Trophic assimilation efficiency markedly increases at higher trophic levels in four-level host-parasitoid food chain.
Trophic assimilation efficiency markedly increases at higher trophic levels in four-level host-parasitoid food chain.
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DOI：
10.1098/rspb.2015.3043
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发表时间：
2016-03-16
期刊：
影响因子：
--
通讯作者：
van Veen FJ
中科院分区：
文献类型：
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作者：
Sanders D;Moser A;Newton J;van Veen FJ
营养同化效率（资源生物量转化为消费者生物量）被认为是自然群落食物链长度的限制因素。在占陆地消费者相互作用的大部分的寄主-寄生物系统中，由于寄主组织的资源组成与消费者的资源需求密切匹配，因此在较高的营养水平上可能会出现较高的营养同化效率，这将允许更长的食物链。我们测量了沿着蚜虫-初级-次级-第三级寄生蜂食物链的生物量转移效率，并使用稳定同位素分析来确认营养水平。我们展示了沿食物链的生物质转移的高效率。从第三到第四营养级，三种次生寄生蜂的寄主生物量转移比例分别为45%、65%和73%。对于可以在第四和第五营养级发挥作用的两种寄生蜂物种，我们发现在较高营养级时营养同化效率显着增加，分别从 45% 增加到 63% 和 73% 到 93%。与其他食物链一样，δ15N随着营养级的增加而增加，从初级寄生蜂到内寄生和外寄生次级寄生蜂的营养判别因子（Δ15N）分别为1.34和1.49‰，从次级寄生蜂到三级寄生蜂的营养判别因子（Δ15N）分别为0.78‰。由于超寄生蜂的效率极高，寄主-寄生蜂群落中可能存在神秘的较高营养级，这可能会改变我们对这些重要系统群落结构的动态和驱动因素的理解。
Trophic assimilation efficiency (conversion of resource biomass into consumer biomass) is thought to be a limiting factor for food chain length in natural communities. In host–parasitoid systems, which account for the majority of terrestrial consumer interactions, a high trophic assimilation efficiency may be expected at higher trophic levels because of the close match of resource composition of host tissue and the consumer's resource requirements, which would allow for longer food chains. We measured efficiency of biomass transfer along an aphid-primary–secondary–tertiary parasitoid food chain and used stable isotope analysis to confirm trophic levels. We show high efficiency in biomass transfer along the food chain. From the third to the fourth trophic level, the proportion of host biomass transferred was 45%, 65% and 73%, respectively, for three secondary parasitoid species. For two parasitoid species that can act at the fourth and fifth trophic levels, we show markedly increased trophic assimilation efficiencies at the higher trophic level, which increased from 45 to 63% and 73 to 93%, respectively. In common with other food chains, δ15N increased with trophic level, with trophic discrimination factors (Δ15N) 1.34 and 1.49‰ from primary parasitoids to endoparasitic and ectoparasitic secondary parasitoids, respectively, and 0.78‰ from secondary to tertiary parasitoids. Owing to the extraordinarily high efficiency of hyperparasitoids, cryptic higher trophic levels may exist in host–parasitoid communities, which could alter our understanding of the dynamics and drivers of community structure of these important systems.