Malaria mosquito groups surprisingly do mix and match, new study finds

Nov 27, 2013
Researchers rethinking malaria mosquitos
The study found that the African malaria mosquito Anopheles gambiae has significant exchange of genes between the two groups. Credit: Anthony "Anton" Cornel/UC Davis

(Phys.org) —A new study by researchers at the University of California, Davis, and in Mali finds that many of the assumptions underlying current thinking about the genetics of two key subgroups of malaria mosquitoes are false.

For the past decade, scientists around the world have intensely studied the two forms of the African , Anopheles gambiae. It was thought that the mosquitoes in the two subgroups—known as the M and S forms—rarely mated outside of their groups, and, just this year, the two were recognized as distinct species.

The new study shows, however, that although the M and S subgroups have developed distinct genetic profiles, there actually continues to be significant exchange of genes between the two groups due to crossbreeding. These findings appear online in the Nov. 19 Early Edition of the Proceedings of the National Academy of Sciences.

Developing an accurate picture of gene flow through matings within and between these two mosquito groups could prove key to preventing the spread of . The deadly mosquito-transmitted disease annually kills more than 660,000 people around the world, mostly in Africa.

In this study, lead authors Gregory Lanzaro and Yoosook Lee, both medical entomologists in the UC Davis School of Veterinary Medicine, and their colleagues showed that hybridization, or mating, between the M and S groups was far higher than previously assumed.

"It is critical that we understand the movement of genes between these two forms of the African malaria mosquito," Lanzaro said.

He and Lee noted that researchers need to know whether genes for traits like insecticide resistance are shared between the two malaria mosquito subgroups. This information also is important because some of the techniques that appear to be most promising for controlling malaria involve the movement of genes from genetically modified mosquitoes into natural mosquito populations.

The researchers added that the findings also are significant for evolutionary biologists, confirming that the malaria mosquito is a good model for studying between groups, as well as how species evolve.

The new results show that the frequency of hybrid, or crossbred, individuals in a population ranges from 5 percent to 97 percent, compared to the earlier estimates of less than one percent. Although the M and S hybrids generated in the laboratory are normal in every sense, the new study demonstrates that this is not true in nature, where hybrids are common but less fit than other mosquitoes.

The study included data gathered during 21 years from a single village in Mali. The data, representing approximately 250 mosquito generations, revealed that mating behaviors were temporarily unstable. For example, in one year, the rate of crossbreeding between the two groups jumped from the usual zero percent to 12 percent.

Analysis of the distribution of M and S genetic variations at three regions of the genome demonstrated that strong genetic selection prevented transfer of two of the three regions from one group to the other. However, one region of the genome successfully crossed the reproductive barrier from the S subgroup into the M subgroup. This region presumably contained a gene or genes beneficial to the M form mosquitoes.

Explore further: Top Japan lab dismisses ground-breaking stem cell study

More information: Yoosook Lee, Clare D. Marsden, Laura C. Norris, Travis C. Collier, Bradley J. Main, Abdrahamane Fofana, Anthony J. Cornel, and Gregory C. Lanzaro. "Spatiotemporal dynamics of gene flow and hybrid fitness between the M and S forms of the malaria mosquito, Anopheles gambiae." PNAS 2013 ; published ahead of print November 18, 2013,

Related Stories

Scientists engineer mosquito immune system to fight malaria

Dec 22, 2011

Researchers at the Johns Hopkins Malaria Research Institute have demonstrated that the Anopheles mosquito's innate immune system could be genetically engineered to block the transmission of malaria-causing parasites to humans. ...

New molecular target for malaria control identified

Oct 29, 2013

A new study led by Harvard School of Public Health (HSPH) and University of Perugia (UNIPG) researchers has shown that egg development in the mosquito species primarily responsible for spreading malaria depends ...

Recommended for you

Top Japan lab dismisses ground-breaking stem cell study

Dec 26, 2014

Japan's top research institute on Friday hammered the final nail in the coffin of what was once billed as a ground-breaking stem cell study, dismissing it as flawed and saying the work could have been fabricated.

Research sheds light on what causes cells to divide

Dec 24, 2014

When a rapidly-growing cell divides into two smaller cells, what triggers the split? Is it the size the growing cell eventually reaches? Or is the real trigger the time period over which the cell keeps growing ...

Locking mechanism found for 'scissors' that cut DNA

Dec 24, 2014

Researchers at Johns Hopkins have discovered what keeps an enzyme from becoming overzealous in its clipping of DNA. Since controlled clipping is required for the production of specialized immune system proteins, ...

Scrapie could breach the species barrier

Dec 24, 2014

INRA scientists have shown for the first time that the pathogens responsible for scrapie in small ruminants (prions) have the potential to convert the human prion protein from a healthy state to a pathological ...

Extracting bioactive compounds from marine microalgae

Dec 24, 2014

Microalgae can produce high value health compounds like omega-3s , traditionally sourced from fish. With declining fish stocks, an alternative source is imperative. Published in the Pertanika Journal of Tr ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.