DOI: 10.5061/dryad.xwdbrv1f7
title: Data from: A whole-ecosystem method for experimentally suppressing ants on a small scale

description: Ant suppression experiments have emerged as a powerful method for
 assessing the role of ants in ecosystems. However, traditional methods
 have been limited to canopy ants, and not assessed the role of ants on and
 below ground. Recent advances have enabled whole-ecosystem ant suppression
 in large plots, but large-scale experiments are not always feasible. Here,
 we develop a small-scale, whole-ecosystem suppression method. We compare
 techniques for monitoring suppression experiments, and assess whether
 habitat complexity in oil palm influences our method’s effectiveness. We
 conducted ant suppression experiments in oil palm agroforestry in Sumatra,
 Indonesia. We used targeted poison baits, a physical barrier, and canopy
 isolation to suppress ants in 4m-radius arenas around single palms. We
 sequentially tested three suppression methods that increased in intensity
 over 18 months. We sampled ant abundance before and after suppression by
 fogging, using pitfall traps, and extracting soil monoliths. We also
 monitored ants throughout the experiment by baiting. We tested the soil
 for residual poison and monitored other invertebrates (Araneae,
 Coleoptera, Orthoptera, and Chilopoda) to test for cross-contamination.
 Plots were established under four oil palm management treatments that
 varied in their habitat complexity: reduced, intermediate, and high
 understory complexity treatments in mature plantation, and a
 recently-replanted plantation. Post-treatment ant abundance was 92% lower
 in suppression than control plots. Only the most intensive suppression
 method, which ran for the final nine months, worked. Baiting rarely
 reflected the other monitoring methods. The treatment negatively affected
 Orthoptera, but not other taxa. We detected no residual poison in the
 soil. Coleoptera abundance increased in suppression plots post-treatment,
 potentially due to reduced competition with ants. Our findings were
 consistent across management treatments. We developed a whole-ecosystem
 method for suppressing ants on a small scale in oil palm plantations. Our
 method represents a significant advance; previous reductions in ant
 abundance have not exceeded 38%. We provide the first example of ants
 being experimentally suppressed belowground. Baiting is not adequate for
 assessing suppression effectiveness, and testing a range of taxa for
 confounding impacts is important. Our study acts as a blueprint for
 developing suppression methods for other taxa, which offer unique insights
 into community ecology.
description: We conducted ant
 suppression experiments in oil palm agroforestry at the Biodiversity and
 Ecosystem Function in Tropical Agriculture (BEFTA) programme
 (oilpalmbiodiversity.com) in Sumatra, Indonesia. We used targeted poison
 baits, a physical barrier, and canopy isolation to suppress ants in
 4m-radius arenas around single palms. We sequentially tested three
 suppression methods that increased in intensity over 18 months, and the
 suppression worked for the final method which lasted for nine
 months. We
 established 24 suppression plots and 24 control plots. These were evenly
 split over four oil palm management treatments that varied in their
 habitat complexity: <b>Reduced
 complexity (Reduced): </b>Mature first-generation plantation with
 all understory vegetation removed by spraying herbicide. <b>Normal
 complexity (Normal): </b>Mature first-generation plantation with
 understory vegetation removed from the harvesting paths and harvesting
 circle (a ~1.5m radius area around the base of each palm) using herbicide,
 and large woody vegetation removed manually. Other vegetation was allowed
 to grow. This is standard industry practice in these estates.
 
 <b>Enhanced complexity (Enhanced):</b> Mature first-generation
 plantation with the same understory management as the normal complexity,
 except harvesting paths and circles were cleared by strimming rather than
 herbicide. <b>Replanted
 (Replanted): </b>Young second-generation plantation with the same
 understory vegetation management as normal complexity plots.
 We sampled ant
 abundance before and after suppression by fogging (six trays per plot),
 using pitfall traps (three traps per plot left for three days each), and
 extracting soil monoliths (two per plot). We also monitored ants
 throughout the experiment by baiting with sugar and tuna baits in the
 canopy and on the ground (four plates per plot in total). For baiting, we
 identified two conspicuous species: Yellow Crazy Ant (<i>Anoplolepis
 gracilipes</i>) and Weaver Ant (<i>Oecophylla
 smaragdina</i>). We monitored the most abundant non-ant
  invertebrate taxa (Araneae and Coleoptera in the canopy, Coleoptera and
 Orthoptera on the ground, and Chilopoda belowground) to test for
 cross-contamination. We also tested the soil for residual poison and found
 that there was none.
description: There are five datasets
 which correspond to the different sampling methods (fogging, pitfalls,
 monoliths, and baiting). Fogging – each row represents one
 palm (i.e. the values for the six trays were summed) Pitfalls – each row represents
 one pitfall trap Monoliths (pre-treatment) – each
 row represents a single observation of an invertebrate Monoliths (post-treatment) – each
 row represents one monolith Baiting – each row represents one
 bait plate