Large numbers of fruit fly larvae can overcome extreme nutritional imbalances of their food

Carlos Pascacio-Villafán, Nicoletta Righini, David Nestel, Andrea Birke, Larissa Guillén, Martín Aluja

This is a plain language summary of a Functional Ecology research article which is published here.

Anastrepha ludens female ovipositing in grapefruit (left panel), and an experimental diet with a high larval density treatment (right panel). Photo credit: Erick Enciso and Carlos Pascacio-Villafán.

The quality of the diet consumed during early stages of life, and the presence and abundance of individuals of the same species feeding on the same food resource, are critical factors that affect the development and life history of many animal species including insects.  We experimentally examined how multiple immature and adult traits of the Mexican fruit fly, Anastrepha ludens, a fruit fly pest whose larvae can feed on many types of wild and cultivated fruit and live in groups of varying sizes in temporary and nutritionally variable environments, vary depending on the macronutrient content of its larval diet across extreme levels of larval densities in the same food resource.  We analysed morphological and life history traits of flies, such as body weight and development time respectively, and used the survival of flies from the immature to the adult stages (that is, from larva to pupa and larva to adult) as a measure of success.  We analysed several macronutrient x larval density scenarios and found positive effects on multiple traits and performance when protein and carbohydrate content in the diet increased, but negative effects when carbohydrates were extremely high.  Higher body weight and survival to adulthood were associated with low protein and carbohydrate content, high protein ratios, and low larval densities.  Our results support the hypothesis that extreme macronutrient imbalances (for example very high protein or sugar content) in the diet of frugivorous insects are a barrier for larval development, which can be overcome by cooperative feeding behaviour of large numbers of larvae that can collectively reduce the quantities of deleterious nutrient surpluses in the food.  This study helps to understand the nutritional and population factors that affect the development of pest fruit flies, and that can potentially limit their geographical range and host expansion.