Data from: Root-lesion nematodes suppress cabbage aphid population development by reducing aphid daily reproduction

Empirical studies have shown that belowground feeding herbivores can affect the performance of aboveground herbivores in different ways. Often the critical life-history parameters underlying the observed performance effects remain unexplored. In order to better understand the cause for the observed effects on aboveground herbivores, these ecological mechanisms must be better understood. In this study we combined empirical experiments with a modelling approach to analyse the effect of two root feeding endoparasitic nematodes with different feeding strategies on the population growth of the aboveground feeding specialist aphid Brevicoryne brassicae on Brassica nigra. The aim was to test whether emerging differences in life history characteristics (days until reproduction, daily reproduction) would be sufficient to explain observed differences in aphid population development on plants with and without two species of nematodes. Aphid numbers were lower on plants with Pratylenchus penetrans in comparison to aphid numbers on plants with Meloidogyne spp. A dedicated experiment showed that aphid daily reproduction was lower on plants with P. penetrans (3.08 offspring per female per day) in comparison to both uninfested plants and plants with Meloidogyne spp. (3.50 offspring per female per day). The species-specific reduction of aphid reproduction appeared independent of changes in amino acids, soluble sugars or the glucosinolate sinigrin in the phloem. An individual-based model revealed that relatively small differences in reproduction rate per female were sufficient to yield a similar difference in aphid populations as was found in the empirical experiments.

已有实证研究表明，地下取食植食性动物（belowground feeding herbivores）可通过多种途径影响地上取食植食性动物（aboveground herbivores）的生存表现，但现有研究往往未深入探究驱动上述表现差异的关键生活史参数。为更好地阐明地上植食性动物表现受影响的内在机制，需先明确相关生态学过程。本研究结合实证实验与建模方法，分析了两种取食策略各异的根系内寄生线虫（endoparasitic nematodes）对黑芥（Brassica nigra）上专食性蚜虫甘蓝蚜（Brevicoryne brassicae）种群增长的影响。研究旨在验证：生活史特征（如生殖前期天数、日均生殖量）的差异是否足以解释有/无两种线虫侵染的植株上蚜虫种群动态的观测差异。相较于接种根结线虫属（Meloidogyne spp.）的植株，接种短体线虫（Pratylenchus penetrans）的植株上蚜虫种群数量更低。专项实验进一步显示，与未侵染植株及接种根结线虫属的植株相比，接种短体线虫的植株上蚜虫日均生殖量更低（每雌每日3.08头若虫），后两者的日均生殖量均为3.50头若虫。蚜虫生殖量的物种特异性降低，似乎与韧皮部（phloem）中氨基酸、可溶性糖及硫代葡萄糖苷（glucosinolate）黑芥子苷（sinigrin）的含量变化无关。基于个体的模型（individual-based model）结果表明，单雌生殖率的微小差异，即可导致与实证实验中观测到的蚜虫种群差异相一致的结果。