Species‐level predation network uncovers high prey specificity in a Neotropical army ant community

Abstract

Army ants are among the top arthropod predators and considered keystone species in tropical ecosystems. During daily mass raids with many thousand workers, army ants hunt live prey, likely exerting strong top-down control on prey species. Many tropical sites exhibit a high army ant species diversity (>20 species), suggesting that sympatric species partition the available prey niches. However, whether and to what extent this is achieved has not been intensively studied yet. We therefore conducted a large-scale diet survey of a community of surface-raiding army ants at La Selva Biological Station in Costa Rica. We systematically collected 3,262 prey items from eleven army ant species (genera Eciton, Nomamyrmex and Neivamyrmex). Prey items were classified as ant prey or non-ant prey. The prey nearly exclusively consisted of other ants (98%), and most booty was ant brood (87%). Using morphological characters and DNA barcoding, we identified a total of 1,103 ant prey specimens to the species level. One hundred twenty-nine ant species were detected among the army ant prey, representing about 30% of the known local ant diversity. Using weighted bipartite network analyses, we show that prey specialization in army ants is unexpectedly high and prey niche overlap very small. Besides food niche differentiation, we uncovered a spatiotemporal niche differentiation in army ant raid activity. We discuss competition-driven multidimensional niche differentiation and predator-prey arms races as possible mechanisms underlying prey specialization in army ants. By combining systematic prey sampling with species-level prey identification and network analyses, our integrative approach can guide future research by portraying how predator-prey interactions in complex communities can be reliably studied, even in cases where morphological prey identification is infeasible. K E Y W O R D Scompetitive release, DNA barcoding, niche differentiation, predator-prey network, prey specialization, species coexistence

Intra‐ and interspecific variation in trophic ecology of ‘predatory’ ants in the subfamily Ponerinae

“…Franks & Bossert, ; Kaspari & O'Donnell, ; Powell, ). Moreover, many species are specialist predators of other ants and almost 50% of Eciton vagans raids target ponerine colonies (Hoenle et al ., ). The current study only included a few of the army ant species that occur at our sites ( E. vagans , Labidus praedator , Labidus coecus and Neivamyrmex sp.)…”

“…predators of other spiders or specific arthropods) can still make determining their exact trophic level difficult. However, niche conservatism is far from ubiquitous and even individual species can exhibit considerable variation in trophic position (Meehan et al ., ; Xiaoqiong et al ., ; Stuble et al ., ; Roeder & Kaspari, ; Hoenle et al ., ). This variation can result from ontogeny (e.g.…”

Detection of prey odours underpins dietary specialization in a Neotropical top‐predator: How army ants find their ant prey

“…The ant species Acromyrmex octospinosus was used as the preferred prey of E. hamatum , as determined by relative frequency of prey items and biomass intake by the colony at the same and different sites throughout Central America (Hoenle et al, 2019; Powell, 2011; Powell & Franks, 2006; Rettenmeyer et al, 1983). The non‐prey ant used in this study was Cephalotes atratus .…”

“…New World army ants (monophyletic group of five genera within subfamily Dorylinae: Borowiec, 2016; Brady, Fisher, Schultz, & Ward, 2014) are well‐established as ecologically important predators of other ants and live in diverse assemblages of up to 20 species in Neotropical forests (Kaspari et al, 2011; Rettenmeyer, 1963; Rettenmeyer, Chadab‐Crepet, Naumann, & Morales, 1983; Schneirla, 1971). Existing data indicate that many army ant species are dietarily specialized on one to a few specific genera of other ants (Breton, Dejean, Snelling, & Orivel, 2007; Hoenle et al, 2019; LaPolla, Mueller, Seid, & Cover, 2002; Powell, 2011; Powell & Clark, 2004; Powell & Franks, 2006; Rettenmeyer et al, 1983), with a few species adding other non‐ant litter invertebrates and social wasps to their diet (Chadab, 1979; Kaspari et al, 2011; O'Donnell, Kaspari, & Lattke, 2005; Rettenmeyer, 1963; Rettenmeyer et al, 1983). Additionally, all species are obligately nomadic group‐predators that roam the forests they inhabit in large collective raids, simultaneously seeking out, attacking and harvesting their preferred ant prey (Rettenmeyer, 1963; Schneirla, 1933, 1971).…”

Army Ants

“…The majority of army ants are specialized ant predators. This seems to be true for all species in the two most speciose genera, Aenictus and Neivamyrmex, and even among the diet of E. burchellii, a species known for its broad prey spectrum, half or more of the prey items are ants [3,4,7]. Arguably, the species with the broadest diet among the New World army ants are those in the genus Labidus, which occasionally even consume plant matter [3,7].…”