松褐天牛肿腿蜂的产卵模式:雄性先产的有利原则

Oviposition Pattern of Sclerodermus alternatusi:Benefits of Laying Unfertilized Eggs First

本研究分别设计了去除松褐天牛肿腿蜂Sclerodermus alternatusi母蜂第1 d所产的卵(处理1)和在松褐天牛肿腿蜂产卵1 d后去除母蜂(处理2),并统计其子代性别构成和比例这2组数据来明确其产卵行为特征,进而来验证松褐天牛肿腿蜂在一次产卵行为中是否会优先产出未受精的卵。研究发现,在处理2中仅保留了肿腿蜂第1 d所产的卵后,24例有效重复中仅有1例无雄性后代;对照组(接蜂后无处理)中所有重复均有雄性后代。然而,在处理1去除了肿腿蜂第1 d所产的卵后,25例有效重复中子代无雄蜂的样本数达到了10例,其雄蜂缺失的比例显著高于处理2和对照组。处理1和处理2均羽化出26头雄蜂,其平均单雌产雄量分别为1.04和1.08头,显著低于对照组的1.98头。以上研究结果表明,松褐天牛肿腿蜂的群体构成是显著的偏雌性,母蜂一次产卵行为中会在最初的时间内将雄性后代产出,而随后再陆续地产出雌性后代。这种雄性后代先产的行为特征对肿腿蜂控制其较高的子代雌性比和子代雌蜂在羽化后可第一时间完成交配是有利的。

To understand whether the bethylid parasitic wasp,Sclerodermus alternatusi Yang,adjusts the sex ratio of their offspring by laying the unfertilized eggs first,the oviposition traits of this parasitoid were investigated in the laboratory.Three treatments of the parasitoid eggs,including removal of the eggs laid in the first day(T1),reserve of the eggs laid in the first day only(T2),and reserve of all the eggs laid in all days(CK),were established for the analysis.It was found that only one out of 24 samples did not have male offspring in T2,while all of the samples in CK had male offspring.In contrast,in T1,there were male offspring in 15 out of 25 samples,which was significantly higher than those in T2 and CK.There were a total of 26 males emerged from T1 or T2.The mean numbers of male offspring per mother wasp in T1(1.04)and T2(1.08)were significantly lower than that in the CK(1.98).The results indicate that extremely female-biased sex ratio is a general phenomenon in this bethylid wasp,and the unfertilized eggs are preferentially laid first by the mother wasps.Laying unfertilized eggs first can guarantee the female-biased sex ratio of offspring in one clutch and contribute to the efficient and abundant mating for females.