University of Lethbridge, 4401 University Drive West, Lethbridge, AB, T1K 3M4, Canada.
Queen's University, 116 Barrie Street, Kingston, ON, K7L 3N6, Canada.
Sci Rep. 2023 Mar 2;13(1):3528. doi: 10.1038/s41598-023-30441-1.
Parasitoids are small insects, (e.g., small wasps or flies) that reproduce by laying eggs on or within host arthropods. Parasitoids make up a large proportion of the world's biodiversity and are popular agents of biological control. Idiobiont parasitoids paralyze their hosts upon attack and thus are expected to only target hosts large enough to support offspring development. Host resources generally impact host attributes and life histories including size, development, and life span. Some argue slow host development in response to resource quality increases parasitoid efficacy (i.e., a parasitoid's ability to successfully reproduce on or within a host) due to longer host exposure to parasitoids. However, this hypothesis is not always supported and does not consider variation in other host traits in response to resources that may be important for parasitoids (e.g., variation in host size is known to impact parasitoid efficacy). In this study we test whether trait variation within host developmental stages in response to host resources is more important for parasitoid efficacy and life histories than trait variation across host developmental stages. We exposed seed beetle hosts raised on a food quality gradient to mated female parasitoids and measured the number of hosts parasitized and parasitoid life history traits at the scale of host stage- and age-structure. Our results suggest host food quality does not cascade to impact idiobiont parasitoid life histories despite large food quality effects on host life history. Instead, variation in host life histories across host developmental stages better predicts parasitoid efficacy and life histories, suggesting finding a host in a specific instar is more important for idiobiont parasitoids than finding hosts on or within higher quality resources.
寄生蜂是一类小型昆虫（例如，小蜂或蝇类），它们通过在宿主节肢动物的体表或体内产卵来繁殖。寄生蜂在世界生物多样性中占有很大比例，是生物防治的热门手段。拟寄生蜂在攻击时会使宿主瘫痪，因此预计只会攻击足够大的宿主来支持后代的发育。宿主资源通常会影响宿主的属性和生活史，包括大小、发育和寿命。一些人认为，由于宿主长时间暴露于寄生蜂中，资源质量的增加会导致宿主发育缓慢，从而提高寄生蜂的效率（即寄生蜂在宿主体表或体内成功繁殖的能力）。然而，这一假设并不总是得到支持，也没有考虑到宿主对资源的其他特征的变化，而这些变化可能对寄生蜂很重要（例如，宿主大小的变化已知会影响寄生蜂的效率）。在这项研究中，我们测试了宿主在发育阶段内对宿主资源的特征变化是否比宿主在发育阶段间的特征变化更能影响寄生蜂的效率和生活史。我们将在食物质量梯度上饲养的种子象甲宿主暴露给交配后的雌性寄生蜂，并在宿主的龄期和年龄结构的尺度上测量被寄生的宿主数量和寄生蜂的生活史特征。我们的研究结果表明，尽管宿主生活史受到食物质量的巨大影响，但宿主资源的质量并不会级联影响拟寄生蜂的生活史。相反，宿主在发育阶段间的生活史变化更能预测寄生蜂的效率和生活史，这表明对于拟寄生蜂来说，找到处于特定龄期的宿主比找到处于高质量资源上的宿主更为重要。
