One quantitative trait locus for intra‐ and interspecific variation in a sex pheromone

Abstract

Even though premating isolation is hypothesized to be a major driving force in speciation, its genetic basis is poorly known. In the noctuid moth Heliothis subflexa, one group of sex pheromone components, the acetates, emitted by the female, plays a crucial isolating role in preventing interspecific matings to males of the closely related Heliothis virescens , in which females do not produce acetates and males are repelled by them. We previously found intraspecific variation in acetates in H. subflexa : females in eastern N orth A merica contain significantly more acetates than females in W estern M exico. Here we describe the persistence of this intraspecific variation in laboratory‐reared strains and the identification of one major quantitative trait locus ( QTL ), explaining 40% of the variance in acetate amounts. We homologized this intraspecific QTL to our previously identified interspecific QTL using restriction‐associated DNA ( RAD ) tags. We found that a major intraspecific QTL overlaps with one of the two major interspecific QTL . To identify candidate genes underlying the acetate variation, we investigated a number of gene families with known or suspected acetyl‐ or acyltransferase activity. The most likely candidate genes did not map to our QTL , so that we currently hypothesize that a transcription factor underlies this QTL . Finding a single, large QTL that impacts variation in pheromone blends between and within species is, to our knowledge, the first such example for traits that have been demonstrated to affect premating isolation.

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