Unapparent trees: escaping enemies in time by being discreet, unpredictable and inaccessible
Data files
May 21, 2025 version files 98.40 KB
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Caterpillar-Data-Unapparent-trees.csv
47.72 KB
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Pupaation-data-Unapparent-trees.csv
29.42 KB
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R-code-Unapparent-trees.R
14.45 KB
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README.md
6.82 KB
Abstract
For half a century, biologists considered trees as particularly apparent to their enemies. But why then do some trees escape herbivorous enemies by bursting buds either too early or too late, leading to phenological mismatch? We hypothesize that such mismatches occur on trees that are unapparent in time—those that burst buds “discreetly” (slowly) and unpredictably (inconsistently across years), and are difficult to access (host trees among non-hosts). We studied herbivores on oaks in Western France. We for the first-time characterized phenology matching of an entire guild of herbivores, early spring ectophagous caterpillars (45 species). We examined whether, on a given date, caterpillars have a large body size and impact (herbivory), and whether this size or impact is largest on trees that burst buds earliest. Furthermore, we distinguished the contributions of within-guild sorting of species and within-population selection of individuals to phenology matching, we investigated whether present phenology matching was determined during past generations by testing if caterpillars from trees with early-maturing foliage pupate early, even when transferred into a common garden. We found that caterpillar size and herbivory impact in the field and pupation date in the lab generally matched leaf phenology in the field. Such phenology matching was consistently observed at the intraspecific level but was less evident at the interspecific level. Together this indicates that phenology matching is mainly driven by past within-population selection rather than present, within-guild sorting. Furthermore, herbivores size and impact were most constrained by late bursting of host trees if these trees burst buds slowly and unpredictably and are difficult to access. We suggest that, during the assembly of early-spring herbivore guilds, trees can best constrain development of herbivore populations by late budburst and remaining unapparent in time—bursting buds discreetly, unpredictably across years, or in inaccessible neighbourhoods.
Dataset DOI: 10.5061/dryad.nzs7h452t
Description of the data and file structure
The data are also given in the Supplementary document, and are described there.
Files and variables
File: Caterpillar-Data-Unapparent-trees.csv
Description: This file contains data on caterpillars, including their length measured within two days of field collection. It also includes characteristics of the host trees from which the caterpillars were collected, such as budburst timing, budburst speed, within-crown heterogeneity of budburst, and phylogenetic and spatial distances from neighbouring trees. Entries marked as "NA" indicate that data were not available for those specific cases.
Variables
- Row.number: Unique row number
- Year: Year of sampling i.e. 2010 or 2011 or 2019
- Tree: Unique identification number of the trees
- Budburst.DOY: Day of the year when a tree reached its mid-point of budburst
- Mean.budbusrt: Mean of Budburst.DOY of all the trees in a given year
- Relative.budburst: In a given year, the difference (in days) between a tree’s budburst date (Budburst.DOY) and the mean budburst date all the trees (Mean.budburst).
- Budburst.speed: The rate at which a tree completes budburst, measured as the average daily increase in budburst score from the onset of budburst until completion (see Methods for details). The unit is budburst score per day.
- Budburst.heterogeneity: The standard deviation of budburst scores measured across 20 individual buds on a single tree.
- Budburst.consistency: The consistency of a tree’s budburst timing across years, reflecting whether it consistently buds earlier or later relative to others, or shows variability (e.g., early in one year but average in another). This was quantified as the standard deviation of the tree’s Relative.budburst values across years (see Methods for details).
- Phy.Iso: Phylogenetic isolation of a tree, defined as the average phylogenetic distance (in millions of years) between the focal tree and all neighboring trees with which it shares direct crown contact (see Supplementary Material for details)
- Dist2Oak: The spatial distance (in meters) from the focal oak tree to its nearest conspecific neighbor.
- Leaf.advancement: A measure of leaf maturation in mid-June, indicating the development level of defensive chemicals (e.g., flavonols, anthocyanins) and physical traits (e.g., toughness, thickness) at this stage (see Methods for details). As a relative measure, this variable is unitless.
- Caterpillar.abundance: Number of caterpillar present per leaf of a tree in a given year
- Herbivory.rate: Proportion of leaf area consumed by ectophagous caterpillars
- Caterpillar.ID: Unique identification number of each caterpillar in a given year
- Caterpillar.size(mm): Length of caterpillars in milimeters (measured within two days after collection from the field)
- Caterpillar.species: Species identity of each caterpillars
- Caterpillar.species.mean.timing: The average relative budburst timing (in days) of all host trees used by caterpillars of a specific species within a given year (see Methods for details).
- Within.caterpillar.species.timing: For an individual caterpillar in a given year, the deviation (in days) of its host tree’s budburst timing from the species-specific mean budburst timing (i.e., Caterpillar.species.mean.timing; see Methods for details).
File: Pupaation-data-Unapparent-trees.csv
Description: This file contains data on the timing of pupation, specifically the day in 2019 when caterpillars collected from the field pupated under laboratory conditions. It also includes characteristics of the host trees from which the caterpillars were collected, such as leaf development stage, budburst timing, budburst speed, within-crown budburst heterogeneity, and phylogenetic and spatial distances to neighboring trees. Entries marked as "NA" indicate that data were not available for those specific cases.
Variables
- Cat ID: Unique identification number of each caterpillar in 2019
- Tree: Unique identification number of the trees
- Pupation Date: Date when the caterpillar pupated (format DD/MM/YYYY)
- Pupation DOY: Day of year when the caterpillar pupated
- Leaf advancement: A measure of leaf maturation in mid-June, indicating the development level of defensive chemicals (e.g., flavonols, anthocyanins) and physical traits (e.g., toughness, thickness) at this stage (see Methods for details). As a relative measure, this variable is unitless.
- Caterpillar.species: Species identity of each caterpillars
- Caterpillar.species.mean.leaf.advancement: The average 'Leaf advancement' of all host trees utilized by caterpillars of a particular species (see Methods for details). As a relative measure, this variable is unitless.
- Within.caterpillar.species.leaf.advancement: For a given caterpillar, the deviation of its host tree’s 'Leaf advancement' from the species-specific mean (i.e. Caterpillar.species.mean.leaf.advancement, see Methods for details). As a relative measure, this variable is unitless.
- Budburst.speed: The rate at which a tree completes budburst, measured as the average daily increase in budburst score from the onset of budburst until completion (see Methods for details). The unit is budburst score per day.
- Budburst.consistency: The consistency of a tree’s budburst timing across years, reflecting whether it consistently buds earlier or later relative to others, or shows variability (e.g., early in one year but average in another). This was quantified as the standard deviation of the tree’s Relative.budburst values across years (see Methods for details).
- Phylogenetic isolation of a tree, defined as the average phylogenetic distance (in millions of years) between the focal tree and all neighboring trees with which it shares direct crown contact (see Supplementary Material for details)
- Dist2Oak: The spatial distance (in meters) from the focal oak tree to its nearest conspecific neighbor.
File: R-code-Unapparent-trees.R
Description: This R script was used to analyze both attached datasets: caterpillar length and pupation timing. The analyses are summarized at the end of the Methods section and are documented within the script itself. All analyses were conducted using R version 4.4.1.
Code/software
The data are in .csv format, which can be opened on Excel
The code is in .R format, which can be opened in RStudio
Access information
Other publicly accessible locations of the data:
- The supplementary document of the corresponding publication
Data was derived from the following sources:
- Fieldwork and lab observations