Plant species, mycorrhiza, and aphid age influence the performance and behaviour of a generalist

Abstract

1. Life‐history traits of herbivores are shaped by the combination of various extrinsic and intrinsic variables. However, studies investigating the impact of both variables on insect behavioural phenotypes are rare, and research including the modulation of host plant quality by arbuscular mycorrhiza (AM) (extrinsic variable) and the herbivore developmental stage (intrinsic variable) on aphid behaviour is lacking. 2. To study the influences of extrinsic and intrinsic variables on aphid performance and behaviour, individuals of the generalist aphid pest Myzus persicae (Sulzer) were reared on Plantago lanceolata and Poa annua plants that were either non‐mycorrhized (NM) or mycorrhized (AM). Aphid performance was monitored over 2 weeks. Behavioural traits of nymphs were recorded twice during development after removing individuals from their feeding sites and placing them in an unknown environment (‘open field’), causing disturbance. Plant quality was determined by measuring the water content and leaf mass per area (LMA). 3. Differences in body mass of nymphs at day 6 dependent on plant species and treatment were compensated by the individuals within 4 days. Behavioural traits, considered as activity and exploration, were affected by the interaction between extrinsic and intrinsic variables (activity and exploration) and changed over ontogeny (activity). Independent of AM, a lower water content and LMA were recorded in P. annua leaves. 4. Overall, this study demonstrates that extrinsic and intrinsic variables need to be considered in combination and behavioural traits should be studied repeatedly during insect ontogeny to understand the complexity of microbe‐modulated plant–herbivore interactions.

Impacts of aphid herbivory on mycorrhizal growth responses across three cultivars of wheat

“…These differences could be driven by the variable rates at which AM fungi colonise plant roots (Hart & Reader, 2002), as the stage of AM colonisation can determine how mycorrhizal fungi impact aphid development (Tomczak & Müller, 2017), perhaps due to the triggering of different phytohormonal pathways at different phases of root infection (Cameron et al, 2013). In studying the effect of mycorrhizal colonisation on aphid numbers alone, it is conceivable that fungal‐mediated effects on other aspects of aphid performance were missed, such as relative growth rate (Tomczak & Müller, 2017, 2018), survivorship (Volpe et al, 2018) and feeding behaviour (Simon et al, 2017). Over longer time periods—such as a full growing season—or in non‐crop systems, these subtle changes may ultimately impact pest numbers and thus herbivore pressure, meaning these traits should be considered in subsequent research into this economically important yet poorly studied tri‐partite system.…”

High levels of arbuscular mycorrhizal fungus colonization on Medicago truncatula reduces plant suitability as a host for pea aphids (Acyrthosiphon pisum)

“…So far, a few aphid behavioral traits (activity, exploration, and boldness) were examined on two plant species that were either noncolonized or colonized by AM fungi (Tomczak et al, 2016). It was shown recently that extrinsic (host plant quality modulated by AM symbiosis) and intrinsic (aphid age) variables can impact aphid performance and behavior (activity and exploration) differently (Tomczak & Müller, 2018). Aphids are known to ingest all compounds present in sieve elements such as carbohydrates, amino acids, proteins, water, and others.…”