Butterflies defeat bacteria

Male butterflies in Samoa, almost exterminated 6 years ago due to a deadly bacteria that attacked them, have recovered and returned to a normal population size, and this, according to the researchers, is thanks to rapid selection in favor of a savior gene

Male butterflies in Samoa, almost exterminated 6 years ago due to a deadly bacteria that attacked them, have recovered and returned to a normal population size, and this, according to the researchers, is thanks to rapid selection in favor of a savior gene.

In 2001, the bacterium Wolbachia, which attacks males, left the butterfly population extremely damaged, with 1% of the original male population of the species Hypolimnas bolina. Within five years, the size of the population skyrocketed and returned to its original size, despite the continued attacks of the bacterium.

Wolbachia are gram-negative bacteria that cause heritable intracellular infections in many species of invertebrates. They are very common in 20-75% of known insect species. In addition, they also attack many species that are not insects, such as nematodes, spiders and more. The full range of their surrogates is still unknown. Much of the success of Wolbachia can be attributed to the different phenotypes resulting from infection. These range from classical mutualism to cultural surrogacy, as characterized by the ability of Wolbachia to bypass chromosomal sex determination, to further parthenogenesis, to selectively kill males, to affect the competition between sperm cells and to produce cytoplastic incompatibility in the early stages of the embryo. The unique biology of Wolbachia attracts a growing number of scientists examining a wide range of questions from the evolutionary implications of infection to the possibilities of using Wolbachia in biological control and disease control.

The researchers assume that the insect species did this either through the evolution of a gene that blocks the killing ability of the bacteria or by "acquiring" this gene through breeding with butterflies from a different population. The selection in favor of this gene was so strong that it spread throughout the entire population in less than 10 generations.
The group of researchers reported these findings in the journal Science.

Information about Wolbachia: http://www.wolbachia.sols.uq.edu.au/about.cfm