Being a generalist herbivore in a diverse world: how do diets from different grasslands influence food plant selection and fitness of the grasshopper Chorthippus parallelus?

Abstract

1. Generalist insect herbivores occupy a variety of habitats that differ in food plant composition. Dietary mixing has been proposed as a possibility for generalists to overcome nutritional deficiencies of single plant species, but only a few studies have investigated herbivore feeding and fitness for diets that resemble natural scenarios. We studied feeding behaviour, survival, and reproduction of the generalist grasshopper Chorthippus parallelus raised on food plants of four typical habitats. 2. Grasshopper diet consisted of grasses (92.5%), legumes (6.7%) and, in small quantities, other forbs (0.8%). Diet selection differed between the four food plant mixtures, and depended on grasshopper sex and developmental stage. There was no correlation between the relative abundance of plant species in the field and the fraction of these species in the grasshopper diet. 3. Grasshoppers survived on average for 40.4 ± 1.0 days before maturity, grew 106.8 mg until maturity moult, and females laid 4.1 ± 0.4 egg pods, each of which contained 8.5 ± 0.4 eggs. However, despite the differences in feeding behaviour, grasshopper fitness was the same in all of the four food plant mixtures. While the digestibility of ingested food was similar in the four different treatments, indices indicated differences in the conversion efficiency to body mass. 4. Our results show that C. parallelus is a plastic feeder with no fixed preferences in diet composition. The results emphasise that generalist herbivores can counteract putative quality deficiencies of single food plants by selective dietary mixing.

The spatial and temporal distributions of arthropods in forest canopies: uniting disparate patterns with hypotheses for specialisation

“…Furthermore, polyphagy will be favoured by migratory species, since different suites of host plants are likely to be encountered in different locations (Michaud, 1990). Diet-mixing is also predicted under the physiological-efficiency hypothesis to reduce the build up of defensive chemicals and counteract nutritional deficiencies that may arise from single-host diets (Held & Potter, 2004;Franzke et al, 2010;Karban et al, 2010). However, DNA barcoding has shown that some widespread, generalist species are actually complexes of multiple closely related host-specific species (Hebert et al, 2004;Janzen et al, 2009Janzen et al, , 2012Valentini, Pompanon & Taberlet, 2009; but see Hulcr et al, 2007a).…”

Discrimination of grasshopper (Orthoptera: Acrididae) diet and niche overlap using next‐generation sequencing of gut contents

“…Changes in diet across a species’ range have been observed in other grasshopper species (Franzke et al. 2010). Additionally, DNA analysis of diet cannot reflect diet over a large temporal scale as it is limited by the transit time of food through the digestive tract of grasshoppers – estimated at 6 h (Chapco and Kelln 1994).…”

Proteome data on the microbial microbiome of grasshopper feces

“…The meadow was dominated by grasses, namely Poa pratensis, Dactylis glomerata , Festuca pratensis , and Bromus sterilis , which are all potential food plants for the generalist herbivores in grasslands [1], [2], [3], [4]. Three days before the start of the experiment, we caught female and male grasshoppers with sweep nets and kept them separately in cages with a mixed grass diet from the meadow until the start of the experiment.…”