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Group 6
Inducible defences in intraguild predation systems
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Introduction
Under the risk of predation many prey species employ defence mechanisms that potentially reduce their chances of being consumed. These mechanisms can involve shifts in the morphology, physiology , life-history and/or behaviour of prey species. Inducible defences can have major effects on the dynamics of interacting species. In particular, they have shown to stabilize predator-prey models. The goal of this project is to study the effects of inducible defences on the dynamics of intraguild predation.
Fig. 1. The intraguild predation community module.
Intraguild predation is one of the basic three species community modules. It is composed of two consumers that share a common resource and one of the consumers (the intraguild predator) can prey on its competitor (the intraguild prey). Kratina et al (2010) studied the dynamics of a experimental food web consisting of the turbelarian flatworm (intraguild predator), Stenostomum virginianum, hypotrich ciliates of the genus Euplotes spp. (intraguild prey) and the unicellular algae Rhodomonas minuta (basal resource). The presence of predatory flatworms induces a change in morphology of Euplotes that considerably increases its size. These defended altered forms then have a reduced risk of being eaten by the gape-limited predators. By selecting Euplotes clones with high and low inducibility the authors show that inducible defences enhance persistence of the intraguild prey in this system.
Fig. 2. Normal and induced morphs of Euplotes octocarinatus. Scale bar is 40 microns. Figure taken from this place.
Assignment
Develop an ordinary differential equations model for intraguild predation that takes into account inducible defences on the intraguild prey. Can you show that inducible defences enhance the persistence of the intraguild prey? If so, what are the conditions on the parameters of the model?
Extension
It is quite reasonable to assume that induced morphs individuals might have a decreased foraging efficiency, as pointed out in the Discussion of Kratina et al (2010). What are the effects of this trade-off in the dynamics?