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.

在雌性储存精子的物种中，雄性可通过将精子策略性地安置于雌性的精子储存器官内，来干预父权分配。精子可在储存器官中发生混合或分层排布，这会打破“公平抽奖”式的随机分配模式，进而影响精子的使用规律。在部分昆虫类群中，不同交配产生的精子会被包装为离散的精包（spermatodoses），此类精包可在雌性的受精囊（spermatheca）中维持结构完整性，但目前学界对野生种群在自然交配条件下，精包如何调控精子使用模式的认知仍较为有限。本研究以在未经过人工操控的野外自然交配条件下完成交配的深色灌木螽斯（Pholidoptera griseoaptera）雌性个体为研究对象，探究了受精囊内精包的大小、相对位置以及竞争射精的数量对父权分配的影响。研究采集了交配季末期的雌性个体，并利用7个高多态性微卫星位点对实验室产出的卵进行父权归属鉴定。结果显示，雌性个体携带的精包数量中位数为3（范围1~6），36只受试雌性中仅6只同时携带2个及以上基因型一致的精包。分析表明，受精囊内精包的大小与相对位置均对父权分配存在显著影响：体型较小的精包，以及距离受精囊单一进出口较远的精包，其对应的雄性父权成功率会受到偏倚。此外，参与竞争的射精数量越多，单只雄性成功繁衍后代的概率越低。综上，精包大小与受精囊内的相对位置均会显著影响雄性的父权成功率。