DOI: 10.5061/dryad.9ghx3ffpk
title: Tree species richness around urban red maples reduces pest abundance but does not enhance biological control

description: Urban trees often host greater insect pest abundance than trees in rural
 forests. This may be due, in part, to differences in tree diversity and
 canopy cover between these settings. Urban trees are often planted in
 isolation or monoculture, which favors pest accumulation. The gloomy
 scale, Melanaspis tenebricosa Comstock, is a pest of urban red maples
 (Acer rubrum L.) that is abundant where impervious surfaces dominate the
 local landscape. Increasing tree diversity and canopy cover around urban
 red maples may reduce gloomy scale abundance by supporting natural enemy
 communities. We investigated the effect that surrounding tree species
 richness and tree canopy cover had on gloomy scale abundance, natural
 enemy abundance, and biological control in red maple trees in Raleigh, NC,
 USA. We collected scales and natural enemies from red maples that spanned
 a gradient of tree species richness, canopy cover, and impervious surface
 values. We also measured gloomy scale parasitism and predation of sentinel
 prey in red maple canopies. Greater tree species richness and canopy cover
 were associated with lower gloomy scale density. Red maples in diverse
 settings also hosted fewer scales per natural enemy. Parasitoids were less
 common in maples in diverse settings, but generalist predator abundance
 was unaffected by tree diversity. Finally, tree species richness and
 canopy cover did not increase biological control of scales or sentinel
 prey. Our findings suggest that higher tree diversity and greater canopy
 cover may reduce gloomy scale density, but this is not entirely explained
 by the effects of natural enemies and biological control.
description: Contact person: Caleb Wilson Email: c.wilson@uky.edu Geographic area:
 Raleigh, NC. USA Study: Wilson et al. 2023 "Tree species richness
 around urban red maples reduces pest abundance but does not enhance
 biological control." Urban Forestry and Urban Greening. Support: This
 research was funded by grants provided to SDF and AGD from the United
 States Department of Agriculture, National Institute of Food and
 Agriculture (award numbers: 2018-70006-28914, 2016- 70006-25827).
 Components of this work were supported by a Postdoctoral Fellowship (grant
 no. 2019-67012-29633) from the U.S. Department of Agriculture, National
 Institute of Food and Agriculture to MGJ. Description: This spreadsheet
 contains all data needed to run statistical analyses presented in the
 paper. Data are separated into different tabs based upon the table where
 the data were used or the type of analysis conducted. Data sources: Backe
 and Frank 2019: 32 red maples. [https://doi.org/10.1093/ee/nvz094] Used
 live adults and nymphs recorded on branches from 2015 and 2014 growth.
 Counts were recorded in 2017. Just-Cultivar: 28 red maples. Previously
 unpublished data collected by MGJ and ECL. Gloomy scale data were
 collected on red maple trees in the spring of 2018 and 2020. We used 2020
 counts for all trees except for two (tree IDs: A1, A18) which were only
 sampled in 2018 and not in 2020. Water: 17 red maples Previously
 unpublished data from a red maple watering project conducted over the
 years 2017 - 2020. Gloomy scale data used in the analysis for this paper
 are from January 2020. Wilson2020: 11 red maples. CJW collected gloomy
 scale data on red maple trees on the campus of North Carolina State
 University in spring of 2020. Long2019: 7 red maples.
 [https://doi.org/10.1016/j.scitotenv.2018.12.293]Counts from red maples
 were collected in 2016 Explanation of column names by spreadsheet tab:
 "All Data for Tables 2 and 3": ``` NOTE1: ALL PREDICTORS WITH
 "_s" AFTER THE NAME ARE PREDICTORS THAT HAVE BEEN SCALED AND
 CENTERED. For example, "Rare20Sp_s "is just "Rare20Sp"
 after scaling and centering was completed in R. NOTE2: All NA's in
 this tab correspond to 5 trees where scales were collected, but natural
 enemy data was not collected. Study:Where the gloomy scale data for this
 tree were pulled from. Data sources are explained above in "Data
 sources" Site: The name given to the sampled tree. All trees are red
 maples. The same name is kept from the data source that the tree was
 pulled from. Rare20Sp: Rarefied tree species richness after running
 through iNEXT in R. For observed richness use "Richness" or for
 observed surrounding richness use "Srichness". RareType: A
 grouping used for plotting purposes. Sites are grouped based on if their
 surrounding rarefied tree species richness is &gt; or &lt; 10
 species. Rare20Sp_R Rarefied tree species richness rounded to the nearest
 integer value. Used for plotting and not for analysis. Latitude: The
 latitude of each tree in decimal degrees. Values are pulled from google
 earth and are therefore in the WGS84 projection. Longitude: The longitude
 of each tree in decimal degrees. Values are pulled from google earth and
 are therefore in the WGS84 projection. GloomyTotal: The total number of
 gloomy scales recorded over the total twig length that scales were
 counted. TotalLengthCM: The total twig length over which gloomy scales
 were counted (in centimeters) ScalesPerCM: GloomyTotal divided by
 TotalLengthCM ScalesPerCM_R: ScalesPerCM rounded to the nearest integer
 value. Used for plotting only. ScalesPerEnemy: GloomyTotal divided by
 TotalEnemies ScalesPerPtoid: GloomyTotal divided by ParasitoidTotal
 ScalesPerGeneralist: GloomyTotal divided by NonPtoidEnemies
 ParasitoidTotal: The total number of parasitoids recorded from beat
 samples (both collection rounds pooled TotalEnemies: The total number of
 natural enemies (ParasitoidTotal + NonPtoidEnemies) NonPtoidEnemies: All
 natural enemies that are not parasitoids. Also referred to as
 "generalists" in the paper Srichness: The observed tree species
 richness surrounding all red maples within a 25 m buffer. NOTE: This does
 not include richness contributed by the focal red maple. For example, if
 there was only one other tree species surrounding the focal red maple, the
 Srichness value would be 1 because there is only one other species
 surrounding the red maple. Sdensity: The observed abundance of trees
 surrounding all red maples within a 25 m buffer. NOTE: This count does not
 include the focal tree. For example, if there was one other tree
 surrounding the focal red maple the Sdensity value would be 1 and not 2
 because this value does not encompass the focal tree. Imp25: The
 proportion of impervious surface cover at a 25 m radius around all red
 maples MeanCanopy25: The percent of canopy cover withn a 25 m radius
 around all red maples. CanopyType: A categorical grouping used for
 plotting purposes to separate red maples that had &gt; or &lt; 20
 % canopy cover within a 25 m radius PerImp25: Imp25 multiplied by 100 to
 produce a percentage Richness: The observed tree species richness within a
 25 m buffer. Includes the focal tree. Density: The observed abundance of
 trees within a 25 m buffer. Includes the focal tree. ``` Drosophila data -
 Table 4 NOTE: ALL PREDICTORS WITH "\_s" AFTER THE NAME ARE
 PREDICTORS THAT HAVE BEEN SCALED AND CENTERED. For example,
 "Rare20Sp\_s "is just "Rare20Sp" after scaling and
 centering was completed in R. ``` Tree: The name of the tree that
 Drosophila were placed in. All trees are red maples Treatment: Refers to
 if the Drosophila card was open or placed in a cage. All cards in this
 spreadsheet tab are open cards. See the Drosophila - open_closed tab for
 closed card data. Round The name of the experiment round. The first round
 is "A" and rounds continue in alphabetical order. Date out: The
 date that the Drosophila were placed in the tree Date Removed: The date
 that the Drosophila were removed from the tree Initial count: The initial
 count of Drosophila when placed in trees BinRemoved24: Whether or not any
 Drosophila were removed at 24 hours. Values with 1 indicate removal
 occurred, values with 0 indicate no removal occurred 1 day count: The
 number of Drosophila on cards at 24 hours. BinRemoved48: Whether or not
 any Drosophila were removed at 48 hours. Values with 1 indicate removal
 occurred, values with 0 indicate no removal occurred two_day_count: The
 number of Drosophila on cards at 48 hours. Removed48: The number of
 Drosophila removed at 48 hours. PropRemoved48: The proportion of
 Drosophila removed at 48 hours GloomyTotal: The total number of gloomy
 scales recorded over the total twig length that scales were counted.
 TotalLength:The total twig length over which gloomy scales were counted
 (in centimeters) ScalesPerCm: GloomyTotal divided by TotalLength
 Srichness: The observed tree species richness surrounding all red maples
 within a 25 m buffer. NOTE: This does not include richness contributed by
 the focal red maple. For example, if there was only one other tree species
 surrounding the focal red maple, the Srichness value would be 1 because
 there is only one other species surrounding the red maple. Sdensity: The
 observed abundance of trees surrounding all red maples within a 25 m
 buffer. NOTE: This count does not include the focal tree. For example, if
 there was one other tree surrounding the focal red maple the Sdensity
 value would be 1 and not 2 because this value does not encompass the focal
 tree. MeanCanopy25: The percent of canopy cover withn a 25 m radius around
 all red maples. CanopyType: A categorical grouping used for plotting
 purposes to separate red maples that had &gt; or &lt; 20 % canopy
 cover within a 25 m radius Rare20Sp: Rarefied tree species richness after
 running through iNEXT in R. RareType: A categorical grouping used for
 plotting purposes to separate red maples that had &gt; 7 surrounding
 species or &lt; 7 surrounding species within a 25 m radius. ``` Scale
 parasitism - Table 4 NOTE: ALL PREDICTORS WITH "\_s" AFTER THE
 NAME ARE PREDICTORS THAT HAVE BEEN SCALED AND CENTERED. For example,
 "Rare20Sp\_s "is just "Rare20Sp" after scaling and
 centering were completed in R. Page 1 and 2 watermark is just layout style
 not of significance to the analysis. ``` Tree: The name of the tree that
 scales and parasitoids were checked in. Rare20Sp: Rarefied tree species
 richness after running through iNEXT in R. MeanCanopy25: The percent of
 canopy cover withn a 25 m radius around all red maples. ScalesPerCM:
 GloomyTotal divided by TotalLength. ParasitoidsBeat: The abundance of
 parasitoids recorded from both beat samples collected in the tree.
 TotalParasitoids_twig: The total number of parasitoid life stages found
 underneath gloomy scale tests across all twigs checked on the tree.
 TotalHealthy_twig: The total numer of healthy gloomy scales found across
 all twigs checked on the tree. TotalChecked: The total number of scales
 checked for parasitism on the tree. PercentParasitized: The percentage of
 parasitized scales out of 50 checked scales. GloomyTotal The total number
 of gloomy scales recorded over the total twig length that scales were
 counted. TotalLength The total twig length over which gloomy scales were
 counted (in centimeters). ``` Drosophila - open\_closed: Data in this tab
 were used to assess if greater removal of Drosophila adults occurred in
 open bait cards as opposed to closed bait cards. ``` Tree:The name of the
 tree that scales and parasitoids were checked in. Treatment: Refers to if
 the Drosophila card was open or placed in a cage. Round: The name of the
 experiment round. The first round is "A" and rounds continue in
 alphabetical order. Date out: The date that the Drosophila were placed in
 the tree Date Removed: The date that the Drosophila were removed from the
 tree Initial count: The initial count of Drosophila when placed in trees 1
 day count: The number of Drosophila on cards at 24 hours. 2 day count: The
 number of Drosophila on cards at 48 hours. Bin24: Whether or not any
 Drosophila were removed at 24 hours. Values with 1 indicate removal
 occurred, values with 0 indicate no removal occurred. Bin48: Whether or
 not any Drosophila were removed at 48 hours. Values with 1 indicate
 removal occurred, values with 0 indicate no removal occurred. Removed48:
 The total number of removed Drosophila at 48 hours. PropRemoved48: The
 proportion of Drosophila removed at 48 hours ``` ScaleComparison2018-2020:
 Data in this tab were used to determine if scale densities differed
 between 2018 and 2020 on trees that were sampled in both years. ``` Study:
 The dataset that scale data came from. See "data sources" at the
 top of the readme file for additional details ScalesPerCm: The number of
 scales counted on each tree divided by the total length (in centimeters
 over which scales were counted). Year: The year that the
 "ScalesPerCm" data correspond to. ```