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Herbivory is known to cause several different responses in plants, from morphological to biochemical mechanisms, as defenses against herbivore attacks. The biochemical mechanisms against herbivores are usually complex and dynamic, and can be both direct and indirect. In a recent work (Orrock et al, 2017), the authors report experiments of induced defense mechanisms against herbivores in tomato plants (Solanum lycopersicum). They show that triggering plant defenses by the application of methyl jasmonate (MeJA) induces cannibalism in caterpillars of the species Spodoptera exigua.

Induced cannibalism among herbivores may be beneficial to the plant in two ways: (i) herbivores eat less plant biomass (possibly by an alteration on palatability or leaf quality for the caterpillars), and (ii) cannibalism directly reduces herbivore abundances.

Build a hypothetical field scenario for this plant-herbivore interaction, developing and analysing an appropriate mathematical model that takes effects (i) and/or (ii) above into account. What

• Are there different approaches to introduce (i) and (ii) into population dynamics?
• How the relative strength of these two effects may influence population balance?

How would the infection by horizontally-transmitted pathogens on the caterpillar population be altered with the induction of cannibalism? What if the presence of the pathogen makes the caterpillar more prone to be eaten by its own kind? Can ou introduce these ingredients into your model in a simple way?

Induced defences in plants reduce herbivory by increasing cannibalism Orrock, J., Connolly, B. and Kitchen, A.. Nature ecology & evolution 1, no. 8 (2017): 1205. https://www.nature.com/articles/s41559-017-0231-6