Foliar Phenolics are Differently Associated with Epirrita autumnata Growth and Immunocompetence

Abstract

The quality of available food may affect insect herbivores directly (via growth and survivorship) and/or indirectly (by modifying insect vulnerability to parasitoids and pathogens). We examined the relationship between different phenolic compounds, belonging to various phenolic groups, in Betula pubescens spp. czerepanovii (mountain birch) foliage and the larval performance of the geometrid Epirrita autumnata (autumnal moth). Direct effects on insect performance were described by pupal weight, developmental rate, and survivorship; indirect effects were described by the encapsulation rate of an implant inserted into the insect hemocoel, a commonly used way to describe insect immune defense. We found profound differences in the effects of different phenolic categories: several individual hydrolyzable tannins were associated positively with larval performance but negatively with level of immune defense, whereas flavonoid glycosides were inversely related to larval survival but showed no association with the larvae immune defense.

Complex effects of parasitoids on pharmacophagy and diet choice of a polyphagous caterpillar

“…It is one of the most effective defenses that insects have against parasitic wasps and flies (Godfray 1994;Beckage 2008;Smilanich et al 2009b). Several studies have investigated the effects of host plant chemistry on immune function in herbivorous insects (Benrey and Denno 1997;Turlings and Benrey 1998;Hunter 2003;Smilanich et al 2009a), showing that the effects can be positive, negative, or neutral (Ojala et al 2005;Kapari et al 2006;Haviola et al 2007;Klemola et al 2007Klemola et al , 2008Lee et al 2008;Smilanich et al 2009a;Bukovinszky et al 2009). Nutrients (e.g., protein) can enhance encapsulation and lysozyme-like antibacterial activity, while other immune system components like phenoloxidase activity may not be affected (Lee et al 2006(Lee et al , 2008Povey et al 2009;Srygley et al 2009).…”

“…Nutrients (e.g., protein) can enhance encapsulation and lysozyme-like antibacterial activity, while other immune system components like phenoloxidase activity may not be affected (Lee et al 2006(Lee et al , 2008Povey et al 2009;Srygley et al 2009). Ingestion of certain plant secondary metabolites (e.g., iridoid glycosides) can diminish the immune response by directly interfering with melanization (Smilanich et al 2009a), whereas other metabolites (e.g., hydrolyzable tannins) may act indirectly on immunity via reductions in herbivore performance (i.e., declines in host quality from the perspective of the parasitoid) (Haviola et al 2007;Yang et al 2008). Alternatively, antioxidant activity associated with carotenoids, phenolics, and synthetic chemicals can enhance insect immunity by putatively reducing harmful oxygen species (Ojala et al 2005;Buyukguzel 2009).…”

Immune defence strategies of generalist and specialist insect herbivores

“…However, a narrow diet breadth may yield benefits seen only under natural conditions, taking the effects of nutrients and secondary metabolites of the host plant additionally into account. Studies on the relationship between insect immunity and diet breadth have revealed that variation in host plant quality can alter the immune defence response [54], and that secondary metabolites can decrease the immunocompetence and increase parasitism rates in insects [55][56][57]. By contrast, a recent study demonstrated that the immune system response of a generalist did not vary when fed on three different plant species, suggesting that feeding on various host plants of different nutritional qualities and secondary metabolite content has no detrimental effect on immune system response in this case [58].…”

Microbial Root Mutualists Affect the Predators and Pathogens of Herbivores above Ground: Mechanisms, Magnitudes, and Missing Links

“…High concentrations of plant secondary metabolites tend to reduce immune defenses, probably because of their negative effects on insect growth rate and reduced allocation to immune functions. For example, hydrolysable tannins in quaking aspen (Populus tremuloides) correlate negatively with immune defense in the autumnal moth Epirrita autumnata (Haviola et al, 2007), and high iridoid glycoside concentrations in P. lanceolata compromise immune responses in the common buckeye caterpillar Junonia coenia (Smilanich et al, 2009). Lower immune defense can lead to higher performance of parasitoids (Reudler et al, 2011;Kos et al, 2012).…”