Abstract
Plants are challenged by both above- and belowground herbivores which may indirectly interact with each other via herbivore-induced changes in plant traits; however, little is known about how genetic variation of the host plant shapes such interactions. We used two genotypes (M4 and E9) of Solanum dulcamara (Solanaceae) with or without previous experience of aboveground herbivory by Spodoptera exigua (Noctuidae) to quantify its effects on subsequent root herbivory by Agriotes spp. (Elateridae). In the genotype M4, due to the aboveground herbivory, shoot and root biomass was significantly decreased, roots had a lower C/N ratio and contained significantly higher levels of proteins, while the genotype E9 was not affected. However, aboveground herbivory had no effects on weight gain or mortality of the belowground herbivores. Root herbivory by Agriotes increased the nitrogen concentration in the roots of M4 plants leading to a higher weight gain of conspecific larvae. Also, in feeding bioassays, Agriotes larvae tended to prefer roots of M4 over E9, irrespective of the aboveground herbivore treatment. Fourier-Transform Infrared Spectroscopy (FT-IR) documented differences in metabolic profiles of the two plant genotypes and of the roots of M4 plants after aboveground herbivory. Together, these results demonstrate that previous aboveground herbivory can have genotype-specific effects on quantitative and qualitative root traits. This may have consequences for belowground interactions, although generalist root herbivores might not be affected when the root biomass offered is still sufficient for growth and survival.
Highlights
Both above- and below-ground plant parts are attacked by a wide array of aboveground (AG) and belowground (BG) herbivores
In 65% of the first and second leaves of the genotype M4, it was observed that S. exigua larvae chewed the petiole of the leaves thereby inducing the wilting of the leaves (Figure 1a)
Based on the previous results of protease inhibitor activity (PI) induction in leaves of S. dulcamara plants [51], we were interested to see if PIs are induced in the root tissue in response to previous shoot or root herbivory but we found no significant changes in PI levels
Summary
Both above- and below-ground plant parts are attacked by a wide array of aboveground (AG) and belowground (BG) herbivores Along with this direct interaction with the plant, these spatially and in some cases temporally separated herbivores interact with each other indirectly via their shared host plant [1,2]. The interactions are mediated by changes in plant traits such as quantitative and qualitative changes in plant primary and secondary metabolites [3,4,5] and plant growth Such interactions might be beneficial, detrimental or neutral to each other, largely depending upon the defense strategy of the plant species upon herbivory, the feeding guild, the modes of feeding, the sequence of arrival of the herbivores, and abiotic factors [5,6,7,8,9,10]. In our experiment, we used a novel approach and introduced the BG herbivores to the root system after removal of AG herbivores from the plants to test for history effects of AG herbivory mediated by changes in plant traits
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