Resistance is costly: trade-offs between immunity, fecundity and survival in the pea aphid

Gwynn, D. M.; Callaghan, Amanda; Gorham, James D.; Walters, K. F. A.; Fellowes, Mark D. E.

doi:10.1098/rspb.2005.3089

Cited by 98 publications

(72 citation statements)

References 37 publications

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“…Do fitness costs to infection keep the symbiont at intermediate frequencies in field populations? Previously, Gwynn et al (2005) reported a trade-off between A. pisum fecundity and resistance to A. ervi, but these authors did not link either parasitoid resistance or reduced fecundity to infection with SS. Fitness costs to Hamiltonella infection are not evident in the direct estimates of fitness parameters reported in this study (table 1).…”

Section: Discussionmentioning

confidence: 99%

Population dynamics of defensive symbionts in aphids

et al. 2007

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Vertically transmitted micro-organisms can increase in frequency in host populations by providing net benefits to hosts. While laboratory studies have identified diverse beneficial effects conferred by inherited symbionts of insects, they have not explicitly examined the population dynamics of mutualist symbiont infection within populations. In the pea aphid, Acyrthosiphon pisum, the inherited facultative symbiont, Hamiltonella defensa, provides protection against parasitism by the wasp, Aphidius ervi. Despite a high fidelity of vertical transmission and direct benefits of infection accruing to parasitized aphids, Hamiltonella remains only at intermediate frequencies in natural populations. Here, we conducted population cage experiments to monitor the dynamics of Hamiltonella and of another common A. pisum symbiont, Serratia symbiotica, in the presence and absence of parasitism. We also conducted fitness assays of Hamiltonellainfected aphids to search for costs to infection in the absence of parasitism. In the population cages, we found that the frequency of A. pisum infected with Hamiltonella increased dramatically after repeated exposure to parasitism by A. ervi, indicating that selection pressures from natural enemies can lead to the increase of particular inherited symbionts in insect populations. In our laboratory fitness assays, we did not detect a cost to infection with Hamiltonella, but in the population cages not exposed to parasitism, we found a significant decline in the frequency of both Hamiltonella and Serratia. The declining frequencies of Hamiltonella-infected aphids in population cages in the absence of parasitism indicate a probable cost to infection and may explain why Hamiltonella remains at intermediate frequencies in natural populations.

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Section: Discussionmentioning

confidence: 99%

Population dynamics of defensive symbionts in aphids

et al. 2007

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“…In the pea aphid, the evidence for trade-offs is ambiguous. Ferrari et al (2001) detected no significant relationship between fecundity and susceptibility to the parasitoids, Aphidius ervi and Aphidius eadyi, but Gwynn et al (2005) found that clones with a high fecundity were more susceptible to A. ervi.…”

Section: Introductionmentioning

confidence: 97%

“…S. symbiotica and H. defensa were shown to increase the resistance of pea aphids to their parasitoid A. ervi (Oliver et al 2003(Oliver et al , 2006. This led Gwynn et al (2005) to suggest that if harbouring such bacteria bears some cost (Chen et al 2000), the negative relationship between resistance and fecundity in their pea aphid clones may be mediated by secondary symbionts, although the aphids were not tested for their presence.…”

Section: Introductionmentioning

confidence: 99%

Genetic variation and covariation of susceptibility to parasitoids in the aphid Myzus persicae : no evidence for trade-offs

et al. 2008

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Parasitoids are an important mortality factor for insects. Susceptibility to parasitoids should thus be under strong negative selection. Nevertheless, ample genetic variation for susceptibility to parasitoids is commonly observed in natural populations, suggesting that trade-offs may constrain the evolution of reduced susceptibility. This can be studied by assessing genetic variation for susceptibility and its covariation with other components of fitness. In a set of 17 clones of the peach potato aphid, Myzus persicae, for which good estimates of heritable variation for life-history traits were available, we found significant clonal variation for susceptibility to two of their common parasitoids: Aphidius colemani and Diaeretiella rapae. One clone, the only one harbouring a facultative endosymbiotic bacterium, Regiella insecticola, was entirely resistant to both parasitoids. Susceptibilities to the two parasitoids exhibited a positive genetic correlation close to unity, implying a general mechanism of defence. However, the susceptibility to parasitoids was uncorrelated to the clones' fecundity or rate of increase, providing no evidence for costs of the ability to resist parasitoids.

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“…This cost of resistance has been shown in the pea aphid (Acrythosiphon pisum), which can be controlled through introduction of the endoparasitic wasp Aphidius ervi. Gwynn and colleagues (32) found that aphids that were resistant (using a symbiotic bacteria that induces death of the parasitoid eggs) were significantly larger than sensitive phenotypes and that there was a positive relationship between fecundity and susceptibility to parasitoid attack. They conclude that ''aphids can either invest in defence or reproduction.''…”

Section: Reportmentioning

confidence: 99%