DOI: 10.5061/dryad.stqjq2cgm
title: Removing invasive stream macrofauna shifts non-target invertebrate mesofauna through facilitation

description: Positive interactions among non-native species can drive invasional
 meltdowns to the detriment of native biota. Here, we assessed whether
 targeted control of aquatic invasive species (AIS) can benefit native
 species by eliminating synergies among invaders. We did so by monitoring
 changes in the abundance of native and non-native benthic invertebrates
 following the targeted removal of non-native fish and crustaceans in 10
 streams on the island of Oʻahu (Hawaiʻi, USA). Benthic invertebrate
 sampling was conducted in paired control reaches and removal reaches in
 each stream immediately following removals, one month following removals,
 and then at two to three-month intervals for 16 months. Temporal variation
 in the abundance, composition, and diversity of the native and non-native
 invertebrates was compared among streams and between treatment reaches
 using multivariate data visualization and mixed effects models. We
 observed both seasonal shifts in overall community composition and
 treatment-specific effects on the abundance of common taxa that were
 mediated by the number of AIS fish removed. Most notably, as removal of
 non-native poeciliid fish increased, we observed concordant decreases (-32
 ± SE 13%) in non-native caddisfly (Cheumatopsyche analis) and increases
 (122 ± SE 69%) in partially native chironomid midges in the treatment
 reaches relative to the control reaches. Our results provide experimental
 evidence supporting the hypothesis that predation by introduced poeciliids
 on midges indirectly facilitates non-native caddisfly populations via
 competitive release. Our findings indicate that removal of poeciliids
 allows midges to outcompete non-native caddisflies and increase their
 abundance. Our study illustrates that targeted removal of non-native
 species can have cascading negative effects on other introduced taxa.
 Understanding trophic relationships among invasive and native species can
 thus enhance management efforts by maximizing benefits to native species
 relative to effort and cost.
description: # Removing invasive stream macrofauna shifts non-target invertebrate
 mesofauna through facilitation Dataset DOI:
 [10.5061/dryad.stqjq2cgm](https://doi.org/10.5061/dryad.stqjq2cgm) ##
 Description of the data and file structure ## *Study sites* Benthic
 invertebrate sampling was conducted in 10 of 12 watersheds on Oʻahu
 (Hawaiʻi, USA) (Fig. 2), where aquatic invasive species (AIS) removals
 were conducted by Moody et al. (2021). The study sites were selected to
 capture representative variation in hydrology, land cover, and AIS density
 across the island. As described in Moody et al. (2021), each removal site
 consisted of 350m of stream divided into five sections: a 100m upstream
 control, a 25m buffer, a 100m removal reach, a 25m buffer, and a 100m
 downstream control. Locations were chosen in part to incorporate natural
 dispersal obstacles (e.g., plunges, waterfalls) into the buffer zones, and
 the reach lengths were chosen to capture habitat variability typical of
 Hawaiian streams and to allow for comparison to prior studies of AIS and
 native stream fauna in Hawai‘i (Higashi & Nishimoto, 2007). *Watershed
 and in-stream characterization* Watershed characteristics, including
 underlying geology, land use, and annual precipitation, were quantified to
 determine if variation in macroinvertebrate communities corresponded to
 environmental differences among the study sites. Watershed characteristics
 were determined according to resources obtained from the Hawaiʻi Division
 of Aquatic Resources (DAR) and U.S. Geological Survey (USGS). Elevation
 maps (10 m digital resolution) derived from the National Elevation Dataset
 (Gesch et al., 2002) were used to obtain slope and area of each watershed.
 ArcGIS (ArcGIS Desktop: Release 10.1, ESRI, Redlands, CA, USA) was used to
 measure and quantify percentage differences in agriculture, canopy cover,
 development intensity (high and medium), bare land and open spaces based
 on classes 21-24 of the National Land Cover Dataset (2001) (Homer et al.,
 2007), with open spaces encompassing areas subject to light construction
 with vegetation planted for recreational, aesthetic, and erosion control.
 To encompass the net rainfall experienced in the rainy season (October –
 April) and dry season (May – September) (Lau & Mink, 2006), we
 characterized average annual precipitation using the “Online Rainfall
 Atlas of Hawaiʻi” (Giambelluca et al., 2013). ### *Benthic invertebrate
 sampling and characterization* Benthic invertebrates were sampled over
 time in 10 study sites- logistical constraints prevented sampling
 invertebrates in two of the 12 removal sites (Figure 2). Replicate (n = 4)
 benthic invertebrate samples were collected following removals using a
 0.093 m^2^ Surber sampler with 250μm mesh in the removal reach and the
 upstream control reach in each of the 10 study streams. Surber samplers
 were chosen because the reaches were dominated by riffle and run sections
 featuring cobble and gravel bottom. Samples were first obtained in April
 2016, within two weeks of AIS removals, again within a month of AIS
 removals, and subsequently in 2-5 month intervals (hereafter sampling
 “cycles”) from November 2016 through August 2017 (n = 255 unique sampling
 events). During every sampling event, each stream reach was divided into
 four 25 m long quadrants, with one sample taken from a randomly selected
 location in each quadrant. All benthos samples were preserved in 80%
 ethanol and then sorted under a dissecting microscope at 40x
 magnification. All invertebrates were picked from the surrounding
 substrate and enumerated according to identifications made to the lowest
 possible taxonomic resolution (typically genus or species) using Merritt
 and Cummins (2008), Knezovic et al. (2015), Landcare Research (2017), and
 CPIE Project (2011). Due to the difficulties of identifying larval
 Hawaiian Chironomidae, all chironomid taxa were only identified to family
 level and were assumed to be a mix of native and introduced species,
 following results of previous surveys in the study region (Englund et al.
 2007, Brasher et al. 2004). Notably, prior surveys of O’ahu and Maui
 streams found that Chironominae and Orthocladiinae dominated midge
 communities (O’ahu: 100%, Maui: 99.8%), and that Tanypodinae were
 extremely rare (O’ahu: 0%, Maui: 0.2% ), suggesting that predatory midges
 likely made up a marginal proportion of the samples taken in our study
 streams (Wolff 2012). ### Files and variables #### File:
 stream.covariate_dryad.csv **Description:** This dataset contains
 summarized information about the geography, watershed, and environmental
 characteristics of the study sites. Missing values that were not able to
 be measured by the field teams are indicated by "n/a" where
 applicable.  ##### Variables * Latitude: Latitude of the stream reach in
 decimal degrees * Longitude: Longitude of the stream reach in decimal
 degrees * Site: Name of the stream  * bottom structure: Dominant benthic
 substrate in accordance with the Wentworth scale * DRNAREA: Area of the
 site drainage basin in square kilometers * ELEV: Elevation of the site in
 meters above sea level * BSLDEM10M: Mean basin slope calculated from 10m
 topographic layer * SLOP30_10M: Percentage of area with a slope of 30% or
 greater calculated from a 10m topographic layer * PRECIP: Mean annual
 precipitation in mm * BASINPERIM: Perimeter of the basin in km *
 IMPNLCD01: % of the basin with impervious surface * LC01DEVMD: % of the
 basin with medium development * LC01DEVHI: % of the basin with high
 development * LC01BARE: % of the basin with bare ground * LC01EVERG: % of
 the basin with evergreen forest * LC01CROP: % of the basin with row crop
 agriculture * tempMean: average within stream water temperature * tempCV:
 coefficient of variation of stream water temperature * tempMax: maximum
 observed stream water temperature * Temp10: 10th percentile of stream
 water temperature * Temp50: 50th percentile of stream water temperature *
 Temp90: 90th percentile of stream water temperature * TSSave: Average
 total suspended solids in mg/L * TSScv: Coefficient of variation in total
 suspended solids * SRPave: Average soluble reactive phosphorus in mg/L *
 SRPcv: Coefficient of variation in soluble reactive phosphorus * NO3ave:
 Average nitrate concentration in mg/L * NO3cv: Coefficient of variation in
 nitrate * PreNH4Removal: Ammonium concentration in mg/L in the removal
 reach prior to removal * PreNH4UpCon: Ammonium concentration in mg/L in
 the upstream control reach prior to removal * PostNH4Removal: Ammonium
 concentration in mg/L in the removal reach after removal *
 PostNH4UpCon: Ammonium concentration in mg/L in the upstream control reach
 after removal * PreNO3Removal: Nitrate concentration in mg/L in the
 removal reach prior to removal * PreNO3UpCon: Nitrate concentration in
 mg/L in the upstream control reach prior to removal *
 PostNO3Removal: Nitrate concentration in mg/L in the removal reach after
 removal * PostNO3UpCon: Nitrate concentration in mg/L in the upstream
 control reach after removal * PreSRPRemoval: Soluble reactive phosphorus
 concentration in mg/L in the removal reach prior to removal *
 PreSRPUpCon: Soluble reactive phosphorus concentration in mg/L in the
 upstream control reach prior to removal * PostSRPRemoval: Soluble reactive
 phosphorus concentration in mg/L in the removal reach after removal *
 PostSRPUpcon: Soluble reactive phosphorus concentration in mg/L in the
 upstream control reach after removal * PreTSSRemoval: Total suspended
 solids concentration in mg/L in the removal reach prior to removal *
 PreTSSUpCon: Total suspended solids concentration in mg/L in the upstream
 control reach prior to removal * PostTSSRemoval: Total suspended solids
 concentration in mg/L in the removal reach after removal *
 PostTSSUpcon: Total suspended solids concentration in mg/L in the upstream
 control reach after removal #### File: stream.invertebrate_dryad.csv
 **Description:** This dataset contains summarized information regarding
 the invertebrates collected and identified at each of the sampling reaches
 over the course of the study ##### Variables * Date: The date on which
 sampling occurred in American format * Season: The season when sampling
 occurred (Fall, Winter, Spring, Summer) * Month: The month in which
 sampling occurred * Day: The day of the month in which sampling occurred *
 Year: The year in which sampling occurred * Site: The name of the site
 where the sample was collected * Treatment: The specific reach where the
 sample was collected, either RM (removal) or UC (upstream control) *
 Replicate: The replicate number for the benthos sample taken, typically
 four samples were taken for each unique combination of sampling date,
 site, and reach.  * Sample: The full unique identifier code for a sample,
 combining the site name, reach code, date, and replicate number.  * OTU:
 The operational taxonomic unit assigned to the macroinvertebrate, e.g.,
 the lowest taxonomic resolution the animal was identified to.  * Count:
 The number of individuals in the sample that were identified to that OTU.
 In cases of partial specimens, only heads were counted.  * Status: The
 geographic origin of the OTU, either I (invasive/non-native), N (native),
 or U (unknown).