Dietary differences between grasshoppers are associated with life history tradeoffs in an alpine meadow

Abstract

Dietary differences are often observed among generalist herbivores co-occurring in the same community. However, the factors underlying the differences remain poorly understood. In the context of insect herbivores, we hypothesized that interspecific dietary differences are associated with life history traits. Specifically, we hypothesized that the size of wings as well as gender participate in defining dietary preferences, that is, long-winged species and males will tend to forage on plants with high C/N to maximize dispersal and mating, whereas short-winged species and females will forage on N-rich plants to maximize egg production. We tested this hypothesis by examining the diets of the males and females of three long-winged and two short-winged grasshopper species in an alpine meadow. The dietary composition and relative abundance of each species were determined using DNA meta-barcoding. The data showed that the consumed plant species were similar among all of the grasshopper species and between the males and females. However, quantitative differences in the diets were significant between the long-winged and shortwinged guilds and between the males and females of each species. Consistent with the hypothesis, (1) the long-winged species fed more on monocots with high C/N, whereas the short-winged species fed more on legumes with high N contents, (2) for each short-winged species the males fed more on monocots with high C/N compared to the females, and (3) across all grasshopper species, egg numbers were positively associated with the weighted dietary N. These data indicate that the dietary preferences of these generalist grasshoppers are associated with life history tradeoffs.

Insect root feeders incur negative density‐dependent damage across plant species in an alpine meadow

“…Fortunately, DNA metabarcoding provides an effective and accurate method for identifying the plant species (and their abundance) that are included in the diet of root feeders under natural conditions (Soininen et al, 2009). The reliability of this molecular method has been confirmed in the case of grasshoppers (Lan et al, 2021) and leaf roller beetles (Kajtoch et al, 2015). This study, as well as others, has shown that DNA metabarcoding can track feeding interactions that are not observable by means of traditional methods (Clare et al, 2014; Kress et al, 2015; Symondson, 2002; Valentini et al, 2009).…”

“…The primers ITS2‐S2F and ITS2‐S3R (Chen et al, 2010) have been verified to quantify the intestinal plant species composition of grasshopper species by high‐throughput second‐generation sequencing (Lan et al, 2021), and the primers have a discriminatory power higher than that of plastid markers (Chen et al, 2010; Li, Gao, et al, 2011). In the case of root feeders, the DNA region used should be short enough to amplify degraded DNA (Staudacher et al, 2011).…”

“…Tissue samples were collected from an individual of each plant species and preserved in plastic bags containing silica gel. Details on the DNA extraction procedure are provided by Lan et al (2021). The sequences were then organized into plant barcode database, which included ITS2 sequences from our local collection of 266 plant specimens representing 130 dominant plant species that might have been used by the insect herbivores in our study site (Lan et al, 2021).…”

Availability of mates and food influence the plasticity in strategies mediating life‐history tradeoffs in an insect

“…The nutritional quality of food also plays an important role in mediating the flight-reproduction tradeoff because a high carbohydrate diet can eliminate the reproductive advantage of flightlessness in G. lineaticeps (Treidel et al 2021) while protein and carbohydrate effects on ovary versus flight muscle mass vary between flight-capable and -incapable G. firmus (Clark et al 2015). The nutrient content of food mediates life-history tradeoffs in other insects, as well (Gutiérrez et al 2020, Lan et al 2021) -thus, both food availability and quality may play important roles in driving plasticity in life-history strategies.…”

Moderate Grazing Promotes Arthropod Species Diversity in an Alpine Meadow

“…Moreover, the diversity of plant functional types (in the moderate grazing treatment) may facilitate the survival of generalist herbivore species requiring more than one functional type of plants [ 62 ]. For example, some grasshopper species are more generalized in feeding on both grass and forb species than some other grasshopper species [ 63 ]. In addition, grazing may directly facilitate herbivore species diversity.…”