Paternity and female remating in Requena verticalis (Orthoptera: Tettigoniidae)

A study of sperm competition in the tettigoniid Requena verticalis showed a pattern that differs from the sperm mixing noted in most insects (Parker, 1970; Gwynne, 1984). The paternity for the first of two male R.verticalis to mate was virtually complete (Gwynne, 1988a). The lack of paternity of the second males was of particular interest because the study used radiolabelling and genetic markers to show that these males provided a material investment in the first male’s offspring. The investment is a large spermatophylax, a part of the spermatophore eaten by the female, and enhances the fitness of her offspring (Gwynne, 1988b). The question arises as to why second males mate, especially when spermatophyalx nutrients are costly to male R.verticalis (Davies & Dadour, 1989). Perhaps the 4-5-day female refractory period (Gwynne, 1986) used as the remating interval in Gwynne (1988a) does not reflect the actual remating interval in nature. Recent studies of R. verticalis support this contention. First, the fact that virgins outcompete already-mated females in the struggle for mates (Lynam et al., 1992) and are probably preferred by males (Simmons etal . , 1994) provides a mechanism for delayed female remating. Second, there is direct field evidence of such a delay: Simmons et al. (1994) showed a 13-day interval between two very distinct modes of adult ages of thirty-nine female observed mating; and, by monitoring a population of marked females for 15 days, K.-G. Heller (unpublished) noted an 11-day and a 13-day remating interval in the two rematings he observed during the study period. Evidence that female remating interval can influence paternity in orthopterans was found in Locusta migratoria (Acrididae). If female remating is delayed until after oviposition, paternity of the second male to mate (P2) more than doubles (Parker & Smith, 1975). Here we examine the relative paternity of two R.verticalk males when remating is delayed until after oviposition.