Plant genotypic diversity effects on soil nematodes vary with trophic level

At local spatial scales, loss of genetic diversity within species can lead to species loss. Few studies, however, have examined plant genotypic diversity effects across trophic levels.

We investigated genotypic diversity effects of Phragmites australis on belowground biomass and soil nematode communities.

Our results revealed belowground plant biomass and nematode abundance responses to plant genotypic diversity were uncoupled. Decreasing plant genotypic diversity decreased the abundance of lower, but not higher trophic level nematodes. Low plant genotypic diversity also decreased the structural footprint and functional indices of nematodes, indicating lowered metabolic functioning of higher-trophic level nematodes and decreased soil food web stability.

Our study suggests that plant genotypic diversity effects differ across trophic levels, taxonomic groups, and ecosystem functions and that decreasing plant genotypic diversity could destabilize belowground food webs. This highlights the importance of conserving intraspecific plant diversity.

Methods
Belowground plant material was washed immediately, oven dried at 50°C to constant weight and weighed. Nematodes were counted, identified (100 randomly-selected individuals per plot or all individuals if fewer than 100) to genus level using ×1000 magnification and classified into four feeding groups. Nematode abundance was expressed as individuals per 100 g dry weight (DW) soil, diversity was expressed as the genera richness and Shannon–Wiener Diversity Index at the genus level (H′ diversity).

在局地空间尺度上，物种内遗传多样性的丧失可能引发物种灭绝。然而，鲜有研究探讨植物基因型多样性（Genotypic Diversity）对不同营养级的影响。

本研究探讨了芦苇（Phragmites australis）的基因型多样性对地下生物量与土壤线虫群落的影响。

研究结果显示，植物地下生物量与线虫丰度对植物基因型多样性的响应存在解耦现象。植物基因型多样性降低会导致低营养级线虫的丰度下降，但对高营养级线虫无显著影响。低植物基因型多样性还会降低线虫的结构足迹指数与功能指数，表明高营养级线虫的代谢功能受损，土壤食物网稳定性下降。

本研究表明，植物基因型多样性的影响因营养级、类群及生态系统功能而异，且植物基因型多样性的降低可能破坏地下食物网的稳定性。这凸显了保护植物种内多样性的重要性。

方法

地下植物材料经即刻冲洗后，置于50℃烘箱中烘干至恒重并称量。对线虫进行计数，并在1000倍放大倍数下鉴定至属级（每个样方随机选取100个个体，若个体数不足100则全部鉴定），随后划分为4个取食类群。线虫丰度以每100g干重（DW，Dry Weight）土壤中的个体数表示，多样性则以属级丰富度及香农-威纳多样性指数（Shannon–Wiener Diversity Index，H′多样性）表征。