COORDINATION OF THE SEXUAL SIGNALING SYSTEM AND THE GENETIC-BASIS OF DIFFERENTIATION BETWEEN POPULATIONS IN THE BROWN PLANTHOPPER, NILAPARVATA-LUGENS

Substrate-transmitted sexual signals and female responses to synthetic male signals were analysed for three populations of brown planthopper , Nilaparvata lugens (Homoptera: Delphacidae). Mean female preferences closely match mean male signal pulse repetition frequencies (PRF) in each population, despite marked differences among populations in PRF o f both male and female signals. Female response windows (the range of male signal PRFs that elicit responses) were similar in all population s and wide relative to male signal variation. Tile Wright-Castle-Lande method was used to estimate the number of loci affecting differences between populations in male and female sexual signals and female prefe rences. Estimates obtained using the Lande formulae were compared with estimates from an iterative model-fitting approach. No sex linkage wa s observed. The characters conformed to the expectations of additive i nheritance, with directional dominance in two cases. Estimates for the number of loci involved in signal characters were low, ranging from 1 .4 to 5.3. After corrections for bias in the estimation method, estima tes range from 2 to 16 but are still substantially lower than the reco mbination index of about 25. Estimates of the number of loci influenci ng female preference were unreliable. The two estimation methods gave compatible results but the iterative estimation method made better use of the data and gave clearer guidance on the support for the estimate s. The results are discussed in the light of potential causes of diver gence in sexual signalling systems.