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Non-quantitative adjustment of offspring sex ratios in pollinating fig wasps.

Wang RW, Sun BF, He JZ, Dunn DW - Sci Rep (2015)

Bottom Line: The foundresses tend to deposit their male eggs prior to female eggs.The observed increase in the proportion of male offspring as a function of foundress number results from density-dependent interference competition among the foundresses.The results here implied that genetic adjustment mechanisms of the sex ratio of fig wasps can only be triggered to be on or off and that the foundresses can not quantitatively adjust their sex ratio according to increased environmental selection pressure.

View Article: PubMed Central - PubMed

Affiliation: Center for Ecological and Environmental Sciences, Northwestern Polytechnical University, Xi'an, 710072, China.

ABSTRACT
Fig wasp is one of the most well known model systems in examining whether or not the parents could adjust their offspring sex ratio to maximize their gene frequency transmission in next generations. Our manipulative experiments showed that, in all of the five pollinator wasps of figs (Agaonidae) that have different averages of foundress numbers per syconium, almost the same proportions of male offspring are produced in the experiment that foundresses deposit one hour then are killed with ether (66.1%-70.1%) and over the lifespan of each foundress (14.0%-21.0%). The foundresses tend to deposit their male eggs prior to female eggs. The observed increase in the proportion of male offspring as a function of foundress number results from density-dependent interference competition among the foundresses. These results showed that the selection of gene frequency transmission through the behavioral adjustment in the evolution of sex ratio does not exist in these five fig wasps. The results here implied that genetic adjustment mechanisms of the sex ratio of fig wasps can only be triggered to be on or off and that the foundresses can not quantitatively adjust their sex ratio according to increased environmental selection pressure.

No MeSH data available.


Related in: MedlinePlus

Offspring number or sex ratio as a function of foundress number.(a) Total average numbers of egg deposited (measured as the number of galled flowers) vs foundress numbers and (b) the sex ratio vs foundress numbers in F. racemosa. Results indicate that total egg deposition will decrease after foundress numbers reach a threshold and the male offspring sex ratio will increase as a function of foundress number. The male offspring sex ratio does not asymptotically reach 50%, but increases to above the 50% level to 70% of which is the male offspring sex ratio in the first hour egg deposition. The sample size N ≥ 20 in each type of the experiments.
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f5: Offspring number or sex ratio as a function of foundress number.(a) Total average numbers of egg deposited (measured as the number of galled flowers) vs foundress numbers and (b) the sex ratio vs foundress numbers in F. racemosa. Results indicate that total egg deposition will decrease after foundress numbers reach a threshold and the male offspring sex ratio will increase as a function of foundress number. The male offspring sex ratio does not asymptotically reach 50%, but increases to above the 50% level to 70% of which is the male offspring sex ratio in the first hour egg deposition. The sample size N ≥ 20 in each type of the experiments.

Mentions: Interference competition among the foundresses results in decreases of female egg deposition. Sequence introduction can decrease the interference competition among the foundressses and the male offspring ratio in sequence introduction is lower than in simultaneous introduction, when the number of foundresses is high (Fig. 4). Including the syconium size as covariates, the sex ratio comparison results between sequence introduction and simultaneous introduction with 9 foundresses are: in F. racemosa, F1, 40 = 1.14, P > 0.05; in F. hispida, F1, 39 = 4.21, P < 0.05; in F. semicordata, F1, 39 = 4.68, P < 0.01; in F. benjamina (7 foundresses), F1, 39 = 46.98, P < 0.001. In F. racemosa, when the foundresses are manually increased due to simultaneous introduction, the male offspring ratio increases significantly as a function of the number of foundresses and can reach 70.1%. The male offspring proportion of the pollinators of F. racemsoa does not increase to an asymptote of 50% predicted in the Hamilton’s sex ratio evolution theory (see appendix). The averaged male offspring proportion with higher foundress number is significantly higher than in the treatments with lower foundress number (F9, 200 = 173.17, P < 0.001), (Fig. 5).


Non-quantitative adjustment of offspring sex ratios in pollinating fig wasps.

Wang RW, Sun BF, He JZ, Dunn DW - Sci Rep (2015)

Offspring number or sex ratio as a function of foundress number.(a) Total average numbers of egg deposited (measured as the number of galled flowers) vs foundress numbers and (b) the sex ratio vs foundress numbers in F. racemosa. Results indicate that total egg deposition will decrease after foundress numbers reach a threshold and the male offspring sex ratio will increase as a function of foundress number. The male offspring sex ratio does not asymptotically reach 50%, but increases to above the 50% level to 70% of which is the male offspring sex ratio in the first hour egg deposition. The sample size N ≥ 20 in each type of the experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4543974&req=5

f5: Offspring number or sex ratio as a function of foundress number.(a) Total average numbers of egg deposited (measured as the number of galled flowers) vs foundress numbers and (b) the sex ratio vs foundress numbers in F. racemosa. Results indicate that total egg deposition will decrease after foundress numbers reach a threshold and the male offspring sex ratio will increase as a function of foundress number. The male offspring sex ratio does not asymptotically reach 50%, but increases to above the 50% level to 70% of which is the male offspring sex ratio in the first hour egg deposition. The sample size N ≥ 20 in each type of the experiments.
Mentions: Interference competition among the foundresses results in decreases of female egg deposition. Sequence introduction can decrease the interference competition among the foundressses and the male offspring ratio in sequence introduction is lower than in simultaneous introduction, when the number of foundresses is high (Fig. 4). Including the syconium size as covariates, the sex ratio comparison results between sequence introduction and simultaneous introduction with 9 foundresses are: in F. racemosa, F1, 40 = 1.14, P > 0.05; in F. hispida, F1, 39 = 4.21, P < 0.05; in F. semicordata, F1, 39 = 4.68, P < 0.01; in F. benjamina (7 foundresses), F1, 39 = 46.98, P < 0.001. In F. racemosa, when the foundresses are manually increased due to simultaneous introduction, the male offspring ratio increases significantly as a function of the number of foundresses and can reach 70.1%. The male offspring proportion of the pollinators of F. racemsoa does not increase to an asymptote of 50% predicted in the Hamilton’s sex ratio evolution theory (see appendix). The averaged male offspring proportion with higher foundress number is significantly higher than in the treatments with lower foundress number (F9, 200 = 173.17, P < 0.001), (Fig. 5).

Bottom Line: The foundresses tend to deposit their male eggs prior to female eggs.The observed increase in the proportion of male offspring as a function of foundress number results from density-dependent interference competition among the foundresses.The results here implied that genetic adjustment mechanisms of the sex ratio of fig wasps can only be triggered to be on or off and that the foundresses can not quantitatively adjust their sex ratio according to increased environmental selection pressure.

View Article: PubMed Central - PubMed

Affiliation: Center for Ecological and Environmental Sciences, Northwestern Polytechnical University, Xi'an, 710072, China.

ABSTRACT
Fig wasp is one of the most well known model systems in examining whether or not the parents could adjust their offspring sex ratio to maximize their gene frequency transmission in next generations. Our manipulative experiments showed that, in all of the five pollinator wasps of figs (Agaonidae) that have different averages of foundress numbers per syconium, almost the same proportions of male offspring are produced in the experiment that foundresses deposit one hour then are killed with ether (66.1%-70.1%) and over the lifespan of each foundress (14.0%-21.0%). The foundresses tend to deposit their male eggs prior to female eggs. The observed increase in the proportion of male offspring as a function of foundress number results from density-dependent interference competition among the foundresses. These results showed that the selection of gene frequency transmission through the behavioral adjustment in the evolution of sex ratio does not exist in these five fig wasps. The results here implied that genetic adjustment mechanisms of the sex ratio of fig wasps can only be triggered to be on or off and that the foundresses can not quantitatively adjust their sex ratio according to increased environmental selection pressure.

No MeSH data available.


Related in: MedlinePlus