Cost-Benefit Model for the Induction of an Antipredator Defense

Abstract

The production of neck spines by Daphnia pulex in response to the presence of predatory Chaoborus larvae entails a demographic cost as well as a benefit in reducing predation. I develop a model that quantitatively analyzes the costs and benefits of defensive spine formation in D. pulex by modifying life tables of both the spined (SM) and typical (TM) morphs of this prey to account for the effects of different levels of Chaoborus predation on population growth rate. At low Chaoborus densities the population growth rate (and thus fitness) of TM exceeds that of SM and spine formation is therefore disadvantageous in the population. Above a critical Chaoborus density, however, the opposite is true and spine formation is favored. The exact value for this critical Chaoborus density is influenced by both food availability for Daphnia and the degree of spatial overlap between predator and prey. The model predicts that spine induction is more advantageous under relatively poor food conditions, which suggests that the cost of this antipredator defense may not be an energy loss, but merely a lengthening of the developmental process in spined instars. The model also predicts that any predator or prey behavior that reduces spatial overlap between the two species in nature will make the formation of defensive spines less advantageous.

Reproduction of Daphnia pulex in a Northern Italy pond

“…There is indication that the production of neckteeths must occur during embryonic development, involve substantial strengthening of the carapace, may have demographic costs and may be poorly adaptive in other ways (Weber and Declerck, 1997;Wiebke et al, 2005;Juracka et al, 2011). The production of neckteeths appears to reduce the amount of resources for eggs and females exposed to Chaoborus kairomones usually tend to mature later, at larger size, and to produce fewer but larger newborn (Luning, 1992;Spitze, 1991;Riessen, 1992;Spitze, 1992;Tollrian, 1995;Weber and Declerck, 1997;Agrawal et al, 1999;Riessen, 1999;Boeing, 2006). Demographic costs linked to the production of neckteeths might further explain the density peak observed in the Bodrio del pastore III population in spring 2013, when most individuals were neckteeth-less.…”

Comparing and contrasting development and reproductive strategies in the pupal hyperparasitoids Lysibia nana and Gelis agilis (Hymenoptera: Ichneumonidae)

“…The relative importance of trade-offs in life-history traits critically depends on the quality of the habitat in which the organism lives, feeds and reproduces, in terms of resource availability (Pexton and Mayhew 2002;Holomuzki and Biggs 2006). Further, the risk of mortality experienced by the organism early during development may also influence metabolic investment towards maintenance or reproduction (Black and Dodson 1990;Riessen 1992;Vollrath and Parker 1992). Ultimately, life-history trade-offs may play an important role in shaping the structure of ecological communities (Bonsall et al 2004).…”

Methyl jasmonate‐induced nicotine production in Nicotiana attenuata: inducing defenses in the field without wounding

“…These studies have established that in many of these systems, induced responses -such as the diel vertical migration of zooplankton (Loose & Dawidowicz, 1994;Lampert, 1989) -or induced spines (Harvell, 1986;Riessen, 1992) -decrease the susceptibility of prey to predators after a prior encounter with a predator and that in the absence of predators the induced 214 responses can have fitness costs. The rapid progress in testing the cost-benefit model in these systems has in large part been possible because the induced responses can be elicited with kairomones from the predator and, therefore, without damaging the prey.…”