Genetic analysis and population survey of sex pheromone variation in the adzuki bean borer moth, Ostrinia scapulalis

Abstract

Sexual communication in many moths occurs between females emitting a sex pheromone and males responding to it. Females of Ostrinia scapulalis (Lepidoptera: Crambidae) show a large variation in blend ratios of the two sex pheromone components (E)- and (Z)-11-tetradecenyl acetates. E type females produce a pheromone with a high percentage of (E)-11-tetradecenyl acetate, whereas Z type females produce the opposite blend. We established laboratory cultures of E and Z types. Females of the F₁ generation produced an intermediate blend (I type) in both reciprocal crosses of the E and Z cultures. Results of further crossing experiments suggested that the three pheromone types are primarily controlled by a single autosomal locus with two alleles. Also, analyses of the variation in pheromone blend within F₁, backcross and F₂ families suggested that other genetic factors modify the pheromone blend of the I and Z types. Investigation of the pheromone variation in natural populations at 14 localities in Japan has shown that the E type was predominant in northern Japan, whereas the pheromone was highly polymorphic in central Japan. At a locality in central Japan, the pheromone was constantly polymorphic for several years, and the pheromone type frequencies did not deviate from Hardy–Weinberg expectations, providing no evidence of selection or assortative mating between the pheromone types. Analyses of pheromone variation within families derived from feral females indicated that matings between a pair with different genotypes for pheromone production was occurring in natural populations. Overall, this study showed that the genetic basis of the pheromone variation in O. scapulalis is very similar to that in its sibling species Ostrinia nubilalis although the state of pheromone polymorphisms in natural populations appears to differ between the two species.

assortative mating, genetic variation, geographical variation, Lepidoptera, major gene, Ostrinia nubilalis, sex pheromone communication, within-population polymorphism