Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic.
Biology Centre of the Czech Academy of Sciences, Institute of Entomology, České Budějovice, Czech Republic.
J Anim Ecol. 2022 Sep;91(9):1929-1939. doi: 10.1111/1365-2656.13782. Epub 2022 Jul 31.
Ecological communities are composed of many species, forming complex networks of interactions. Current environmental changes are altering the structure and species composition of ecological networks, which could modify interactions, either directly or indirectly. To predict changes in the functioning of communities, we need to understand whether species interactions are primarily driven by network structure (i.e. topology) or the specific identities of species (i.e. nodes). Yet, this partitioning of effects is challenging and thus rarely explored. Here we disentangled the influence of network structure and the identities of species on the outcome of consumer-resource interactions using a host-parasitoid system. We used four common community modules in host-parasitoid communities to represent network structure (i.e. host-parasitoid, exploitative competition, alternative host and a combination of exploitative competition and alternative host). We assembled nine different species combinations per community module in a laboratory experiment using a pool of three Drosophila hosts and three larval parasitoid species (Leptopilina sp., Ganaspis sp. and Asobara sp.). We compared host suppression and parasitoid performance across community modules and species assemblages to identify general effects linked to network structure and specific effects due to species community composition. We found that multiple parasitoid species enhanced host suppression due to sampling effect, weaker interspecific than intraspecific competition between parasitoids, and synergism. However, the effects of network structure on parasitoid performance were species specific and dependent on the identity of co-occurring species. Consequently, multiple parasitoid species generally strengthen top-down control, but the performance of the parasitoids depends on the identity of either the co-occurring parasitoid species, the alternative host species or both. Our results highlight the importance of preserving parasitoid diversity for ecosystem functioning and show that other effects depend on species community composition, and may therefore be altered by ongoing environmental changes.
生态群落由许多物种组成，形成了复杂的相互作用网络。当前的环境变化正在改变生态网络的结构和物种组成，这可能会改变相互作用，无论是直接的还是间接的。为了预测群落功能的变化，我们需要了解物种相互作用是主要由网络结构（即拓扑结构）还是物种的特定身份（即节点）驱动的。然而，这种效果的划分具有挑战性，因此很少被探索。在这里，我们使用一种宿主-寄生系统来分离网络结构和物种身份对消费者-资源相互作用结果的影响。我们使用宿主-寄生群落中的四个常见群落模块来代表网络结构（即宿主-寄生、掠夺性竞争、替代宿主和掠夺性竞争与替代宿主的组合）。我们在实验室实验中使用三个果蝇宿主和三个幼虫寄生蜂物种（Leptopilina sp.、Ganaspis sp.和 Asobara sp.）的一个池，为每个群落模块组装了九个不同的物种组合。我们比较了群落模块和物种组合之间的宿主抑制和寄生蜂表现，以确定与网络结构相关的一般效应和由于物种群落组成而产生的特定效应。我们发现，由于抽样效应，多个寄生蜂物种增强了宿主抑制作用，寄生蜂之间的种间竞争比种内竞争弱，并且存在协同作用。然而，网络结构对寄生蜂表现的影响是物种特异性的，并且取决于共存物种的身份。因此，多个寄生蜂物种通常会增强自上而下的控制，但寄生蜂的表现取决于共存的寄生蜂物种、替代宿主物种或两者的身份。我们的结果强调了保护寄生蜂多样性对生态系统功能的重要性，并表明其他效应取决于物种群落组成，并且可能因此受到正在发生的环境变化的影响。
