Parasite Removal, but Not Herbivory, Deters Future Parasite Attachment on Tomato

Abstract

Plants face many antagonistic interactions that occur sequentially. Often, plants employ defense strategies in response to the initial damage that are highly specific and can affect interactions with subsequent antagonists. In addition to herbivores and pathogens, plants face attacks by parasitic plants, but we know little about how prior herbivory compared to prior parasite attachment affects subsequent host interactions. If host plants can respond adaptively to these different damage types, we predict that prior parasitism would have a greater deterrent effect on subsequent parasites than would prior herbivory. To test the effects of prior parasitism and prior herbivory on subsequent parasitic dodder (Cuscuta spp.) preference, we conducted two separate greenhouse studies with tomato hosts (Solanum lycopersicum). In the first experiment, we tested the effects of previous dodder attachment on subsequent dodder preference on tomato hosts using three treatments: control plants that had no previous dodder attachment; dodder-removed plants that had an initial dodder seedling attached, removed and left in the same pot to simulate parasite death; and dodder-continuous plants with an initial dodder seedling that remained attached. In the second experiment, we tested the effects of previous caterpillar damage (Spodoptera exigua) and mechanical damage on future dodder attachment on tomato hosts. Dodder attached most slowly to tomato hosts that had dodder plants previously attached and then removed, compared to control plants or plants with continuous dodder attachment. In contrast, herbivory did not affect subsequent dodder attachment rate. These results indicate that dodder preference depended on the identity and the outcome of the initial attack, suggesting that early-season interactions have the potential for profound impacts on subsequent community dynamics.

Rising from the shadows: Selective foraging in model shoot parasitic plants

“…Variation in size within host species is another factor that may influence host selection, as it was found that Cuscuta preferentially parasitises tall plants over short ones (Marquardt & Pennings, 2010). It was also observed that prior dodder parasitism and herbivory events can, depending on the host species, reduce subsequent attachment, suggesting that Cuscuta preferences may be influenced by the identity and the outcome of the initial attack, and that induced physiological changes in potential hosts may have a repellent effect on Cuscuta (Tjiurutue et al, 2016(Tjiurutue et al, , 2017. It should be pointed out that parasitism varies in intensity for a given host species between different environments, shaping its preferred status in a given location (Baráth, 2021).…”