Sunday, February 17, 2008

Male Killer

A really nice story from UC Berkeley last year shows natural selection in action and illustrates the Red Queen principle.

Wolbachia is a is a genus of inherited bacterium that infects a high proportion of all insects. They are the world's most common parasitic microbes and often lead to the death of males.

Over only 10 generations that spanned less than a year, the proportion of males of the Hypolimnas bolina butterfly on the South Pacific island of Savaii jumped from 1 percent of the population to about 39 percent. The researchers considered this a stunning comeback and credited it to the rise of a suppressor gene that holds in check the Wolbachia bacteria, which is passed down from the mother and selectively kills males before they have a chance to hatch.

"To my knowledge, this is the fastest evolutionary change that has ever been observed. This study shows that when a population experiences very intense selective pressures, such as an extremely skewed sex ratio, evolution can happen very fast."
Sylvain Charlat

The fieldwork for this study was carried out on two South Pacific Islands and the researchers were based out of UC Berkeley's Richard B. Gump South Pacific Research Station on the island of Moorea in French Polynesia. I mention this because although the field station is run by Berkeley, UC Santa Barbara runs the Moorea Coral Reef Long Term Ecological Research Program and there are plenty of opportunities to get involved in this research if that is where your interests take you.

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