Few Ant Species Play a Central Role Linking Different Plant Resources in a Network in Rupestrian Grasslands

Abstract

Ant-plant associations are an outstanding model to study the entangled ecological interactions that structure communities. However, most studies of plant-animal networks focus on only one type of resource that mediates these interactions (e.g, nectar or fruits), leading to a biased understanding of community structure. New approaches, however, have made possible to study several interaction types simultaneously through multilayer networks models. Here, we use this approach to ask whether the structural patterns described to date for ant-plant networks hold when multiple interactions with plant-derived food rewards are considered. We tested whether networks characterized by different resource types differ in specialization and resource partitioning among ants, and whether the identity of the core ant species is similar among resource types. We monitored ant interactions with extrafloral nectaries, flowers, and fruits, as well as trophobiont hemipterans feeding on plants, for one year, in seven rupestrian grassland (campo rupestre) sites in southeastern Brazil. We found a highly tangled ant-plant network in which plants offering different resource types are connected by a few central ant species. The multilayer network had low modularity and specialization, but ant specialization and niche overlap differed according to the type of resource used. Beyond detecting structural differences across networks, our study demonstrates empirically that the core of most central ant species is similar across them. We suggest that foraging strategies of ant species, such as massive recruitment, may determine specialization and resource partitioning in ant-plant interactions. As this core of ant species is involved in multiple ecosystem functions, it may drive the diversity and evolution of the entire campo rupestre community.

Low modularity and specialization in a commensalistic epiphyte–phorophyte network in a tropical cloud forest

“…Therefore, the specificity to the phorophyte is expected to be relatively weak (Wagner et al., ). Low specialization, related to “low intimacy,” seems to be a property common to some mutualistic seed dispersal networks (Blüthgen, Menzell, Hovestadt, Fiala & Bluthgen, ; Jordano, ; Mello et al., ) and between ants and extrafloral nectars (Costa et al., ). This contrasts with other types of interactions that are much more favorable to specificity, such as antagonistic interactions—host plant–pathogen (Benítez‐Malvido & Dáttilo, ), host fish–parasite (Bellay et al., )—and some plant and pollinator systems, in which plants appear to respond more effectively to specialized pollinators than to generalists (Blüthgen et al., ).…”

Nectar quality affects ant aggressiveness and biotic defense provided to plants

“…It is important to note that we carried out the experiment with a plant species that does not naturally bear EFNs. Although plants with EFNs are very common in the Cerrado, several arboreal ants forage on plants that lack EFNs (Camarota et al., ; Costa et al., ; Sendoya et al., ), as they provide other rewards such as floral nectar and fruits. The capacity to exploit these food sources in a heterogeneous environment is directly related to the foraging strategies of ants and their ability to find a resource and recruit to exploit it (Traniello, ).…”

“…We selected 40 individual plants up to 2 m in height spaced at least 5 m apart. The absence of extrafloral nectar does not preclude ant activity, since different ant species commonly forage on the plant surface seeking a variety of resources (Costa et al., ). Therefore, we sampled the set of ant species that naturally forage on the surface of V. elliptica before installing artificial nectaries.…”

Ant diversity in Brazilian tropical dry forests across multiple vegetation domains

“…Interestingly, the few shared species among all TDFs are broadly-ranged, generalist species that can use different types of resources, prey or habitats. Specifically, Camponotus crassus and Cephalotes pusillus are species that use different types of resources in plants such as extrafloral nectaries, trophobiont insects, flowers and fruits (Costa et al 2016). Odontomachus bauri is a generalist epigaeic predator that feeds on leaf litter invertebrates of varying sizes, with preference for arthropods with a similar body size to its own (Brandão et al 2012).…”