Benefits and costs of hosting facultative symbionts in plant‐sucking insects: A meta‐analysis

Abstract

Animal associations with microbes are widespread across the natural world and can play key roles in the biology of their hosts.Thanks to important innovations in molecular techniques, the last two decades have provided deep insights into these diverse and often intricate host-microbe interactions (McFall-Ngai et al., 2013). Insects are the most abundant group of species in terrestrial systems and have evolved symbiotic associations with various microbes (Brownlie & Johnson, 2009;Feldhaar, 2011;Frago et al., 2020). Herbivorous insects in particular host complex communities of bacteria and fungi in their guts that enable them to feed on low-quality and toxin-laden leaf material (Dillon & Dillon, 2004;Hammer & Bowers, 2015). Many insects acquire beneficial symbionts from their surroundings each generation (Kikuchi et al., 2011), while others host more permanent endosymbionts within specialised insect cells, which are transferred vertically from mother to offspring (Douglas, 1998). Plant-sucking insects feed on impoverished diets, and have co-evolved with specialised bacteria that synthesise essential nutrients they cannot acquire directly from the plant (Bennett & Moran, 2015). Over time, this coevolution can lead to genomic erosion resulting in an obligate

Impact of heat stress on the fitness outcomes of symbiotic infection in aphids: a meta-analysis

“…Several mechanistic explanations can be proposed to account for the trait-specific conclusions about the interactive effects of temperature and symbiotic infection on host fitness. First, variability could arise from energetic trade-offs shaping resource allocation between traits (e.g., defense and fecundity), particularly under physiologically constraining conditions such as infection by facultative symbionts and stress-inducing temperatures (15,49). Second, life-history traits frequently differ in their thermal requirement and response to warming (50,51).…”

“…These symbiont-mediated traits might be adaptive under specific ecological contexts like those involving harsh biotic or abiotic stress, but infection by facultative symbionts is also known for inducing fitness costs under more benign environments. Hence, the overall impacts of facultative symbionts on the fitness and adaptive capacity of their hosts can be viewed as a cost-benefit balance tipping in a costly or beneficial state in relation with ecological contingency (13)(14)(15)(16).…”

Frequent Drivers, Occasional Passengers: Signals of Symbiont-Driven Seasonal Adaptation and Hitchhiking in the Pea Aphid, Acyrthosiphon pisum

“…Apart from the obligate nutritional symbionts found in insects with imbalanced diets [ 39 ], most heritable symbionts are thought to be non-essential, or facultative, from the host insect’s perspective—a finding occasionally borne out through lab-based study [ 40 , 41 , 42 , 43 ]. Under certain circumstances, some facultative symbionts may evolve toward obligate associations and ubiquity [ 44 , 45 , 46 , 47 , 48 ].…”

“…Fukatsuia symbionts have been shown to impact all three phenotypes in European pea aphids [ 92 , 93 ]. Beyond these services—which may boost aphid fitness under some field conditions [ 69 ]—costs of these symbionts have been identified [ 43 ]. These vary in their severity, and in the range of ecological conditions under which they have been seen, in both the lab [ 74 , 75 , 90 , 94 , 95 ] and the field [ 69 , 79 , 80 ].…”

Cytotype Affects the Capability of the Whitefly Bemisia tabaci MED Species To Feed and Oviposit on an Unfavorable Host Plant

“…Portiera” can no longer provide. Conversely, other S-symbionts than Hamiltonella rely on the insect host or P- or other S-symbionts for the provision of nutrients (e.g., nonessential amino acids, nucleotides, and nucleosides) ( 49 , 50 ). Therefore, S-symbionts are expected to impact their hosts’ dietary requirements, acting either as sources or sinks of essential metabolites.…”