THE GENETIC-CONTROL OF PHEROMONE PRODUCTION AND RESPONSE IN THE PINE ENGRAVER BEETLE IPS PINI

An understanding of the genetic coordination of signal and response in communication systems is an elusive quest in many organisms. Two hypo theses currently exist to explain the mechanism of coordination and it s evolution: (1) signal-response systems are a result of pleiotropic e ffects of a gene or genes controlling the neural network underlying bo th or, (2) independent genes produce the signal and response and selec tion acts similarly on the traits. In this study, we tested the hypoth esis that independently asserting genes control. the production of, an d 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' ma ting. If production and response are a result of pleiotropy then there should be no breakdown in the genetic correlation of the two traits u nder the 'no choice' mating. Both pheromone production by males and th e response to it by males and females are highly heritable, Male respo nse appears to be genetically unlinked to pheromone production; theref ore it is likely that the traits are not a result of pleiotropy. Inste ad, assortative mating may maintain the phenotypic correlation between the pheromone blend produced and the blend to which that individual r esponds.