Data from: Effects of inbreeding on a gregarious parasitoid wasp with complementary sex determination

Inbreeding and inbreeding depression are processes in small populations of particular interest for a range of human activities such as animal breeding, species conservation or pest management. In particular, biological control programs should benefit from a thorough understanding of the causes and consequences of inbreeding because natural enemies experience repetitive bottlenecks during importation, laboratory rearing, and introduction. Predicting the effect of inbreeding in Hymenopteran parasitoid wasps, frequently used in biological control programs, is nonetheless a difficult endeavor. In haplodiploid parasitoids, the purge of deleterious alleles via haploid males should reduce genetic load, but if these species also have complementary sex determination (CSD) abnormal diploid males will be produced, which may jeopardize the success of biological control introductions. <i>Mastrus ridens</i> is such a parasitoid wasp with CSD, introduced to control the codling moth, <i>Cydia pomonella</i> (L.). We studied its life history traits in the laboratory under two conditions: inbred (full sib) and outbred (non-sib) crosses, across five generations, in order to examine the consequences of inbreeding in this species. We found that in inbred lines non reproducing females live less, the number of daughters produced was lower, and that sex ratio (proportion of males) and proportion of diploid males were higher. Diploid males were able to produce fertile daughters, but fewer than haploid males. Lineage survival was similar for inbred and outbred lines across the five generations. The most significant decrease in fitness was thus a consequence of the production of diploid males, but this effect was not as extreme as in most other species with CSD, due to the fertility of diploid males. This study highlights the importance of determining the type of sex determination in parasitoid wasps used for biological control, and the importance of maintaining genetic diversity in species with CSD when importation or augmentation is the goal.近交（inbreeding）与近交衰退（inbreeding depression）是小种群中的核心生态与进化过程，在动物育种、物种保护及害虫治理等诸多人类活动领域中备受关注。具体而言，生物防治项目亟需深入解析近交的成因与后果，因为天敌在引种、实验室饲养及野外释放过程中会经历反复的种群瓶颈效应。不过，预测膜翅目寄生蜂（Hymenopteran parasitoid wasps）的近交效应颇具挑战——这类寄生蜂常被应用于生物防治项目。对于单倍二倍体寄生蜂（haplodiploid parasitoids）而言，通过单倍体雄蜂清除有害等位基因（deleterious alleles）可降低遗传负荷（genetic load），但倘若这类物种同时存在互补性决定（complementary sex determination, CSD）机制，则会产生异常二倍体雄蜂，进而可能危及生物防治项目的实施成效。*Mastrus ridens* 便是一类具备CSD机制的寄生蜂，被引入用以防治苹果蠹蛾（*Cydia pomonella* (L.)）。本研究在实验室条件下设置全同胞近交与非同胞远交两组杂交处理，历经五代实验，对该物种的生活史性状（life history traits）展开观测，以探究近交对其产生的影响。研究结果显示，近交品系中的不产卵雌蜂寿命更短，子代雌蜂数量更少，且性比（sex ratio，雄虫占比）与二倍体雄蜂比例均更高。二倍体雄蜂虽可产生可育雌性后代，但其子代数量少于单倍体雄蜂。历经五代实验后，近交品系与远交品系的家系存活率并无显著差异。因此，种群适合度（fitness）的显著下降主要源于二倍体雄蜂的产生，但由于二倍体雄蜂具备育性，该效应并未像多数其他具备CSD机制的物种那般剧烈。本研究凸显了明确生物防治所用寄生蜂的性别决定类型的重要性，同时也表明，当以天敌引种或增殖释放（augmentation）为目标时，维持具备CSD机制物种的遗传多样性至关重要。