Effects of time‐dependent competition for oviposition sites on clutch sizes and offspring sex ratios in a fig wasp

Abstract

T. 2002. Effects of time-dependent competition for oviposition sites on clutch sizes and offspring sex ratios in a fig wasp. -Oikos 96: 31 -35.

Effect of local mate competition on fig wasp sex ratios

“…We observed that each increase of one foundress produced broods seven to 13% larger than the previous one. If sequential oviposition takes place, as reported in the literature (Kinoshita et al, 2002;Moore et al, 2002), the second foundress probably contributes with a smaller proportion of eggs to the total brood. The weak adjustment between the number of foundresses and total brood size (R 2 = 0.1, Fig.…”

“…[603][604][605][606][607][608][609][610]2006 such a condition, first-arriving foundresses laid large female-biased clutches, contributing to more female-biased sex ratios. If P. tonduzi behaves like other fig wasp species [e.g., Liporrhopalum tentacularis (Moore et al, 2002) and Blastophaga nipponica (Kinoshita et al, 2002)], foundresses that arrive later will lay small less female-biased clutches, by facultatively adjusting their brood sex ratios according to the LMC level or by laying the males at the start of an oviposition bout (Kinoshita et Moore et al, 2002). The positive correlation between the P. tonduzi sex ratio and the brood size supports this hypothesis.…”

“…Thus, sex ratios vary from 1/2 (low level of inbreeding) or 1/3 (high level of inbreeding) for a high number of foundresses to zero for one foundress, although realistically enough males must be produced to ensure that all females are mated (Hamilton, 1967). Pollinating fig wasps have been considered as a model system to study LMC (Hamilton, 1979;Frank, 1985;Herre, 1985Herre, , 1987, although theoretical assumptions of knowledge of others ovipositing and of equal foundress contributions to broods may be violated (Kathuria et al, 1999;Kinoshita et al, 2002;Moore et al, 2002). In this paper, we analysed the effect of LMC (number of foundresses) on the sex ratio of the offspring of fig wasps, Pegoscapus tonduzi, which pollinates Ficus citrifolia in Brazil.…”

The mechanism of sex ratio adjustment in a pollinating fig wasp

“…These arguments receive support from B. nipponica: foundresses are less oviposition site limited in multifoundress figs than in L. tentacularis (Kinoshita et al 2002). The findings presented here, though, indicate another factor likely to affect cue use patterns.…”

“…Hence, to maintain the optimal sex ratio as clutch size increases, they should produce mostly male offspring at the start of oviposition bouts, followed by mostly females with a few males interspersed (see also Stubblefield & Seger 1990). However, clutch and brood sex ratios similar to those observed could also be as a consequence of another strategy, that of depositing a number of males at the beginning of oviposition bouts followed by only females (see also Herre et al 1997;Kinoshita et al 2002;Moore et al 2002;Kjellberg et al 2005). To determine whether foundresses use clutch size as a cue or pursue a 'males first' strategy, we quantify the sequence in which they deposit male and female offspring by using insecticide to terminate oviposition bouts at varying times after entry to the fig.…”