Evol Ecol Res 16: 605-616 (2015)     Full PDF if your library subscribes.

Sex ratio shifts of the solitary parasitoid wasp, Pachycrepoideus vindemmiae (Hymenoptera: Pteromalidae), to other foundresses

Qian Li, Lei Xie, Wei Chen, Xin Fang, Feng-Fei Zhang and Hao-Yuan Hu

Key Laboratory of Biotic Environment and Ecological Safety in Anhui Province, College of Life Sciences, Anhui Normal University, Wuhu, Anhui, China

Correspondence: H.-Y. Hu, College of Life Sciences, Anhui Normal University, Wuhu, Anhui 241000, China.
e-mail: haoyuanhu@126.com

ABSTRACT

Background: When parasitoid wasps oviposit in a limited patch, local mate competition (LMC) theories predict that, as foundress density rises, the sex ratio of offspring will be less biased towards females.

Hypothesis: Parasitoid wasp females in an experimental test should adjust their offspring sex ratio in response to the presence of other females.

Goal: Measure the sex ratio shifts of each foundress in the solitary parasitoid wasp, Pachycrepoideus vindemmiae.

Methods: Allow females to oviposit either alone or in a pair. Use an SSR-mark to determine which offspring belong to which female.

Results: When females oviposited alone, they produced fewer male offspring and a smaller proportion of males than when two females oviposited together. This result differed during the oviposition period. On the first day of oviposition, foundress number had no significant effect on offspring sex ratio. However, on the following days, the proportion of male offspring from two foundresses was significantly higher than that from one foundress.

Conclusion: The response of offspring sex ratio to foundress number in P. vindemmiae is in line theoretically with local mate competition theories.

Keywords: behaviour, Pachycrepoideus vindemmiae, solitary parasitoid wasp, sex ratio, local mate competition.

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