Ant–plant relationships in an Amazonian rainforest understory: A network approach

Abstract Although tropical rainforest ants are abundant and have high species richness, with their community structure well known at the canopy and ground levels, the understory is frequently neglected. To fill this gap, we looked for ants nesting in this stratum in an Amazonian rainforest and noted the occurrence of colonies in the debris accumulated between the fronds of the palm tree Astrocaryum sciophilum or associated with eight myrmecophytes (i.e., plants that shelter ant colonies in hollow structures called domatia). We analysed these plant–ant relationships by conducting a network approach looking for the degree of specialisation between partners (specialisation index), the differences in intensity between links (weighted nestedness) and the proportion of realised interactions relative to the number of potential interactions (connectance), including ground‐ and canopy‐nesting ants. This results in a highly modular pattern of interactions with one module per plant species based on the 98 ant species recorded. We showed the importance of ground‐nesting species for Astrocaryum , although 40.5% of them sheltered a colony of the arboreal Odontomachus hastatus . Among myrmecophytes, a strong specificity was noted for Hirtella physophora (Chrysobalanaceae) and Maieta guianensis (Melastomataceae) that sheltered at more than 90% Allomerus decemarticulatus and Pheidole minutula , respectively. Cordia nodosa (Boraginaceae) has an intermediary value (45.3% associated with Allomerus octoarticulatus ), whereas Cecropia obtusa (Urticaceae), Duroia longiflora (Rubiaceae), Tachigali paniculata (Fabaceae) and Tococa guianensis (Melastomataceae) can shelter several ant species belonging mostly to a single genus. Tachia guianensis , considered a ‘non‐specialised’ myrmecophyte, shelters species from different genera.