Genetic variation in compensatory feeding for dietary dilution in a generalist caterpillar

Kwang Pum Lee

doi:10.1038/s41598-017-07822-4

Abstract

Increasing the rate of food consumption is a common adaptive strategy that allows herbivores to compensate for declines in nutrient concentrations in plant tissues. Herbivores that are better able to compensate for dietary dilution may have selective advantages under nutritionally poor conditions. In order for compensatory feeding to respond to selection, there must be standing heritable variation for this trait. However, empirical data substantiating the adaptive significance and genetic variability of compensatory feeding are rare. By employing a full-sib, split-brood design, this study presents quantitative genetic analyses on the nutrient consumption rates of the generalist caterpillar, Spodoptera exigua, raised on semi-synthetic diets differing in nutrient concentrations. When encountering a diluted diet, caterpillars exhibited a compensatory increase in food consumption rate, but the extent of this increase was not sufficient to fully compensate for dietary dilution. A significant gene-environment interaction for consumption rate indicated that the capacity of caterpillars to compensate for dietary dilution varied across genotypes. The broad-sense heritability of compensatory feeding was 0.51. Caterpillar genotypes with a higher compensatory capacity suffered lower performance losses on the diluted diet than did those with a lower capacity. This study has implications for understanding how herbivores can evolutionarily respond to nutritional challenges.

Highlights

Under natural conditions, herbivores are constantly confronted with suboptimal food conditions due to the deficiency of essential nutrients in plant tissues[1, 2]
Is compensatory feeding really adaptive? The adaptive significance of compensatory feeding lies in the fact that it enables consumers to alleviate the fitness-reducing effects of inferior food quality[7], but empirical studies corroborating the beneficial consequences of compensatory feeding are surprisingly rare[14]
Caterpillars that were restricted to a 50% diluted diet consumed ca. 39.9% more food over days 0–2 than did those restricted to to an undiluted diet (Fig. 1a)

Summary

Introduction

Herbivores are constantly confronted with suboptimal food conditions due to the deficiency of essential nutrients in plant tissues[1, 2]. No study to date has explicitly assessed the genetic variation in compensatory feeding of herbivores in response to nutritionally diluted foods. This study presents a quantitative genetic analysis on the consumption rate of a generalist leaf-chewing caterpillar feeding on semi-synthetic diets with two different nutrient concentrations. The adaptive significance of compensatory feeding lies in the fact that it enables consumers to alleviate the fitness-reducing effects of inferior food quality[7], but empirical studies corroborating the beneficial consequences of compensatory feeding are surprisingly rare[14]. Significance of compensatory feeding, it is necessary to demonstrate whether the capacity of caterpillars to compensate for dietary dilution is genetically correlated with their capacity to reduce the negative consequences of ingesting nutritionally diluted diets

Methods

Results

Discussion

Conclusion