Data from: Forest defoliation by an invasive outbreak insect: Catastrophic consequences for a charismatic mega moth
Data files
Apr 21, 2025 version files 76.91 KB
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analysis_code.R
12.80 KB
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analysis_code.Rmd
10.87 KB
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forest_phytochemistry_data.csv
37.76 KB
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polyphemus_bioassay_data.csv
11.11 KB
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README.md
4.36 KB
Abstract
Earth is now experiencing declines in insect abundance and diversity unparalleled in human history. The drivers underlying those declines are many, complex, and incompletely known. Here, using a natural experiment, we report the first test of the hypothesis that forest defoliation by an invasive outbreak insect compromises the fitness of a native insect via damage-induced increases in toxicity of the forest canopy. We demonstrate that defoliation by the invasive spongy moth (Lymantria dispar) elicits an average 8.4-fold increase in foliar defense expression among aspen (Populus tremuloides) genotypes. In turn, elevated defense dramatically reduces survivorship, feeding, and growth of a charismatic mega moth (Anthereae polyphemus). This work suggests that changes to the phytochemical landscape of forests, mediated by invasive outbreak insects, are likely to negatively impact native insects, with potential repercussions for community diversity and ecosystem function across expansive scales.
General description data from invasive species defoliation study
This file describes the data files associated with the manuscript Forest defoliation by an invasive outbreak insect: catastrophic consequences for a charismatic mega moth. This project investigated downstream effects of an invasive outbreak species (L. dispar) on chemical composition of a host plant (aspen) to a charismatic native species(Anthereae polyphemus). We analysed phytochemical defense compounds (salicinoid phenolic glycosides, SPGs) between undefoliated forest throughout the year in which the outbreak took place. We assessed polyphemus larval performance via targeted feeding bioassays, incorporating leaves from the previously undefoliated and defoliated aspen forests.
Forest phytochemistry data
The file entitled forest_phytochemistry_data.csv contains data on aspen SPG (salicinoid phenolic glycoside) levels collected over multiple years (2020-2021) from two experimental forests. Each row represents observations for a single tree.
Variable (column) descriptions are as follows:
- year: calendar year during which the tree was sampled
- forest: the experimental forest in which the tree resides. "UND" indicates the forest that was not subject to
the L. dispar outbreak (undefoliated) and "DFL" indicates the forest that was defoliated. - source: a data clustering identifier ("A", "B", "C", or "D") used to filter the data for some analysis.
- collection_period: the calendar period during which leaves were collected from trees for chemical analysis.
- genet: the unique identifier of the tree's genotype.
- tree_ID: the unique identifier of the individual tree.
- Scort_pct, Tcin_pct, Scin_pct, Tdin_pct, and SPG_pct: the measured concentration, as a percent
of dry leaf mass, of the salicinoids salicortin, tremulacin, salicortin, tremuloidin, and their sum. - outbreak: indicates whether the trees were measured before ("pre") or after ("post") the outbreak of L. dispar.
Polyphemus bioassay data
The file entitled polyphemus_bioassay_data.csv contains data from the Polyphemus feeding trials, in tabular form.
Each row represents observations taken from a single third instar (L3) larva. Missing data, caused by larval mortality are represented by 'NA'. The columns are grouped such that columns 1-3 provide tree information, 4-8 provide foliar chemistry (salicinoid) data, 9-10 provide larva information, and 11-17 provide larval performance data.
More detailed variable (column) descriptions are as follows:
- forest: the experimental forest from which bioassay leaves were collected. "UND" indicates the forest that was
not subject to the L. dispar outbreak (undefoliated) and "DFL" indicates the forest that was defoliated. - genet: the unique genotype identifier of the tree from which bioassay leaves were collected.
- tree_ID: the unique tree identifier from which bioassay leaves were collected.
- Scort_pct, Tcin_pct, Scin_pct, Tdin_pct, and SPG_pct: the measured concentration, as a percentage
dried leaf mass, of salicorin, tremulacin, salicin, tremuloidin, and total salicinoid phenolic glycocides (i.e., sum of
preceding four SPGs). - larval_ID: the unique identifier for an individual bioassay larva.
- larval_rep: larval replicate (1 or 2). For each tree within a genotype, two replicate larvae were included in
the bioassays. - consumption_mg: the amount of dry biomass, in milligrams, consumed by a larva during the bioassay.
- biomass_gained_mg: the amount of dry biomass, in milligrams, gained by a larva during the bioassay.
- RGR: relative growth rate, in dry milligrams per milligram per day, of a larva during the bioassay.
- RCR: relative consumption rate, in dry milligrams per milligram per day, of a larva during the bioassay.
- instar_duration_d: total number of days that the larva remained in the third larval stadium.
- larva_survived: indication of whether ("yes") or not ("no") the larva survived the bioassay.
Analysis
The documents analysis.Rmd and analysis.R contain R code needed to reproduce the statistical analyses conducted in the manuscript.
- Lindroth, Richard L.; Zierden, Mark R.; Morrow, Clay J.; Fernandez, Patricia C. (2024). Forest defoliation by an invasive outbreak insect: Catastrophic consequences for a charismatic mega moth. Ecology and Evolution. https://doi.org/10.1002/ece3.70046