一些植物物种在植物化学物质中表现出极高的种内多样性(=化学多样性)。正如关于生物多样性的讨论,更高的化学多样性可以提供更好的保护免受环境压力,包括食草动物.然而,对于植物个体对草食动物的抗性主要是由其自身的化学多样性还是由特定邻居提供的关联抗性所控制的,人们知之甚少。为了研究化学多样性在植物-蚜虫相互作用中的作用,我们用了菊科菊科,其个体在叶萜类化合物的组成上明显不同,形成不同的化学型。在由包含五个相同或不同化学型的个体的地块组成的田地中建立植物。有翼蚜虫的存在,表明吸引力,和丰富的有翼和无翼蚜虫,表明健康,每周对每株植物进行计数。在蚜虫的高峰期,从所有植物中采集叶片样品,用于重新分析萜类化合物的组成和萜类化合物化学多样性的定量,以单个植物计算(香农指数,Hsind,也被认为是α-化学多样性)和情节水平(Hsplot,=β-化学多样性)。蚜虫的吸引力既不受化学类型也不受情节类型的影响。在此设置中,实时气味环境可能非常复杂,阻碍明确的偏好。相比之下,丰度受化学类型和地块类型的影响。平均而言,与异质地块相比,在同质生长的两种化学类型的植物上发现了更多的Uroleucontanaceti蚜虫,支持联想阻力假说。对于大虹吸管,在一种化学类型上,存在的可能性在地块类型之间有所不同。以梯度表示的萜类化学多样性揭示了Hsplot对U.tanaceti的负影响,但Hsind与坦乙菌丰度呈正相关。福斯考维脲的蚜虫不受任何化学多样性水平的影响。总之,这项研究表明,不仅单个植物的化学型和化学多样性,而且特定邻居的化学型和化学多样性也会影响某些植物与草食动物的相互作用。这些作用在植物化学型方面具有高度特异性,并且在蚜虫物种和它们的形态之间有所不同(有翼与没有翅膀)。此外,我们的研究结果突出了分析不同水平的化学多样性的重要性。
Some plant species express an extraordinarily high intraspecific diversity in phytochemicals (= chemodiversity). As discussed for biodiversity, higher chemodiversity may provide better protection against environmental stress, including herbivory. However, little is known about whether the resistance of a plant individual towards herbivores is mostly governed by its own chemodiversity or by associational resistance provided by conspecific neighbours. To investigate the role of chemodiversity in plant-aphid interactions, we used the Asteraceae Tanacetum vulgare, whose individuals differ pronouncedly in the composition of leaf terpenoids, forming distinct chemotypes. Plants were set up in a field consisting of plots containing five individuals of either the same or different chemotypes. Presence of winged aphids, indicating attraction, and abundance of winged and unwinged aphids, indicating fitness, were counted weekly on each plant. During the peak abundance of aphids, leaf samples were taken from all plants for re-analyses of the terpenoid composition and quantification of terpenoid chemodiversity, calculated on an individual plant (Shannon index, Hsind, also considered as α-chemodiversity) and plot level (Hsplot, = β-chemodiversity). Aphid attraction was neither influenced by chemotype nor plot-type. The real-time odour environment may be very complex in this setting, impeding clear preferences. In contrast, the abundance was affected by both chemotype and plot-type. On average, more Uroleucon tanaceti aphids were found on plants of two of the chemotypes growing in homogenous compared to heterogenous plots, supporting the associational resistance hypothesis. For Macrosiphoniella tanacetaria aphids, the probability of presence differed between plot-types on one chemotype. Terpenoid chemodiversity expressed as a gradient revealed negative Hsplot effects on U. tanaceti, but a positive correlation of Hsind with M. tanacetaria abundance. Aphids of M. fuscoviride were not affected by any level of chemodiversity. In conclusion, this study shows that not only the chemotype and chemodiversity of individual plants but also that of conspecific neighbours can influence certain plant-herbivore interactions. These effects are highly specific with regard to the plant chemotype and differ between aphid species and their morphs (winged vs. unwinged). Furthermore, our results highlight the importance of analysing chemodiversity at different levels.