Variation in courtship signals and hybridization between geographically definable populations of the rice Brown planthopper, Nilaparvata lugens (Stål)

Abstract

Variation in courtship signals and hybridization between geographically definable populations of the rice Brown planthopper, Nilaparvata lugens (Stal)Populations of Nzlaparvata lugens from 18 geographically defined and widely distributed regions in Asia and Australasia were maintained in the laboratory on growing rice plants. Crosses between some of these showed varying degrees of success in hybridization. Those between insects from Australia and the Solomon Islands had the lowest success rates, but in successful individual crosses there was little evidence of hybrid inviability. Behavioural barriers in the form of substrate transmitted courtship signals appeared to be primarily responsible for low success in hybridization. Pulse repetition frequenries of male calls were distinctive for different populations: those from Australia and the Solomon Islands showed the greatest difference. Divergence in mate recognition signals (pre-mating ethological isolating mechanisms) has apparently evolved in advance of general genetic incompatibilities (post-mating isolating mechanisms) in this species.

Co-ordination of the sexual signalling system and the genetic basis of differentiation between populations in the brown planthopper, Nilaparvata lugens

“…Both the JL and AR populations differed significantly (P<0.01) from the BR population for male and female signal PRFs, as expected from previous observations (Claridge et a!., 1985a(Claridge et a!., , 1988 (Table 1). …”

“…Despite the smaller sample sizes, this pattern is repeated for female preference measurements in the AR population. The BR preference results are closely similar to those of Butlin (1993) Previous studies of F1 hybrids (Claridge et aL, 1985a(Claridge et aL, , 1988 Survival of F2 individuals was high in BR-AR crosses, averaging 67 per cent. In BR-JL crosses, survival of the F2 on TN1 averaged 79 per cent but no individuals survived on Leersia hexandra out of nine replicates of 30 nymphs each.…”

“…This suggests that allelic substitutions between BR and JL have smaller effects on male PRF than substitutions between AR and BR, or substitutions influencing female PRF. It is very unlikely that the same loci influence both the male and female characters as there is no correlation among populations between male and female PRF either here or in other populations (Claridge et at., 1985a(Claridge et at., , 1988.…”

“…Therefore, when using the Lande (1981) (Lande, 1981). Neither the data available here (Table 1) nor previous analyses of hybrids (Claridge et al, 1985a(Claridge et al, , 1988 This procedure was implemented using the FTTNONUNEAR procedure of GENSTAT 5 (GENSTAT, 1987) which uses a modified Newton algorithm to search the parameter space, with explicit calculation of log-likelihoods. Starting parameter values were the observed means and variances, and variance estimates were constrained to be positive.…”

“…Bar is 2 s in each case. (Claridge et at., 1985a(Claridge et at., ,b, 1988. There is good evidence that the PRF of male song is important in female mate choice (Claridge et at., 1984).…”