A team of Carleton University researchers are making waves with their new findings about the nature of mimicry in hover flies.
They set out to find out why some hover flies have evolved to be almost indistinguishable from wasps, while others have evolved only a crude resemblance. Their findings were published in the latest issue of Nature, in an article called: “A comparative analysis of the evolution of imperfect mimicry.”
“Mimicry provides some of the most exquisite examples of the power of natural selection, but there are also some examples of rather poor mimicry and we wanted to know why natural selection appears to have gone only half of the way in these cases,” said Tom Sherratt, professor in the Department of Biology at Carleton University.
Hover flies, also known as flower flies, provide some of the best examples of imperfect mimicry. Within the range of hover fly species there are high fidelity mimics of stinging wasps and bees, while other species are so poor in resemblance one might wonder why natural predators are ever fooled. Sherratt and his former master’s student, Heather Penney, along with other Carleton researchers, set out to figure out why.
To conduct their work, they first had to quantify the similarity of a given species (the fly mimics) to others (the wasp or bee models), a process similar to comparing apples to oranges. They did this using both human rankings and statistical methods. Next, they had to figure out how all the species of hover flies in their data set were related to one another. They did this by examining their genetics in collaboration with Jeff Skevington from Agriculture and Agri-Food Canada. Once these ingredients were in place they could look for patterns and found that “bigger is better” when it comes to mimicry.
“It seems that large hover flies face more intense scrutiny from predators and therefore they need to look much closer to a wasp than the smaller, less substantial flies,” said Sherratt. “There is a famous saying that ‘Nothing makes sense in biology except in the light of evolution.’ It is just as important to investigate examples of seemingly poor adaptation than sitting back and enjoying the celebrated examples of adaptation we see in textbooks.”
Photo credit: Steve Marshall