Data from: Paternity analysis of wild caught females shows that sperm package size and placement influence fertilisation success in the bushcricket Pholidoptera griseoaptera

In species where females store sperm, males may try to influence paternity by the strategic placement of sperm within the female’s sperm storage organ. Sperm may be mixed or layered in storage organs and this can influence sperm use beyond a ‘fair raffle’. In some insects, sperm from different matings is packaged into discrete packets (spermatodoses), which retain their integrity in the female’s sperm storage organ (spermatheca), but little is known about how these may influence patterns of sperm use under natural mating conditions in wild populations. We examined the effect of the size and position of spermatodoses within the spermatheca and number of competing ejaculates on sperm use in female dark bushcrickets (Pholidoptera griseoaptera) that had mated under unmanipulated field conditions. Females were collected near the end of the mating season and seven hypervariable microsatellite loci were used to assign paternity of eggs laid in the laboratory. Females contained a median of 3 spermatodoses (range 1-6) and only 6 of the 36 females contained more than one spermatodose of the same genotype. Both the size and relative placement of the spermatodoses within the spermatheca had a significant effect on paternity, with a bias against smaller spermatodoses and those further from the single entrance/exit of the spermatheca. A higher number of competing males reduced the chances of siring offspring for each male. Hence both spermatodose size and relative placement in the spermatheca influence paternity success.在雌性具有精子储存能力的物种中，雄性可通过在雌性精子储存器官内精准排布精子来影响父权分配。精子可在储存器官内发生混合或分层排布，这会使精子的使用模式偏离“公平抽奖”机制。在部分昆虫中，不同交配事件产生的精子会被包装为独立的精子包囊（spermatodoses），这些包囊可在雌性的受精囊（spermatheca，即精子储存器官）中保持结构完整，但目前学界对野生种群自然交配条件下，此类包囊如何影响精子使用模式仍知之甚少。本研究以灰翅丛螽（dark bushcrickets，Pholidoptera griseoaptera）为研究对象，该物种的雌性个体均在未受人为干扰的野外条件下完成交配，我们借此考察了受精囊内精子包囊的大小、位置以及竞争射精次数对其精子使用模式的影响。研究样本于交配季末期采集获得，我们利用7个高变微卫星位点（hypervariable microsatellite loci）对实验室条件下产出的卵进行父权鉴定。雌性个体携带的精子包囊数量中位数为3（范围1~6），36只采样雌性中仅6只携带多个基因型一致的精子包囊。精子包囊的大小及其在受精囊内的相对位置均对父权分配产生显著影响：体积较小以及距离受精囊唯一出入口较远的精子包囊，其父权成功率显著偏低。参与交配竞争的雄性个体数量越多，单只雄性成功繁育子代的概率越低。综上，精子包囊的大小及其在受精囊内的相对位置，均会对雄性的父权成功率产生影响。