Effects of microbivore species composition and basal resource enrichment on trophic-level biomasses in an experimental microbial-based soil food web
Effects of microbivore species composition and basal resource enrichment on trophic-level biomasses in an experimental microbial-based soil food web
复制标题
微生物物种组成和基础资源富集对实验微生物土壤食物网中营养级生物量的影响
作者：
J. Mikola
摘要 先前的理论和经验证据表明，营养级内的物种组成可能深刻影响营养级生物量对增强基础资源的响应。为了测试食微生物线虫的物种组成是否对基于微生物的土壤食物网产生这样的影响，我创建了三个微观食物网，包括细菌、真菌、细菌喂养线虫（Acrobeloides tricornus、Caenorhabditis elegans）、真菌喂养线虫（Aphelenchus avenae、Aphelenchoides sp.）和捕食性线虫（Prionchulus）点状）。第二营养级食物网的物种组成有所不同：食物网A包括三角角蚁和Aph。 avenae，食物网 B 包括线虫和滑刃线虫，食物网 AB 包括所有四个物种。我通过向每个食物网的一半复制品中添加葡萄糖来增加基础资源，并在为期 22 周的实验中对微观世界进行破坏性采样四次，以估计每个营养级生物体的生物量。微生物物种组成显着影响食细菌动物和食真菌生物量，但不影响细菌、真菌或捕食者生物量。最大的食菌动物和食真菌生物生物量出现在食物网 A 中，中间生物量出现在食物网 AB 中，最小生物量出现在食物网 B 中。基础资源的添加增加了微生物和食微生物动物的生物量，但不影响捕食者生物量。重要的是，微生物物种组成并没有显着改变额外资源对营养级生物量的影响。竞争者的存在降低了三角角 A. tricornus 和 Aph. 的生物量。燕麦，因为这些物种的生物量在食物网AB中低于食物网A中，而线虫和滑刃线虫的生物量则低于食物网A中的生物量。没有受到潜在竞争对手的影响。 Aph 的生物量。仅在没有竞争者的情况下，燕麦随着额外资源的增加而增加，而三角角 A. tricornus 和 Aphelenchoides sp 的生物量则增加。在竞争对手面前也有所增加。结果表明，微生物物种组成可能决定简单微生物-线虫食物网中的二级生物量，但可能不会显着影响其他级别的生物量或改变营养级生物量对增加基础资源的响应。研究还表明，即使捕食在食物网中的作用减弱，生物体对资源可用性增加的积极反应仍然可能受到竞争的阻碍。
Abstract Previous theoretical and empirical evidence suggests that species composition within trophic levels may profoundly affect the response of trophic-level biomasses to enhanced basal resources. To test whether species composition of microbivorous nematodes has such an effect in microbial-based soil food webs, I created three microcosm food webs, consisting of bacteria, fungi, bacterial-feeding nematodes (Acrobeloides tricornus, Caenorhabditis elegans), fungal-feeding nematodes (Aphelenchus avenae, Aphelenchoides sp.) and a predatory nematode (Prionchulus punctatus). The food webs differed in species composition at the second trophic level: food web A included A. tricornus and Aph. avenae, food web B included C. elegans and Aphelenchoides sp., and food web AB included all four species. I increased basal resources by adding glucose to half of the replicates of each food web, and sampled microcosms destructively four times during a 22-week experiment to estimate the biomass of organisms at each trophic level. Microbivore species composition significantly affected bacterivore and fungivore biomass but not bacterial, fungal or predator biomass. Greatest bacterivore and fungivore biomass was found in food web A, intermediate biomass in food web AB, and smallest biomass in food web B. Basal resource addition increased the biomass of microbes and microbivores but did not affect predator biomass. Importantly, microbivore species composition did not significantly modify the effect of additional resources on trophic-level biomasses. The presence of a competitor reduced the biomass of A. tricornus and Aph. avenae, in that the biomass of these species was less in food web AB than in food web A, whereas the biomass of C. elegans and Aphelenchoides sp. was not affected by their potential competitors. The biomass of Aph. avenae increased with additional resources in the absence of the competitor only, while the biomass of A. tricornus and Aphelenchoides sp. increased also in the presence of their competitors. The results imply that microbivore species composition may determine the second-level biomass in simple microbe-nematode food webs, but may not significantly affect biomass at other levels or modify the response of trophic-level biomasses to enhanced basal resources. The study also shows that even if the role of predation in a food web is diminished, the positive response of organisms to increased resource availability may still be hindered by competition.