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Defensive symbiosis in the real world -advancing ecological studies of heritable, protective bacteria in aphids and beyond
Journal article   Open access   Peer reviewed

Defensive symbiosis in the real world -advancing ecological studies of heritable, protective bacteria in aphids and beyond

Kerry M. Oliver, Andrew H. Smith and Jacob A. Russell
Functional ecology, v 28(2), pp 341-355
01 Apr 2014
DOI: https://doi.org/10.1111/1365-2435.12133
Featured in Collection :   UN Sustainable Development Goals @ Drexel
url
https://doi.org/10.1016/j.seizure.2006.09.003View
Published, Version of Record (VoR)Open Access (Publisher-Specific),  Open
url
https://doi.org/10.1111/1365-2435.12133View
Published, Version of Record (VoR) Open

Abstract

Environmental Sciences & Ecology Life Sciences & Biomedicine Science & Technology Ecology
1. Symbiotic microbes have become increasingly recognized to mediate interactions between natural enemies and their hosts. The ecologies of these symbioses, however, are poorly understood in many systems, and a predictive framework is needed to guide future studies. To achieve this, we focus on heritable, defensive microbes of insects. Our review of laboratory based studies identifies diverse bacterial species that have independently evolved to protect a range of insects against parasitoids, parasites, predators and pathogens. Although defensive mechanisms are typically unknown, some involve toxins or the upregulation of host immunity. 2. Despite substantial benefits of infection in the presence of natural enemies, the protective symbionts of insects are often found at intermediate levels in natural populations. Using a host-centred population genetics approach made possible by the host restriction and cytoplasmic inheritance of these microbes, we propose that balancing selection plays a major role in symbiont maintenance, with protective benefits in the presence of enemies and infection costs in their absence. Other mediating factors are likely to be important, including temperature, superinfections and transmission dynamics. 3. While few studies have provided evidence for defence in the field, several studies have shown symbiont infection frequencies to be dynamic, varying across temporal and spatial gradients and food-plant associations. Newly presented data from our pea aphid research reveal that temporal shifts in defensive symbiont prevalence can be quite rapid, with Hamiltonella defense showing 10-20% shifts around a seasonal average of c. 50%. Such findings contrast with more unidirectional changes seen in laboratory population cages, suggesting temporal changes in the costs and benefits of symbionts in the field. 4. To frame future research on defensive symbiont ecology, we briefly consider a range of studies needed to test laboratory- and field-derived predictions on defensive symbiosis. Included are investigations of defensive mechanisms, symbiont-driven co-evolution and community-level effects. We also consider the need for more thorough and highly resolved molecular diagnostics of natural infections, laboratory studies on functional differences between symbiont strains and species and studies on the relative costs and benefits of defenders in nature. 5. The emerging theme of symbiont-mediated defence across eukaryotes suggests that knowledge of the functional mechanisms behind protection and natural symbiont dynamics could be key to understanding many of the world's antagonistic species interactions. Thus, the development of insects as a model for such studies holds promise for these organisms and beyond.

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310 citations in Web of Science
304 citations in Scopus

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UN Sustainable Development Goals (SDGs)

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#3 Good Health and Well-Being

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Collaboration types
Domestic collaboration
Web of Science research areas
Ecology
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