Larval and/or Adult Exposure to Intraguild Predator <i>Harmonia axyridis</i> Alters Reproductive Allocation Decisions and Offspring Growth in <i>Menochilus sexmaculatus</i>.

Abstract

Maternal effects can reduce offspring susceptibility to predators by altering resource allocation to young and reproducing larger offspring. While the perception of predation risk can vary according to a prey's life stage, it is unclear whether maternally experienced intraguild predation (IGP) risk during different life stages influences the maternal effects of predatory insects. We investigated the influence of exposure to intraguild predators (<i>Harmonia axyridis</i> (Pallas) (Coleoptera: Coccinellidae)) during the larval and/or adult stages on reproductive decisions and offspring growth in <i>Menochilus sexmaculatus</i> (Fabricius). Independent of the life stage, when <i>M. sexmaculatus</i> females experienced IGP risk, their body weight and fecundity decreased, but the proportion of trophic eggs produced increased. However, egg mass, egg clutch number, and egg clutch size were not influenced by the treatment. Next, when offspring encountered <i>H. axyridis</i>, mothers experiencing IGP risk during the larval and/or adult stages could increase their offspring's weight. Moreover, offspring in IGP environments reached a similar size as those with no-IGP environments when mothers experienced IGP risk during the larval and/or adult stages. Overall, <i>M. sexmaculatus</i> larval and/or adult exposure to IGP risk had no influence on egg size, but increased offspring body size when faced with <i>H. axyridis</i>. Additionally, mothers experiencing IGP risk during different life stages showed increased production of trophic eggs. Because IGP is frequently observed on <i>M. sexmaculatus</i> and favours relatively larger individuals, different stages of <i>M. sexmaculatus</i> express threat-sensitively to IGP risk; inducing maternal effects can be an adaptive survival strategy to defend against <i>H. axyridis</i>.