DOI: 10.5061/dryad.gb5mkkwpt
title: Discovery-defense strategy as a mechanism of social foraging of ants in tropical rainforest canopies

description: Many hypotheses have been proposed to explain the coexistence of ants
 sharing similar food resources, including ecological trade-offs, however,
 these hypotheses have mostly been tested in ground-dwelling ant
 communities. For instance, the discovery-dominance trade-off hypothesis
 states that species with overlapping food resources differ in their
 ability to find and dominate resources. However, ant species may use
 different strategies to share food resources, including discovery-defense,
 in which the first species to arrive at a food resource maintains control
 of it. Here, we evaluated whether the discovery-dominance trade-off
 hypothesis, or the discovery-defense strategy could be a mechanism that
 promotes coexistence of ant species in the canopy of highly diverse
 tropical forest canopies. We evaluated the succession of ant species on 72
 baits exposed on 24 trees during 13 observation periods (15-195 min) in
 the canopy of trees of a tropical rain forest in Mexico. In general, we
 observed little variation in ant species composition (i.e., low
 β-diversity values) during the 195 minutes of bait exposure. Moreover, we
 found that ant species with the greatest ability to discover new food
 resources were those that showed the greatest aptitude to dominate them.
 These findings empirically show that the discovery-defense strategy can be
 a social foraging strategy in rain forest canopy ants and reject the
 discovery-dominance trade-off. In short, our results highlight the
 importance of the discovery of a food resource in the canopy of a tropical
 rain forest, allowing it to be dominated.
description: We defined six 30-m radius circular plots separated by 250 – 800
 m. At each sampling plot, we chose the four tallest canopy trees, making a
 total of 24 trees. Between May and June 2018, we climbed each of these 24
 trees using the single rope technique. We carried out observations at the
 highest possible point of the tree crown where the climber was safe (21.5
 ± 5 m), usually between 10:00 and 17:00 h. Three baits were placed as far
 as possible from the trunk on different branches of each focal tree (n =
 72 baits). Placing baits on different branches implies exposing them to
 distinct foraging trails, guaranteeing the independence of our
 observations. One tea spoon of bait (a fifty-fifty mixture of tuna with
 honey) was wrapped in a paper napkin and placed on the branches. We
 performed observations on each bait every fifteen minutes, from 15 min
 (first observation) to 195 minutes (thirteenth observation) after
 placement of the bait, in order to evaluate species’ change over time.
 During these observations we counted the number of individuals of each ant
 species at the baits (only if they were in contact with the bait). When it
 was impossible to count the exact number of ant workers because they were
 very tiny
 (e.g., <i>Pheidole</i> and <i>Azteca</i> species)
 and/or numerous individuals were present on the bait (e.g., more than 20
 ant workers), we estimated the number visually, giving a specific number
 for our estimation, for example: “50 workers”. We avoided removing ant
 workers from the baits as much as possible, especially the discoverer
 species (i.e., the first ant species to discover each bait). To
 investigate the pool of ant species from each focal tree, using forceps,
 we collected voucher specimens outside the baits, i.e., ants that were
 foraging on trees and not feeding on the baits, especially at the end of
 the observation period.