Precise sex allocation, local mate competition, and sex ratio shifts in the parasitoid wasp Trichogramma pretiosum

AbstractStudies on mating ecology and sex allocation in fig-parasitizing wasps ovipositing from outside the fig have given valuable insights into known factors that are responsible for the theory of sex ratio. Similarly, internally ovipositing fig-parasitizing wasps and fig-pollinating wasps provide interesting models for comparative analysis. In addition to the fig-pollinating wasp Eupristina sp., we found that Ficus curtipes hosts two species of internally ovipositing fig-parasitizing wasps: D. yangi and Lipothymus sp. Eupristina sp. males showed less aggression. Eupristina sp. has wingless males that mate only within the natal patch, providing excellent examples of full local-mate competition. D. yangi males showed high levels of aggression and lethal combat. D. yangi has winged males but mate mostly within the natal patch. Only a few matings occur after male dispersal. Its sex ratio was lower than the prediction of partial local mate competition theory. Wingless male Lipothymus sp., which mate partly after dispersal, did not present fatal fight. Therefore, the mating behaviour of D. yangi and Lipothymus sp. did not follow predicted patterns, based on wing morph. The mating pattern of D. yangi and Lipothymus sp. should follow the partial local mate competition theory. Furthermore, there was not a significant correlation between the proportion of males and the proportion of fruit parasitized in both winged D. yangi males and wingless Lipothymus sp. males.

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Solving the sex ratio scandal in Melittobia wasps

10.1101/2020.11.16.384768 ◽

2020 ◽

Author(s):

Jun Abe ◽

Ryosuke Iritani ◽

Koji Tsuchida ◽

Yoshitaka Kamimura ◽

Stuart A. West

Keyword(s):

Sex Ratio ◽

Sex Allocation ◽

Laboratory Experiments ◽

Sex Ratios ◽

Local Mate Competition ◽

Mate Competition ◽

Offspring Sex ◽

Local Mate ◽

Close Relatives

AbstractThe scandalous sex ratio behaviour of Melittobia wasps has long posed one of the greatest problems for the field of sex allocation. In contrast to the predictions of theory, and the behaviour of numerous other organisms, laboratory experiments have found that Melittobia females do not produce less female-biased offspring sex ratios when more females lay eggs on a patch. We resolve this scandal, by showing that, in nature, females of M. australica have sophisticated sex ratio behaviour, where their strategy also depends upon whether they have dispersed from the patch where they emerged. When females have not dispersed, they will be laying eggs with close relatives, which keeps local mate competition high, even with multiple females, and so they are selected to produce consistently female-biased sex ratios. Laboratory experiments mimic these conditions. In contrast, when females disperse, they will be interacting with non-relatives, and so they adjust their sex ratio depending upon the number of females laying eggs. Consequently, females appear to use dispersal status as an indirect cue of relatedness, and whether they should adjust their sex ratio in response to the number of females laying eggs on the patch.

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Sex ratio response to conspecifics in a parasitoid wasp: test of a prediction of local mate competition theory and alternative hypotheses

Behavioral Ecology and Sociobiology ◽

10.1007/s00265-002-0492-0 ◽

2002 ◽

Vol 52 (1) ◽

pp. 17-24 ◽

Cited By ~ 17

Author(s):

King B.

Keyword(s):

Sex Ratio ◽

Parasitoid Wasp ◽

Local Mate Competition ◽

Mate Competition ◽

Competition Theory ◽

Local Mate ◽

Alternative Hypotheses ◽

Ratio Response

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A solution to a sex ratio puzzle in Melittobia wasps

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2024656118 ◽

2021 ◽

Vol 118 (20) ◽

pp. e2024656118

Author(s):

Jun Abe ◽

Ryosuke Iritani ◽

Koji Tsuchida ◽

Yoshitaka Kamimura ◽

Stuart A. West

Keyword(s):

Sex Ratio ◽

Sex Allocation ◽

Laboratory Experiments ◽

Sex Ratios ◽

Local Mate Competition ◽

Mate Competition ◽

Offspring Sex ◽

Local Mate ◽

Close Relatives

The puzzling sex ratio behavior of Melittobia wasps has long posed one of the greatest questions in the field of sex allocation. Laboratory experiments have found that, in contrast to the predictions of theory and the behavior of numerous other organisms, Melittobia females do not produce fewer female-biased offspring sex ratios when more females lay eggs on a patch. We solve this puzzle by showing that, in nature, females of Melittobia australica have a sophisticated sex ratio behavior, in which their strategy also depends on whether they have dispersed from the patch where they emerged. When females have not dispersed, they lay eggs with close relatives, which keeps local mate competition high even with multiple females, and therefore, they are selected to produce consistently female-biased sex ratios. Laboratory experiments mimic these conditions. In contrast, when females disperse, they interact with nonrelatives, and thus adjust their sex ratio depending on the number of females laying eggs. Consequently, females appear to use dispersal status as an indirect cue of relatedness and whether they should adjust their sex ratio in response to the number of females laying eggs on the patch.

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Effects of constrained females on offspring sex ratios of Nasonia vitripennis in relation to local mate competition theory

Canadian Journal of Zoology ◽

10.1139/z05-006 ◽

2004 ◽

Vol 82 (12) ◽

pp. 1969-1974 ◽

Cited By ~ 8

Author(s):

B H King ◽

J A D'Souza

Keyword(s):

Sex Ratio ◽

Empirical Studies ◽

Virgin Female ◽

Parasitoid Wasp ◽

Local Mate Competition ◽

Mate Competition ◽

Nasonia Vitripennis ◽

Competition Theory ◽

Local Mate ◽

Mated Female

Empirical studies of how constrained females affect sex ratio are few. Constrained females are those that can produce only sons (e.g., in haplodiploid species, females that have not mated or older females that have used up their sperm). In the parasitoid wasp Nasonia vitripennis (Walker, 1836), failure to mate soon after emergence increased the probability of a female being constrained and thus affected sex ratio directly. Local mate competition theory shows that whether a female is constrained can also affect sex ratio indirectly by affecting what sex ratio other females produce. However, this was not the case in N. vitripennis. A female's sex ratio was not significantly different when she was with another young mated female versus a virgin female or an old mated female depleted of sperm. These results suggest that N. vitripennis females may be unable to recognize whether another female is constrained. The increased proportion of sons in response to other females relative to when alone did not persist the day after exposure.

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