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: Scientists create mouse model to accelerate research on Ebola vaccines, treatments

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

Researchers capture picture of microRNA in action

Oct 30, 2014

Biologists at The Scripps Research Institute (TSRI) have described the atomic-level workings of "microRNA" molecules, which control the expression of genes in all animals and plants.

Blocking a fork in the road to DNA replication

Oct 30, 2014

A team of Whitehead Institute scientists has discovered the surprising manner in which an enigmatic protein known as SUUR acts to control gene copy number during DNA replication. It's a finding that could shed new light on ...

Cell division, minus the cells

Oct 30, 2014

(Phys.org) —The process of cell division is central to life. The last stage, when two daughter cells split from each other, has fascinated scientists since the dawn of cell biology in the Victorian era. ...

A new method simplifies the analysis of RNA structure

Oct 30, 2014

To understand the function of an RNA molecule, similar to the better-known DNA and vital for cell metabolism, we need to know its three-dimensional structure. Unfortunately, establishing the shape of an RNA ...

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.