Ito Emi, Yamada Yoshihiro Y
Insect Ecology Laboratory, Graduate School of Bioresources, Mie University, Tsu, Mie, Japan.
Insect Sci. 2014 Dec;21(6):741-9. doi: 10.1111/1744-7917.12054. Epub 2014 Feb 18.
Superparasitism in solitary parasitoids results in fatal competition between the immature parasitoids, and consequently only one individual can emerge. In the semisolitary ovicidal parasitoid Echthrodelphax fairchildii (Hymenoptera: Dryinidae), 2 adults can emerge under superparasitism with a short interval (<24 h) between the first and second ovipositions. We determined the female parasitoid's behavioral responses under self- and conspecific superparasitism bouts with first-to-second oviposition intervals of ≤2 h. The self- and conspecific superparasitizing frequencies increased up to an oviposition interval of 0.75 h, with the former remaining lower than the latter, particularly for oviposition intervals of ≤0.25 h, suggesting the existence of self-/conspecific discrimination. The superparasitizing frequency plateaued for oviposition intervals of ≥0.75 h, with no difference between self- and conspecific superparasitism. The ovicidal-probing frequency did not differ under self- and conspecific superparasitism, and was usually <20%. The females exhibited no preference for the oviposition side (i.e., ovipositing on the side with or without the first progeny) and almost always laid female eggs for any oviposition interval under self- and conspecific superparasitism. The sex ratio was not affected by the type of superparasitism, oviposition sides, or the occurrence of ovicidal probing. These observed results about the oviposition side, ovicidal probing, and sex ratios differed from the predictions obtained assuming that the females behave optimally. Possible reasons for the discrepancies are discussed: likely candidates include the high cost of selecting oviposition sides and ovicidal probing, and, for the sex ratio, the low frequency of encountering suitable hosts before superparasitism bouts.
孤雌寄生蜂中的过寄生会导致未成熟寄生蜂之间的致命竞争，因此通常只有一只个体能够羽化。在半孤雌杀卵寄生蜂费氏埃氏蚜小蜂（膜翅目：螯蜂科）中，若首次和第二次产卵间隔较短（<24小时），过寄生情况下会有2只成虫羽化。我们确定了雌蜂在首次与第二次产卵间隔≤2小时的自身过寄生和同种过寄生情况下的行为反应。自身过寄生和同种过寄生频率在产卵间隔达到0.75小时之前均有所增加，前者始终低于后者，尤其是在产卵间隔≤0.25小时时，这表明存在自身/同种识别。对于产卵间隔≥0.75小时，过寄生频率趋于平稳，自身过寄生和同种过寄生之间没有差异。杀卵探查频率在自身过寄生和同种过寄生情况下没有差异，通常<20%。雌蜂对产卵侧没有偏好（即在有或没有第一只后代的一侧产卵），并且在自身过寄生和同种过寄生的任何产卵间隔下几乎总是产雌卵。性别比例不受过寄生类型、产卵侧或杀卵探查发生情况的影响。这些关于产卵侧、杀卵探查和性别比例的观察结果与假设雌蜂行为最优时获得的预测结果不同。文中讨论了差异产生的可能原因：可能的因素包括选择产卵侧和杀卵探查的成本较高，以及对于性别比例而言，在过寄生事件之前遇到合适寄主的频率较低。
