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--- 2018:groups:g6:start [2017/12/13 22:22] – maciel
+++ 2018:groups:g6:start [2024/01/09 18:45] (current) – external edit 127.0.0.1
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 **Group 6**
-====== Inducible defences in intraguild predation systems ======
+====== Too big to gobble: inducible defences in intraguild predation systems ======
 Wiki site of the practical exercise of the [[http://www.ictp-saifr.org/mathbio7|VII Southern-Summer School on Mathematical Biology]].
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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.
+When predation risk is high, 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. These so-called //inducible defences// can have major effects on the dynamics of interacting species.
-{{ :2018:groups:g6:intraguild_predation.png?250 |}}
+Kratina et al. (2010) studied the dynamics of an experimental food web consisting of the unicellular algae //Rhodomonas minuta// which is consumed by both the turbelarian flatworm, //Stenostomum virginianum//, and hypotrich ciliates of the genus //Euplotes// spp., while the latter is also eaten by the turbelarian flatworm.
-**Fig. 1.** The intraguild predation community module.
+{{:2018:groups:g6:euplotes.jpg?380 | }}
+The presence of predatory flatworms induces a change in morphology of //Euplotes//, considerably increasing 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 //Euplotes// in this system.
-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, //Stenostomum virginianum//, (intraguild predator), 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 increase the persistence of the intraguild prey.
+//Figure: Normal and induced morphs of //Euplotes octocarinatus//. Scale bar is 40 microns. Figure taken from [[http://web.uvic.ca/~banholt/anhlabsite/id.html|here]]. //
-{{ :2018:groups:g6:euplotes.jpg?360 |}}
-**Fig. 2.** Normal and induced morphs of //Euplotes octocarinatus//. Scale bar is 40 microns. Figure taken from [[http://web.uvic.ca/~banholt/anhlabsite/id.html|this place]].
-===== Assignment =====
+{{ :2018:groups:g6:intraguild_predation.png?240}}
+This system is an instance of one of the basic three-species community modules: //intraguild predation//. 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) - see figure. One of the challenges of these systems is to find robust conditions for persistence of all three species - they are ubiquitous in nature, but are usually restricted to narrow parameter ranges in models!
-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 increase the persistence of the intraguild prey? If so, are there conditions on the parameters of the model?
-===== Extensions =====
+===== Assignment =====
+Develop and analyze a model for the population dynamics of the system described, taking into account inducible defences of the //Euplotes// prey, and use it to explore the consequences of this defence mechanism.
-  * It is quite reasonable to assume that individuals that assume an altered form can have a decrease foraging efficiency, as pointed out in the Discussion of Kratina et al (2010). What are the effects of this trade-off in the dynamics?
+===== Questions and suggestions =====
+  * Do inducible defences enhance the persistence of the intraguild prey? What are the conditions or parameter values that allow persistence?
+  * It is quite reasonable to assume that induced morphs individuals might have a decreased foraging efficiency, as pointed out in Kratina et al (2010). What are the effects of this trade-off in the dynamics?
+==== Challenge ====
+  * Inducible defences are not free: they incur extra developmental costs. Assuming a small cost, is it advantageous to have these defences? That is, could it be better to be always small or always big? Under what circumstances?
 ===== Reference =====
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 ]]
-===== Results =====