Insect and plant traits drive local and landscape effects on herbivory in grassland fragments

Abstract

Herbivory is one of the most important antagonistic insect–plant interactions and can be influenced by factors at local and landscape scales. Landscape fragmentation may reduce herbivory directly (i.e., decreasing abundance and species richness of herbivores), but also indirectly increase herbivory (i.e., releasing herbivores from top‐down control). At a local scale, reduced plant diversity may enhance herbivory through lessened associated resistance, while resource availability (i.e., higher vegetation height and cover) may promote herbivory. Few studies have simultaneously considered the influence of local and landscape variables on insect herbivory. We evaluate effects of landscape (fragment size, connectivity, and arable land percentage) and local factors (plant cover and height and plant species richness) on insect herbivory in fragmented calcareous grasslands. Further, we ask whether these effects depend on feeding traits of herbivores (chewers vs. suckers) and habitat specialization of plants (specialists vs. generalists). Results show that herbivory was best explained by models including variables at both local and landscape scales. However, local factors were more important than landscape variables. Herbivory was in all cases positively related to height of herbs (i.e., taller and more heterogeneous food resources), whereas the effect of plant species richness varied with feeding traits of herbivores. Herbivory by chewers, which are commonly more generalist feeders, was negatively affected by plant species richness, supporting the idea of associated plant resistance. In contrast, herbivory by suckers, which tend to be more specialized, increased with plant richness. Although there was little influence of landscape scale, herbivory on specialist plants was significantly higher in smaller grasslands probably as a consequence of herbivore release from natural enemies. Functional redundancy among herbivore species would allow to maintain overall herbivory in fragmented calcareous grasslands. This study highlights the need to consider different herbivore and plant traits for a better understanding of herbivory responses to local and landscape factors.

Tree diversity drives associational resistance to herbivory at both forest edge and interior

“…well identified herbivore species (e.g.,Plath, Dorn, Riedel, Barriois, & Mody, 2012;Damien et al, 2016;Muiruri & Koricheva, 2016). Yet, the leaves may have accumulated mines made by several species, showing the same pattern of response to tree diversity as the diversity of herbivore guilds.Our results provide no supporting evidence to the effect of tree location at forest edge or interior on herbivore-plant interactions.This result confirms those recently found byvan Schrojenstein Lantman et al (2018) andRossetti, Verena, Videla, Tscharntke, and Batary (2019), but contradictsWirth et al (2008) andMaguire et al (2016) who showed that tree location can affect herbivory patterns. The only significant effect of tree diversity was observed on leaf miners in our study.…”

Agroecological transition increases arthropod diversity and decreases herbivore abundance on field margins

“…Maximum vegetation height (VH) did not show any effect on any of these groups. This is not consistent with other studies where this structural feature was relevant for herbivores (Rossetti et al, 2019). In our system, this might be explained by the dominance of a tall grass invasive species (Sorghum halepense) on some edges.…”

Characteristics of Microbial Communities of Pachygrontha antennata (Hemiptera: Pachygronthidae) in Relation to Habitat Variables

“…Land use data were obtained from the Ministry of Environment, Korea. Land use data were extracted for a 500 m radius of each collection site [16,32,33] using GIS software (version 10.1, ArcGIS, Redlands, CA, United States), and these data were used to calculate the proportion (%) of each land use. To avoid issues with GIS, distances that covered the largest area of a particular region were used, and the GPS coordinates were used as the site of origin to minimize potential errors caused by the GIS process.…”