Data from: Paternity analysis of wild-caught females shows that sperm package size and placement influence fertilization 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 three spermatodoses (range 1–6), and only six 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.

在雌性具备精子储存能力的物种中，雄性可通过将精子战略性地安置于雌性的精子储存器官（sperm storage organ）内，以影响自身的父权分配比例。精子可在储存器官中发生混合或分层排布，这会使精子的使用模式偏离经典的“公平抽奖”（fair raffle）模型。在部分昆虫类群中，不同交配事件产生的精子会被包装为离散的精子包囊（spermatodoses），这些包囊可在雌性的受精囊（spermatheca）中保持结构完整性，但目前针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的研究仍较为匮乏。本研究以未经过人工操控的野外交配条件下的雌性暗灌丛螽（Pholidoptera griseoaptera）为研究对象，探究了受精囊内精子包囊的大小、相对位置以及参与竞争的射精数量对精子使用模式的影响。研究样本为交配季末期采集的雌性个体，通过7个高变微卫星位点（microsatellite loci）对实验室条件下产出的卵进行父权鉴定。结果显示：雌性个体携带的精子包囊数量中位数为3（范围1~6），36只受试雌性中仅有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，具体表现为体型较小的包囊以及距离受精囊单一出入口较远的包囊会受到父权偏倚的排斥；参与竞争的雄性数量越多，单只雄性成功获得父权的概率越低。综上，精子包囊的大小及其在受精囊内的相对位置，均会显著影响雄性的父权成功率。