Seasonal variation in the ant–plant interaction network mediated by extrafloral nectaries in the southern Sonoran Desert

Ants, a prominent insect group, play important roles in various terrestrial ecosystems, by engaging in diverse biotic interactions, such as those involving plants bearing extrafloral nectaries (EFNs). This study investigates the seasonal dynamics of this interaction throughout the dry and rainy seasons in a southern Sonoran Desert site. Results indicate that despite a relatively low coverage of EFN-bearing plants (4.97% ± 4.60), interactions between ants, and these plants are frequent, involving 31% of the perennial plant community (35 species) and 54% of the ant community (35 species). The cactus family exhibited the highest species richness (7 of 11 species) with EFNs in the study area. The location of EFNs varied among plant species and were associated with both vegetative and reproductive organs. Employing selective trapping for ants that forage on plants bearing EFNs, a higher ant species richness was recorded during the rainy season (19 vs 12 spp.). The network’s topology is associated with plant phenology, and slight seasonal differences in network structure parameters were observed. Seasonal variation in the interaction align with the phenology of EFN-bearing plants. Factors such as water availability could influence competition and, consequently, the inter-season variation in the number and dependencies of ant–plant interactions. Only two species were consistently recorded in both seasons within the core of generalists: the cactus Cylindropuntia fulgida and the ant Forelius pruinosus. Given the substantial involvement of ants with EFN-bearing plants, this association emerges as a fundamental component within the community of this desert site.