THE GENETIC-BASIS AND EVOLUTION OF ACOUSTIC MATE RECOGNITION SIGNALS IN A RIBAUTODELPHAX PLANTHOPPER (HOMOPTERA, DELPHACIDAE) .1. THE FEMALE CALL

Both sexes of the planthopper Ribautodelphax imitans produce species specific acoustic signals. Earlier experiments have shown that isolation between Ribautodelphax species in captivity is at least partly due to male preference for calls of conspecific females. The genetic basis of the female call is studied by bi-directional artificial selection for large and small interpulse intervals (IPI). This resulted in non-overlapping distributions of IPI after only five generations. The mean of eight realized heritability estimates over five generations was above 80%; estimates over ten generations were generally well above 50%. The character is shown to be of a polygenic nature, determined by at least 6 segregating genetic factors. The other features of the female call, strophe duration, and modulation of pulse repetition frequency within the strophe, showed significantly correlated responses. Sexual isolation tests after 10 generations of selection revealed significant symmetrical assortative mating, but coselected males did not exhibit a significant preference for playback calls of females from their own selection line. In view of the high heritability for the call character, and the considerable ecological isolation among Ribautodelphax species, it seems unlikely that the female call differentiated as an adaptation to prevent hybridization (reinforcement). More likely, call and call preference were shaped by sexual selection during allopatry, and may have (had) incidentally an effect in species isolation.