DOI: 10.5061/dryad.02v6wwqhz
title: Data from: Plant invasion overrides drought in suppressing arthropod abundance and richness

description: Plant invasions and drought are global change stressors that alter plant
 availability and quality, habitat structure, and micro-site conditions,
 with likely cascading effects on arthropod diversity, yet few studies have
 disentangled their relative impacts. We quantified the effects of
 experimental plant invasion (by Imperata cylindrica, cogongrass) and
 simulated drought, imposed singly and in combination, on abundance and
 morphospecies richness of arthropod communities, functional groups, and
 individual taxa in regenerating longleaf pine understory located in humid,
 subtropical central Florida, USA. Across all three scales of organization,
 invasion emerged as a negative stressor, both alone and in combination
 with drought, while drought alone had mostly positive effects on
 arthropods. At the community scale, arthropod abundance and richness were
 74% and 55% lower, respectively, in invaded than uninvaded plots
 (averaging over drought) two years after initiation of invasion, while
 drought had no negative effect. Herbivores, pollinators, and predators had
 lower abundances (by 78%, 48%, and 73%, respectively) and richness (by
 63%, 29%, and 67%) in invaded than uninvaded plots by the second year of
 invasion. Herbivorous hemipterans, caterpillars, and beetles were more
 negatively affected by invasion than grasshoppers, while for pollinators,
 flies (rather than moths or bees) drove the negative response, exhibiting
 lower abundance and richness when both stressors were present. There was
 also a cascading negative effect of invasion on the abundances of
 predatory wasps and spiders, and the richness of predatory wasps.
 Conversely, several disparate taxa responded positively to drought without
 invasion, despite significantly warmer and drier conditions under drought.
 The pronounced negative effect of invasion on arthropod communities was
 driven partly by its reduction of resident plant richness, which was in
 turn positively correlated with arthropod abundances and richness. These
 results suggest plant invasion as one important driver of arthropod
 decline in a rapidly changing world.
description: # Data from: Plant invasion overrides drought in suppressing arthropod
 abundance and richness Dataset DOI:
 [10.5061/dryad.02v6wwqhz](https://doi.org/10.5061/dryad.02v6wwqhz) ##
 Description of the data and file structure This dataset quantifies the
 effects of experimental plant invasion (by *Imperata cylindrica*,
 cogongrass) and simulated drought, imposed singly and in combination, on
 abundance and morphospecies richness of arthropod communities, functional
 groups, and individual taxa in regenerating longleaf pine understory
 located in humid, subtropical central Florida (Gainesville), USA. The data
 represent the outcomes of a fully factorial common garden experiment in
 which plots were exposed to the following treatments: 1) total controls
 (no invasion, no drought), 2) invasion only, 3) drought only, and 4)
 invasion and drought together. The data were used to assess both the
 separate and interactive effects of these two stressors on local arthropod
 communities, including herbivores, pollinators, and predators, as well as
 to assess how invasion and drought affected plot abiotic conditions (soil
 moisture, light availability, temperature, and humidity), and co-occurring
 plant richness. ### Files and variables #### File:
 Data_For_Repository_Arthropods.xlsx **Description:** This file contains
 arthropod abundance and richness counts by individual plots and treatment
 type. ##### Variables * Year: Year during which data were collected -
 Season: Season of the year during which data were collected * Date:
 Variable assigned to dates to indicate unique sampling periods - Plot:
 Plot numbers (40 plots total in experiment) * Block: Block numbers (10
 blocks total in experiment) - Trt: Abbreviation of treatment types
 assigned to plots (D = drought; C = cogongrass; A = Ambient precipitation;
 D = drought imposed. * Drought: Indicates that drought conditions were
 imposed with rainout shelters - Invasion: Indicates that the cogongrass
 invasion was imposed via the sowing of plugs * arthroID: Identifier given
 to each unique group of arthropods used in the morphospecies richness
 analyses - functional: Functional groups assignations for arthropod groups
 * abundance: Counts of arthropods by arthroID type - sqrtabun: Square root
 transformation of counts #### File:
 Data_For_Repository_LightAvailability.xlsx **Description:** This file
 contains light availability (photosynthetically active radiation) by
 individual plots and treatment type. ##### Variables * date: Date
 (m/dd/yyyy) on which data were collected - dateid: Month of data
 collection * sample bout: Variable assigned to dates to indicate unique
 sampling periods - plot: Plot numbers (40 plots total in experiment) *
 block: Block numbers (10 blocks total in experiment) - trt: Abbreviation
 of treatment types assigned to plots (D = drought imposed; C = cogongrass
 invasion imposed; A = Ambient precipitation) * sampleloc: One of four
 sample locations within plots at which light measurements were taken,
 denoted A-D. Sample locations were averaged over to get a single estimate
 per plot. - drought: Indicates that drought conditions were imposed with
 rainout shelters * invasion: Indicates that the cogongrass invasion was
 imposed via the sowing of plugs - light-reduced: Measurement of
 photosynthetically active radiation taken within plots versus outside
 plots in full sun * perlightreduced: Percentage by which light was reduced
 inside versus outside of plots - lightavailable5: Percentage of light
 available versus full sun at a height of ½ off the ground *
 lightavailable: Percentage of light available versus full sun at ground
 levels - sqrt5: Square root transformation of light available5 *
 sqrtground: Square root transformation of light available #### File:
 Data_For_Repository_SoilMoisture.xlsx **Description:** This file contains
 volumetric soil moisture by individual plots and treatment type. #####
 Variables * Year: Year in which volumetric water content measurements were
 taken - Season: Season in which volumetric water content measurements were
 taken * datechron: Variable assigned to dates, putting them in
 chronological order - Trt: Abbreviation of treatment types assigned to
 plots (D = drought imposed; C = cogongrass invasion imposed; A = Ambient
 precipitation) * drought: Indicates that drought conditions were imposed
 with rainout shelters - invasion: Indicates that the cogongrass invasion
 was imposed via the sowing of plugs * plot: Plot numbers (40 plots total
 in experiment) - block: Block numbers (10 blocks total in experiment) *
 vwc: Volumetric water content within plots - sqrtvwc: Square root
 transformation of volumetric water content #### File:
 Data_For_Repository_Temp_Hum_RawData.xlsx **Description:** This file
 contains temperature and humidity data for individual plots and treatment
 types. ##### Variables * date: Date of data collection (comment
 included: Removed data points logged after buttons were removed from the
 plots.) - time: Time of data collection * ampm: Indicates ante meridiem
 (before mid-day) and post meridiem (after mid-day) timing of data
 collection - timeconc: A column that concatenates the time and ampm
 columns * plot: Plot numbers (40 plots total in experiment) - trt:
 Abbreviation of treatment types assigned to plots (D = drought imposed; C
 = cogongrass invasion imposed; A = Ambient precipitation) * rh: Percent
 relative humidity measurements taken in plots - temp: Temperature in
 Celsius taken in plots