Erik van Bergen, at the University of Cambridge, reported a unique experiment that determined how female butterflies avoid breeding with inbred male butterflies in the March 5, 2013, issue of the journal Proceedings of the Royal Society B.
Inbreeding produces the potential for a reduced gene pool, higher levels of genetic disorders, and an overall reduction in species viability over time. Only a few of the variety of natural means of inbreeding avoidance have been scientifically documented.
The study of the butterfly species Bicyclus anynana is particularly important for species survival because 50 percent of inbred males are sterile.
The researchers purposefully bred a group of inbred males. The genitals of the inbred males and outbred males were coated with different colored fluorescent dyes to track which group were more attractive to a group of female butterflies that included the sisters of the inbred male group. Deposits of the dyes on the female were indicative of attraction.
Some of the female butterflies had their antennae covered with nail polish to prevent female reception of sex pheromone produced by males.
The researchers found that female butterflies of this species preferentially mated with outbred males if the females were able to detect the male sex pheromone. Inbred males produced a lower level of the sex pheromone and were less likely to be selected as mates by the female butterflies.
The phenomenon is assumed to be species independent and common across all species of butterflies.