Queen-worker conflicts over male production and sex allocation in a primitively eusocial wasp.
In a colony headed by a single monandrous foundress, theories predict that conflicts between a queen and her workers over both sex ratio and male production should be intense. If production of males by workers is a function of colony size, this should affect sex ratios, but few studies have examined how queens and workers resolve both conflicts simultaneously. We conducted field and laboratory studies to test whether sex-ratio variation can be explained by conflict over male production between queen and workers in the primitively eusocial wasp Polistes chinensis antennalis. Worker oviposition rate increased more rapidly with colony size than did queen oviposition. Allozyme and microsatellite markers revealed that the mean frequency of workers' sons among male adults in queen-right colonies was 0.39 +/- 0.08 SE (n = 22). Genetic relatedness among female nestmates was high (0.654-0.796), showing that colonies usually had a single, monandrous queen. The mean sex allocation ratio (male investment/male and gyne investments) of 46 queen-right colonies was 0.47 +/- 0.02, and for 25 orphaned colonies was 0.86 +/- 0.04. The observed sex allocation ratio was likely to be under queen control. For queen-right colonies, the larger colonies invested more in males and produced reproductives protandrously and/or simultaneously, whereas the smaller colonies invested more in females and produced reproductives protogynously. Instead of positive relationships between colony size and worker oviposition rate, the frequency of workers' sons within queen-right colonies did not increase with colony size. These results suggest that queens control colony investment, even though they allow worker oviposition in queen-right colonies. Eggs laid by workers may be policed by the queen and/or fellow workers. Worker oviposition did not influence the outcome of sex allocation ratio as a straightforward function of colony size.
Tsuchida
Koji
K
Laboratory of Entomology, Faculty of Agriculture, Gifu University, Yanagido 1-1, Gifu 501-1193, Japan. tsuchida@cc.gifu-u.ac.jp
Saigo
Takaharu
T
Nagata
Norio
N
Tsujita
Sumiko
S
Takeuchi
Kazuki
K
Miyano
Shinya
S
D000483:Alleles; D000818:Animals; D005075:Biological Evolution; D004586:Electrophoresis; D005247:Feeding Behavior; D005260:Female; D008297:Male; D018895:Microsatellite Repeats; D008954:Models, Biological; D011156:Population Density; D012098:Reproduction / Q000502:physiology; D012744:Sex Ratio; D012726:Sexual Behavior, Animal / Q000502:physiology*; D014863:Wasps / Q000502:physiology*