Mating with the wrong insect may cut yellow fever mosquito populations

In a study published this month in the journal Infection, Genetics and Evolution, Post-doctoral Researcher Irka Bargielowski led a team of scientists that conducted field studies in Houston, Texas; Caracas, Venezuela; Franceville, Gabon and Singapore, Malaysia.

They studied mating between the Asian tiger and yellow fever mosquitoes and found that it in the wild, avoidance mechanisms evolved in yellow fever mosquitoes, Bargielowski said. That finding may help scientists predict population changes of the two mosquito populations.

In the current study, about 1 to 3 percent of the mosquitoes mated in the wild, said Bargielowski, who works at the UF/IFAS Florida Medical Entomology Laboratory in Vero Beach.

"Model predictions, however, show that the rates we detected in the field are likely high enough to drive ecological change, such as reducing populations," she said.

Although the two species mate, they can't produce offspring. In fact, their mating makes the female yellow fever mosquito sterile. This means the Asian tiger mosquito is driving out the yellow fever mosquito in shared ecosystems.

But a female Asian tiger mosquito that mates with a male yellow fever mosquito can go on to mate with a male Asian tiger mosquito and produce offspring. That's because the proteins passed on by the male yellow fever mosquito do not trigger female rejection, Bargielowski said. On the other hand, a female yellow fever mosquito mated by a male Asian tiger mosquito cannot re-mate and produces no offspring.

What do these mating patterns mean? Bargielowski calls it an "asymmetrical" relationship, which can lead to the decline of mosquito populations. That happens when female mosquitoes lose the potential to re-mate, by mating with the wrong male, she said.

On the other hand, when yellow fever mosquitoes evolve to avoid this type of mating, they may be able to coexist with Asian tiger mosquitoes and repopulate areas from places where their populations are dwindling, Bargielowski said.

"We show that interspecific mating occurred at all sampled sites at levels high enough to be considered a probable driving force in the population dynamics of the two species," she said.

In most cases, this means the yellow fever mosquito population would go down, and the Asian tiger mosquito would increase.

"But the outcomes of this species interaction can be influenced by a number of factors, so the dynamics may change," Bargielowski said. If strong mating barriers are established, yellow fever mosquitoes may be able to recolonize areas from which they were displaced by Asian tiger mosquitoes, UF/IFAS scientists said.