Laboratory of Insect Natural Enemies, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka, 819-0395, Japan.
Guangdong Key Laboratory for Innovation Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, 510642, China.
Sci Rep. 2021 Dec 1;11(1):23215. doi: 10.1038/s41598-021-02713-1.
In an assemblage of multiple predators sharing a single prey species, the combined effects of the component species may scale unpredictably because of emergent interspecific interactions. Prior studies suggest that chaotic but persistent community dynamics are induced by intra-/interspecific interactions between native and nonnative parasitoids competing over a shared host. Here, we test the impact of the nonnative parasitoid Heterospilus prosopidis (Hymenoptera: Braconidae) on the intraspecific interference and offspring sex ratio of the native parasitoid Anisopteromalus calandrae (Hymenoptera: Pteromalidae). We found that the nonnative parasitoid reduced intraspecific interference among native parasitoids and decreased the proportion of female offspring produced by the native parasitoid (predicted under conditions of reduced host availability). At higher host densities, the nonnative parasitoid contributed less to the total proportion of hosts parasitized, as its innate saturating Type II response changed to a dome-shaped Type IV response with increasing density of the native parasitoid, while the native parasitoid retained its increasing Type I response. This inverse host-density-dependent response between the two parasitoids and associated competitive superiority can explain the observed changes in parasitism; at high host densities, the searching efficiency of the native parasitoid increases via host feeding while the nonnative parasitoid experiences egg limitation. These results highlight the importance of the complementary top-down effects of multiple consumers on a single resource.
在多个捕食者共享单一猎物物种的集合中，由于种间相互作用的出现，组合物种的综合效应可能不可预测地扩大。先前的研究表明，由于竞争同一宿主的本地和非本地寄生蜂之间的种内/种间相互作用，会导致混沌但持续的群落动态。在这里，我们测试了非本地寄生蜂 Heterospilus prosopidis（膜翅目：Braconidae）对本地寄生蜂 Anisopteromalus calandrae（膜翅目：Pteromalidae）种内干扰和后代性别比例的影响。我们发现，非本地寄生蜂减少了本地寄生蜂之间的种内干扰，并降低了本地寄生蜂产生的雌性后代比例（在宿主可利用性降低的情况下预测）。在更高的宿主密度下，由于其先天饱和的 II 型反应随着本地寄生蜂密度的增加而变为穹顶状的 IV 型反应，非本地寄生蜂对总寄生宿主比例的贡献较小，而本地寄生蜂保留了其不断增加的 I 型反应。这两种寄生蜂之间的这种与宿主密度相关的反向反应以及相关的竞争优势可以解释观察到的寄生变化；在高宿主密度下，本地寄生蜂通过宿主取食增加了搜索效率，而非本地寄生蜂则受到卵的限制。这些结果强调了多个消费者对单一资源的互补自上而下影响的重要性。
