolic rates; and their migration habits (whether they engaged in long distance migration). They also classed the bats by climatic region and whether they were solitary or roosted in colonies.
Their analysis of this enormous database revealed extreme var
|Contact: Daniel Streicker|
University of Georgia