DOI: 10.5061/dryad.dv41ns1w6
title: Plant-caterpillar interaction matrices of temperate broadleaf forests

description: 1. Assemblages of insect herbivores are structured by plant traits such as
 nutrient content, secondary metabolites, physical traits, and phenology.
 Many of these traits are phylogenetically conserved, implying a decrease
 in trait similarity with increasing phylogenetic distance of the host
 plant taxa. Thus, a metric of phylogenetic distances and relationships can
 be considered a proxy for phylogenetically conserved plant traits and used
 to predict variation in herbivorous insect assemblages among co-occurring
 plant species. 2. Using a Holarctic dataset of exposed-feeding and
 shelter-building caterpillars, we aimed at showing how phylogenetic
 relationships among host plants explain compositional changes and
 characteristics of herbivore assemblages. 3. Our plant–caterpillar network
 data derived from plot-based samplings at three different continents
 included &gt;28,000 individual caterpillar-plant interactions. We
 tested if increasing phylogenetic distance of the host plants leads to a
 decrease in caterpillar assemblage overlap. We further investigated to
 what degree phylogenetic isolation of a host tree species within the local
 community explains abundance, density, richness and mean specialisation of
 its associated caterpillar assemblage. 4. The overlap of caterpillar
 assemblages decreased with increasing phylogenetic distance among the host
 tree species. Phylogenetic isolation of a host plant within the local
 plant community was correlated with lower richness and mean specialisation
 of the associated caterpillar assemblages. Phylogenetic isolation had no
 effect on caterpillar abundance or density. The effects of plant phylogeny
 were consistent across exposed feeding and shelter-building caterpillars.
 5. Our study reveals that distance metrics obtained from host plant
 phylogeny are useful predictors to explain compositional turnover among
 hosts as well as host-specific variations in richness and mean
 specialisation of associated insect herbivore assemblages in temperate
 broadleaf forests. As phylogenetic information of plant communities is
 becoming increasingly available, further large-scale studies are needed to
 investigate to what degree plant phylogeny structures herbivore
 assemblages in other biomes and ecosystems.
description: The sampling was conducted
 in Lanžhot (Czech Republic; 48°42’ N, 16°57’ E; 152 m a.sl.), Toms Brook
 (Virginia, USA; 38°55’ N, 78°25’ W; 220 m a.sl.), and Tomakomai (Hokkaido,
 Japan; 42°43’ N, 141°36’ E; 90 m a.sl.). We employed plot-based sampling
 to investigate insect-plant interactions and the assemblage structure of
 insect herbivores. At each site, we set up two 0.1 ha plots and sampled
 caterpillars from all deciduous trees with a DBH ≥ 5 cm. The sampling was
 carried out during the vegetation seasons between 2013 and 2017, but
 usually finished within two years at a given site (Czech Republic: May,
 2013 – April, 2015; Japan: May, 2014 – July, 2015; USA: April, 2016 –
 August, 2017). Folivorous caterpillars were collected by tree felling
 (USA), by using a canopy crane (Japan), or by using a mobile elevating
 work platform (Czech Republic). To capture seasonal changes in species
 composition, the sampling of con-specific tree individuals was spread
 across the vegetation period. Caterpillars were sampled manually from
 accessible foliage, assigned a morphotype and unique number, reared, and
 subsequently identified. Species identifications were based on external
 morphological characteristics of caterpillars and reared adults, and
 verified by comprehensive DNA barcoding (i.e., sequencing of a 658 bp
 fragment of the COI gene). Adult identification was further aided in many
 cases by genitalia dissections.
description: Caterpillar species sampled in less than three individuals were
 excluded from the matrices in order to eliminate erroneous interaction
 records.