Understanding the evolution of mosquito host preference

"I get bitten by mosquitoes all the time, but my friend never seems bothered by them!"

Perhaps you've noticed that some people seem much more attractive to mosquitoes than others are (perhaps you're that unfortunate person in your friend group!). Hungry mosquitoes discriminate not only among different humans, but can also exhibit striking preferences for certain host species. Some mosquito species (or subspecies) have a particular liking for human blood-meals.1,2 Unsurprisingly, these human-preferring mosquitoes are the primary vectors for devastating diseases like malaria, dengue, and yellow fever.

I'm studying how this preference has evolved in the yellow fever mosquito Aedes aegypti—how have less-choosy ancestral mosquitoes given rise to mosquitoes that specialize on biting humans? To understand the evolution of this choosiness, we need to understand the buffet of options mosquitoes are choosing from. Because mosquitoes rely on their sense of smell to choose a host3, the relevant sensory environment is the "odour space"—what do different animals smell like?

To answer this question, I'm collecting hair, fur, feather, and wool samples from many different animal species and extracting odour from them. Analysing these samples will yield an odour profile for each animal—a unique blend of chemical compounds in certain ratios that mosquitoes can use to discriminate among potential hosts. Using these odour profiles as input to a computational model, I hope to understand what evolutionary changes in mosquitoes' sense of smell underlie this change in their host preference—and what it is about human odour that makes our smell the most enticing option in the buffet.

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1. Pates HV, Takken W, Stuke K, Curtis CF (2001) Differential behaviour of Anopheles gambiae sensu stricto (Diptera: Culicidae) to human and cow odours in the laboratory. Bulletin of Entomological Research 91:289–296. doi: 10.1079/BER200198

2. McBride CS, Baier F, Omondi AB, et al (2014) Evolution of mosquito preference for humans linked to an odorant receptor. Nature 515:222–227. doi: 10.1038/nature13964

3. DeGennaro M, McBride CS, Seeholzer L, et al (2013) orco mutant mosquitoes lose strong preference for humans and are not repelled by volatile DEET. Nature 498:487–491. doi: 10.1038/nature12206