NYSCF – Robertson Investigator Uncovers Evolutionary Secrets Behind Fruit Fly Mate Selection

A bunch of fruit flies gather around an overripe fruit. It’s the fruit fly version of a bar on a Saturday night, and these flies see a potential for mating. A male taps his foreleg onto a female’s abdomen to “taste” her pheromones, after which a signal is sent to the part of his brain that regulates courtship. But there are many types of flies gathered around this fruit, and somewhere in this process, the male fly has to discern whether or not his potential mate is a member of his species. If she is, he continues to court. If she isn’t, he stops.

A new study in Nature from NYSCF – Robertson Investigator and The Rockefeller University Gabrielle H. Reem and Herbert J. Kayden Associate Professor of Biochemistry, Biophysics, Chemical Biology, and Structural Biology Vanessa Ruta, PhD, examined how flies keep from mating with those outside their species. The results offer insight into how evolution has influenced a system for choosing the correct mate.

Dr. Ruta and her team used genetic and imaging tools to track the electrochemical impulses that occur in male fruit flies of two different species (D. melanogaster flies and D. simulans flies) as they choose a mate. Female D. melanogaster flies and D. simulans flies produce different pheromones, and while these pheromones encourage male flies of the same species as the female to mate, they have the opposite effect in males of different species. Scientists have long assumed that this is due to evolutionary changes in the peripheral nervous system of the flies (which houses the organs that detect and process pheromones), but Dr. Ruta’s team wanted to determine if this is truly where the species of flies diverge.

What the team found was that both species of male flies perceived the pheromones of a female the same way regardless of whether she was in his species or not. The difference between what makes one pheromone attractive to one fly and repulsive to another occurs deep in the fly’s brain in a group of neurons that control mating behavior. When the fly detects a pheromone from a female of his own species, a group of excitatory neurons activate the neurons that control mating behavior. When a fly detects a pheromone from a female of a different species, inhibitory neurons activate instead, shutting down the mating behavior neurons. This showed that contrary to previous beliefs, the evolutionary changes in each fly took place in the central nervous system, not the peripheral nervous system.

Dr. Ruta and her team next plan to study more species of flies to pinpoint additional differences in how evolutionary changes drive behavior.

For more information on this study, check out this article from The Rockefeller University.