Explaining variation in plant-herbivore associational effects in a tree biodiversity experiment
Cite this dataset
Leonard, Samuel et al. (2023). Explaining variation in plant-herbivore associational effects in a tree biodiversity experiment [Dataset]. Dryad. https://doi.org/10.5061/dryad.9kd51c5pv
Abstract
Within biodiversity-ecosystem function research, a major outstanding question is how herbivory, a critical ecosystem function at the base of the food web, changes along gradients of plant biodiversity. Neighborhood-level associational effects are hypothesized to be a strong driver of biodiversity-herbivory relationships, but we lack a successful framework that explains the wide variation observed in the sign and magnitude of plant-herbivore associational effects, particularly in systems with mainly generalist herbivores. In this study, we combine measurements from a tree biodiversity field experiment with simulation to provide a framework for explaining variation in plant-herbivore associational effects, particularly when herbivores that feed on many different species (e.g., generalists) cause most damage. We show that monoculture herbivory levels of focal species and their neighbors predict the direction and strength of associational effects. We provide evidence that this may be due to a “spillover effect”, in which some insect herbivores attracted to focal individuals ultimately end up feeding on neighboring individuals. With an empirically parameterized simulation, we explain how spatial organization modifies biodiversity-ecosystem function relationships when associational effects operate. We suggest a set of experiments to test the generality of our conceptual framework, to elucidate the underlying mechanisms that produce the patterns we find, and to ultimately increase the predictability of plant-herbivore associational effects. We conclude by discussing how our results might inform pest management in diversified agroecosystems and reforestation sites.
Synthesis
Our results provide a potential framework for explaining why positive and negative plant-herbivore associational effects are often balanced in systems with primarily generalist herbivores and point to a path forward for predicting when increased plant biodiversity will be associated with increased, decreased, or unchanged levels of insect herbivory on individual plant species in such systems.
README: Data for the publication "Explaining variation in plant-herbivore associational effects in a tree biodiversity experiment"
These datasets may be accessed on Dryad at https://doi.org/10.5061/dryad.9kd51c5pv
These datasets were collected in 2016 and 2021, and used in the
manuscript “Explaining variation in plant-herbivore associational
effects in a tree biodiversity experiment”. The datasets contain
information on insect herbivory, leaf traits, and plant size. Methods
for data collection can be found in the manuscript and supporting
information.
The datasets "mydiv_herbivory_may_2021.csv" contains the data on herbivory in May, 2021 due to different functional groups. The columns contain the following information:
- "Plot": the plot number, the mycorrhizal treatment (E for ecto, A for arbuscular, and AE for mixed), and the diversity level
- "tree.species": the binomial nomenclature for each tree species
- "Indiv": the tree individual of a given species within the plot -- either 1, 2, or 3, as there were three replicate tree individuals per species per plot
- "Position": the position within the 12x12 grid of each plot, with the letter giving one coordinate and the number the other
- "Leaf": The leaf on the tree individual; there are 15 leaves per individual
- "Chewer", "Holefeeder", "Miner", "Galler", "Roller", "Sucking", "Skeletonizer", "Rust", "Mildew", "Dasineura-like galls": In each of these columns, we denote the presence (1) or absence (0) of a different kind of leaf damage: leaf chewer, holefeeders, leaf miners, gallers, leaf rollers, leaf suckers, skeletonizers, rust, mildew, or dasinuera-like galls. Further descriptions of different types of herbivore damage are provided in the manuscript.
- "plot_sp_position": simply the plot, tree.species, and position columns pasted together, giving a unique ID for each tree individual
The dataset "mydiv_herbivory_aug_2021.csv" contains the data on herbivory in August, 2021, both due to different functional groups and a quantitative metric per leaf. The columns contain the following information:
- "plot": the plot number
- "species": the binomial nomenclature for each tree species
- "branch": the branch of the tree on which leaves were sampled; leaves were sampled on three branches per tree
- "position": the position within the 12x12 grid of each plot, with the letter giving one coordinate and the number the other
- "Leaf": The leaf on the tree individual; there are 15 leaves per individual
- "chewer", "holefeeder", "miner", "galls", "roller", "skeletonizer", "rust", "mildew": In each of these columns, we denote the presence (1) or absence (0) of a different kind of leaf damage: leaf chewer, holefeeders, leaf miners, gallers, leaf rollers, skeletonizers, rust, or mildewFurther descriptions of different types of herbivore damage are provided in the manuscript.
- "index": the quantitative herbivory index for each leaf (descriptions of categories are provided in the manuscript)
- "my": the mycorrhizal type of the plot
- "div": the diversity level of the plot
- "perc_mean": the median of the range of herbivory values corresponding to the index
- "block": the block of the experiment
The dataset "mini_mydiv_herbivory.csv" contains the data on herbivory in the miniMyDiv experiment in September, 2016. The columns contain the following information:
- "Plot": the plot number/name, the diversity level, and the mycorrhizal treatment
- "species": the binomial nomenclature for each species
- "Indiv": the tree individual for a given species within the plot
- "Leaf": the leaf per individual
- "Chewer", "Holefeeder", "Miner", "Galler", "Roller", "Sucking", "Skeletonizer", "Rust", "Mildew"
The dataset "sem_14.csv" contains the data on leaf traits sampled in July and August, 2021. Only data from diversity levels 1 and 4 are included, as palatability data was only collected at this level. The columns contain the following information:
- "Plot": the plot number
- "species": The binomial nomenclature for each species
- "position": the position of the tree within the plot
- "pubesc.sum": a pubescence index for each leaf, calculated by summing the pubescence on the abaxial and adaxial sides
- "toughness.avg": the average leaf toughness measurement across leaves for a given tree
- "palat_ind": the average palatability index across leaves within a tree
The dataset "sem_nopalat.csv" contains the data on leaf traits sampled in July and August, 2021, but without palatability data. However, it contains leaf trait data for all diversity levels. The columns contain the following information:
- "id": the plot number, species, and position within the plot
- "pubesc.sum": a pubescence index for each leaf, calculated by summing the pubescence on the abaxial and adaxial sides
- "toughness.avg": the average leaf toughness measurement across leaves for a given tree
- "species": the binomial nomenclature for each species
- "plot": the plot number
- "position": the tree individual position within the plot
The dataset "tree_inventory_2021.csv" contains the data on tree size from 2021. The columns contain the following information:
- "plot": the plot number
- "position": the tree individual position within the plot
- "species": the binomial nomenclature for each tree species
- "dbh": diameter at breast height of each individual
- "height": tree height
- "id": a unique id for each tree individual, made up of the plot number, species, and position pasted together
Methods
We include here six datasets. Three (mini_mydiv_herbivory.csv, mydiv_herbivory_may_2021.csv, and mydiv_herbivory_aug_2021.csv) contain leaf-level herbivory data. Columns in this data show the block, plot, diversity of the plot (1, 2, or 4), mycorrhizal characteristics of the plot (A for only arbuscular mycorrhizae, E for only ectomycorrhizae, and AE for both types), tree species, position of the individual within the plot, and branch on the individual. Additional columns show presence/absence of herbivory on each leaf due to leaf chewers, holefeeders, leafminers, gallers, leafrollers, and skeletonizers, as well as the presence of infection (rust or mildew). Additionally, in the August 2021 dataset, an additional column gives a quantitative herbivory index for each leaf, and the "perc_mean" column gives the midpoint of the % leaf area removed category to which that index corresponds to.
sem_14.csv and sem_nopalat.csv contain leaf trait data collected in July and August 2021, averaged at the level of the tree individual (i.e., as the data was used in SEM's described in the manuscript). They show for each tree individual, the plot in which it was located, the species, the position within the plot, the pubescence on a 1 cm diameter disc on each side of the leaf and the sum of these two measurements, the average toughness across multiple leaves. Additionally, sem_14.csv contains data on leaf palatability derived from feeding trials with caterpillars. Since palatability trials were only conducted for leaves from diversity levels 1 and 4, this dataset only contains data from those diversity levels. sem_nopalat.csv omits palatability data, but contains data on the other traits for all three diversity levels.
Finally, tree_inventory_2021.csv contains dbh and height data (along with plot, position, and species identifiers) for trees across the MyDiv experiment in 2021.
Additional methods on data collection can be found in the manuscript main text and supporting information.
Funding
Deutsche Forschungsgemeinschaft
Consejo Nacional de Humanidades, Ciencias y Tecnologías
German Center for Integrative Biodiversity Research
Stanford University
German Academic Exchange Service