The genetic control of pheromone production and response in the pine engraver beetle Ips pini

Abstract

An understanding of the genetic coordination of signal and response in communication systems is an elusive quest in many organisms. Two hypotheses currently exist to explain the mechanism of coordination and its evolution: (1) signal-response systems are a result of pleiotropic effects of a gene or genes controlling the neural network underlying both or, (2) independent genes produce the signal and response and selection acts similarly on the traits. In this study, we tested the hypothesis that independently assorting genes control the production of, and response to, a sex pheromone in the pine engraver beetle, Ips pini. We measured the genetic correlation of production and response in sons from two situations: wild-caught pairs where there was some level of assortative mating and after five generations of forced ‘no choice’ mating. If production and response are a result of pleiotropy then there should be no breakdown in the genetic correlation of the two traits under the ‘no choice’ mating. Both pheromone production by males and the response to it by males and females are highly heritable. Male response appears to be genetically unlinked to pheromone production; therefore it is likely that the traits are not a result of pleiotropy. Instead, assortative mating may maintain the phenotypic correlation between the pheromone blend produced and the blend to which that individual responds.