Transgenerational effects: nutrition, immunity and infection dynamics in Plodia interpunctella.

Abstract

Phenotype can be shaped by transgenerational effects from parental and even grandparental environments. Parental resource allocation strategies can alter offspring condition to increase fitness. Alternatively, environmental influences such as stress, pollution, or pesticides, can be transmitted as non-adaptive “developmental noise”. This thesis explores the roles that nutrition and infection play as transmitted effects to offspring, using the Indian meal moth Plodia interpunctella as a model host. Parents acquire more resources to provision offspring with through their diet. However, interactions with offspring environment often go unexamined due to the complex nature of these factorial studies. Using good and poor diet qualities, I demonstrate the relative importance of parental and offspring environments and how this changes for offspring disease resistance, weight and longevity. I find that parental effects are present but are modest in comparison to the effects of the offspring’s own environment. I then develop a synthetic artificial diet to examine which macronutrients (such as protein and carbohydrate) within parental diet influence offspring phenotype. These diets allowed both the total nutritional content to be diluted, and the ratio of protein and carbohydrate to change. I find that offspring are relatively robust to extreme changes in parental dietary macronutrient content, which possibly explains the success of Plodia interpunctella as a widespread pest species. Vertical transmission of upregulated immune function has recently been demonstrated in insects, which is reliant on parental exposure but functions without an obvious acquired transmitted cue. To date, experiments have been conducted using single infections under laboratory conditions. However, this study shows that in a more ecologically realistic scenario involving multiple infections and resource limitation, maternal pathogen exposure results in environmentally-contingent decreases in offspring survival in response to infection. Transgenerational immune priming may not as common as previously thought, and any benefits accrued to offspring should be viewed within an inclusive framework that includes potential costs to the parents.