Plant-Induced Transgenerational Plasticity Affecting Performance but Not Preference in a Polyphagous Moth

Abstract

Environmental variation experienced by a single genotype can induce phenotypic plasticity in various traits, such as behavioural, physiological and developmental characteristics. It can occur within the lifetime of an individual through within-generation phenotypic plasticity (WGP) or vertically across generations through transgenerational phenotypic plasticity (TGP). However, knowledge about TGP and the co-occurrence of WGP and TGP is still limited. In insect host-plant selection, the ability to alter phenotypic traits through WGP is well documented while the importance of TGP and the possible co-occurrence between the two is largely unknown. Host-plant selection of both larvae and adults of the polyphagous moth Spodoptera littoralis can be modified by previous experience through WGP. Thus, the aim of this study was to investigate if parental host-plant experience can influence host-plant choice behaviour and performance of S. littoralis offspring through TGP. For this, we tested effects of rearing parents on different host plants on the offspring's first instar larval migration and host plant choice, larval development and adult oviposition. A transgenerational effect on larval development was found, with increased pupal weight on a matching host-plant diet to that of the parent, when larvae were reared on cotton (good larval host plant) while no such effect was found on maize (poor larval host plant). These findings indicate that TGP of S. littoralis progeny development traits may only occur under favourable conditions. Parental diet did not affect larval host plant choice or migration. Furthermore, no effect of parental diet was found on offspring oviposition behaviour, indicating that adult female host-plant selection is governed by innate preference hierarchy and WGP, rather than TGP. Thus, parental diet may influence offspring performance but not behaviour, indicating that WGP is most important for host-plant selection behaviours in S. littoralis, but TGP can affect progeny development. If so, the importance of different types of plasticity may vary among traits of S. littoralis associated with host plant utilisation.

What should a poor mother do? Influence of host plant quality on oviposition strategy and behavior in a polyphagous moth

“…maternal effects, where non-genetic components, such as egg nutrients, are transferred from the mother to her offspring to improve their fitness (Bernardo 1996). However, as the results in our current paper indicate that females do not alter egg size depending on larval host plant species, we suggest that egg size in itself does not explain the mechanism behind the transgenerational effects previously found in S. littoralis (Rösvik et al 2020). Indeed, egg size may not be the only parameter for estimating egg investment and egg quality as the yolk protein content could be unrelated to egg size (Diss et al 1996).…”

“…There may also be more complex relationships between egg quantity and egg quality in insects than a simple trade off (Fischer et al 2003). Rösvik et al (2020) recently showed indications of transgenerational plasticity on offspring performance in S. littoralis depending on parental host plant species during the larval stage.…”

“…) indicating important effects of plant species on individuals' condition. The larval host plant species of parents furthermore have transgenerational effects on their offspring performance (Rösvik et al 2020). Host plant induced plasticity does, however, not only occur on performance but also on preference in S. littoralis.…”

Insects Provide Unique Systems to Investigate How Early-Life Experience Alters the Brain and Behavior

“…Many fundamental questions that are common to both insects and vertebrates remain to be resolved, for example, how the brain integrates early-life experience across multiple levels of organization, and whether specific mechanisms like DNA methylation universally predict long term behavioral impacts. Moreover, it remains unclear how developmental experiences are integrated with other sources of information (e.g., genetic variation, parental transgenerational effects) that also influence behavior (Dall et al, 2015;Stamps and Frankenhuis, 2016;Stein et al, 2018;Rösvik et al, 2020), and whether these outcomes can be modified by additional information later in life. Though these sources of complexity apply to both insect and vertebrate species, certain characteristics of insects, like their relatively short lifespans, may alter the ecological selection pressures that shape information integration.…”

The effects of host plant species and larval density on immune function in the polyphagous moth Spodoptera littoralis

“…Spodoptera littoralis feeds on more than 80 different plant species from over 40 different families (CABI, 2019), and the host range thus spans over plants which may be very different in terms of nutrient content and chemical defenses. This species has been shown to be very plastic in terms of host plant preference and performance (Anderson et al, 2013;Lhomme et al, 2018;Proffit et al, 2015;Rösvik et al, 2020;Roy et al, 2016;Thöming et al, 2013), where larval development, fecundity, and mating propensity differ depending on which host plant species they feed on (Rösvik et al, 2020;Karlsson Green et al, 2021). Furthermore, parasitoid success on S. littoralis could differ depending on host plant species, which may result from a combination between increased larval immune defense and variation in parasitoid search behavior depending on plant species (Sadek et al, 2010).…”