Variability and Parasitoid Foraging Efficiency: A Case Study of Pea Aphids and <i>Aphidius ervi</i>

Ives, Anthony R.; Schooler, Shon; Jagar, Victoria J.; Knuteson, Sarah E.; Grbić, Miodrag; Settle, William H.

doi:10.1086/303269

Cited by 87 publications

(95 citation statements)

References 49 publications

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“…Since only one wasp can complete development in a single aphid, self-superparasitism (more than one egg laid by the same mother) by solitary endoparasitoids like A. ervi has generally been considered maladaptive, yet wide-ranging conditions have been proposed under which this strategy may be adaptive [51]. If the net fitness of offspring is higher under conditions of superparasitism compared to single-parasitism then selection may favor the sacrifice of an additional egg for a parasitoid such as A. ervi , which is limited by their time to find hosts rather than the number of eggs they have [25,53]. Aphidius ervi has a large number (96 to 567) of small, yolk-free eggs during adulthood (for example, [54,55]).…”

Section: Discussionmentioning

confidence: 99%

Parasitic wasp responses to symbiont-based defense in aphids

et al. 2012

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Background Recent findings indicate that several insect lineages receive protection against particular natural enemies through infection with heritable symbionts, but little is yet known about whether enemies are able to discriminate and respond to symbiont-based defense. The pea aphid, Acyrthosiphon pisum , receives protection against the parasitic wasp, Aphidius ervi , when infected with the bacterial symbiont Hamiltonella defensa and its associated bacteriophage APSE ( Acyrthosiphon pisum s econdary e ndosymbiont). Internally developing parasitoid wasps, such as A. ervi , use maternal and embryonic factors to create an environment suitable for developing wasps. If more than one parasitoid egg is deposited into a single aphid host (superparasitism), then additional complements of these factors may contribute to the successful development of the single parasitoid that emerges. Results We performed experiments to determine if superparasitism is a tactic allowing wasps to overcome symbiont-mediated defense. We found that the deposition of two eggs into symbiont-protected aphids significantly increased rates of successful parasitism relative to singly parasitized aphids. We then conducted behavioral assays to determine whether A. ervi selectively superparasitizes H. defensa -infected aphids. In choice tests, we found that A. ervi tends to deposit a single egg in uninfected aphids, but two or more eggs in H. defensa -infected aphids, indicating that oviposition choices may be largely determined by infection status. Finally, we identified differences in the quantity of the trans-β-farnesene, the major component of aphid alarm pheromone, between H. defensa -infected and uninfected aphids, which may form the basis for discrimination. Conclusions Here we show that the parasitic wasp A. ervi discriminates among symbiont-infected and uninfected aphids, and changes its oviposition behavior in a way that increases the likelihood of overcoming symbiont-based defense. More generally, our results indicate that natural enemies are not passive victims of defensive symbionts, and that an evolutionary arms race between A. pisum and the parasitoid A. ervi may be mediated by a bacterial symbiosis.

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Section: Discussionmentioning

confidence: 99%

Parasitic wasp responses to symbiont-based defense in aphids

et al. 2012

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“…One of the few studies that examined the temporal pattern in the heterogeneity of parasitism showed that there was much variation between years (Jones et al 1993). Ives et al (1999) present an alternative, suggesting that the presence of large amounts of variability reduce the importance of aggregating and functional responses that occur over small spatial scales. We would need parasitism data for several years or a functional response experiment over a wide variety of densities to fully predict the long term impact of densitydependent parasitism on the stability of the system.…”

Section: Implications For Dynamicsmentioning

confidence: 99%

Density-dependent foraging behaviors in a parasitoid lead to density-dependent parasitism of its host

2003

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Empirical studies of spatial heterogeneity in parasitism by insect parasitoids have focused largely on patterns, while the many possible underlying mechanisms have been little studied in the field. We conducted experimental and observational studies on Tachinomyia similis (Diptera: Tachinidae) attacking western tussock moths (Orgyia vetusta; Lepidoptera: Lymantriidae) on lupine bushes at Bodega Bay, Calif., USA. We examined several foraging behaviors that have been hypothesized to create density-dependent variation in parasitism rates, including spatial aggregation of parasitoids to high host density, mutual interference among searching parasitoids and decelerating functional responses of the parasitoid. At the spatial scale of individual bushes, we detected both aggregation to a high density and a decelerating functional response. The resulting spatial pattern of parasitism was best fit by two models; one included an effect of parasitoid aggregation and the other included an effect of aggregation and a decelerating functional response. Most of the variation in parasitism was not correlated with density of O. vetusta.

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“…The correlation between spatial patchiness and functional response described in this model application can also be found in terrestrial food-webs. Parasitoid insects of the pea aphid, for example, turn from a type I response to type II when aphid density and, thus, spatial crowding of host increases (Ives et al 1999). An analog shift from type I to type II functional response also appears for fox squirrels when animals gather in a larger, more patchy habitat (Morgan et al 1997).…”

Section: Resultsmentioning

confidence: 99%

Intermittency in processing explains the diversity and shape of functional grazing responses

Wirtz

2012

Oecologia

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Central to theoretical studies of trophic interactions is the formulation of the consumer response to varying food availability. Response functions, however, are only rarely derived in mechanistic ways. As a consequence, the uncertainty in the functional representation of feeding remains large, as, e.g., evident from the ongoing debate on the usage of Ivlev, or Holling type I, II, and III functions in aquatic ecosystem models. Here, I refer to the work of Sjöberg in Ecol Model 10:215-225 (1980) who proposed to apply elements of the queuing theory developed in operational research to plankton-plankton interactions. Within this frame, food item processing is subdivided into two major stages which may operate with variable synchronicity. Asynchronous phasing of the two stages enhances the probability of long total processing times. This phenomenon is here termed feeding intermittency. Intermittency is assumed to determine the functional form of grazing kinetics, for which a novel grazing function containing a "shape" parameter is derived. Using this function, I evaluate the hypotheses that intermittency is influenced by (1) patchiness in the prey field (e.g., related to turbulence), and (2) the ratio of actual prey size to optimal prey size. Evidence for the first hypothesis arises from explaining reported variations in clearance rates of Acartia tonsa under different turbulence regimes. Further model applications to ingestion data for rotifers, copepods, and ciliates support the view that an increasing food size enhances intermittency and, this way, affects functional grazing responses. In the application to ciliate grazing, a possible prey density effect appears, possibly due to an intermittent activation of a feeding sub-stage. Queueing theory offers mechanistic explanations for transitions between Holling I-, II-, and Ivlev-type grazing. In doing so for variable prey size ratios, it may also refine size-based ecosystem models which are increasingly emerging in plankton ecology.

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Variability and Parasitoid Foraging Efficiency: A Case Study of Pea Aphids and Aphidius ervi

Cited by 87 publications

References 49 publications

Parasitic wasp responses to symbiont-based defense in aphids

Parasitic wasp responses to symbiont-based defense in aphids

Density-dependent foraging behaviors in a parasitoid lead to density-dependent parasitism of its host

Intermittency in processing explains the diversity and shape of functional grazing responses

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