Simulated herbivory induces extrafloral nectary production in Prunus avium

Abstract

1. Induced chemical responses to herbivory have been widely documented, however less attention has been given to the induced morphological defences, particularly those that mediate protection mutualisms. One of the most widely studied mutualisms is the ant-plant protection mutualism, in which ants and other predatory arthropods defend plants against herbivores in exchange for food or housing. 2. Chemical and morphological traits that mediate this protection mutualism attract beneficial partners to plants. Thus induction of traits can lead to greater protection by mutualists when herbivores are present. In this study we examined whether extrafloral nectaries (EFNs) are induced in response to simulated herbivory in Prunus avium. 3. In a greenhouse experiment, continuous damage to seedlings was simulated in two treatments intended to mimic different types of herbivores: (i) 50% of the area of each leaf was removed using a paper hole punch (e.g. insect herbivore simulation), and (ii) 50% of the area of each leaf was removed using scissors (e.g. browsing mammal simulation). Seedlings in the control group were not damaged. 4. Post-treatment, damaged plants produced significantly more EFNs per leaf on pre-existing leaves, as well as those that emerged following the onset of damage, than plants in the control group. Regardless of treatment, leaves emerging earlier supported fewer EFNs than leaves emerging later in the experiment. 5. Allocation to defence by seedlings, which have limited resources available, suggests the protection mutualism could be important to plant fitness in the field. Further study of patterns of EFN induction in P. avium seedlings is needed to better understand the significance of this induced response.