Extrafloral nectar as a driver of ant community spatial structure along disturbance and rainfall gradients in Brazilian dry forest

Abstract

Although extrafloral nectar (EFN) is a key food resource for arboreal ants, its role in structuring ground-nesting ant communities has received little attention, despite these ants also being frequent EFN-attendants. We investigated the role of EFN as a driver of the spatial structure of ground-nesting ant communities occurring in dry forest in north-eastern Brazil. We examined the effects on this relationship of two global drivers of biodiversity decline, chronic anthropogenic disturbance and climate change (through decreasing rainfall). We mapped EFN-producing plants and ant nests in 20 plots distributed along independent gradients of disturbance and rainfall. We categorized ant species into three types according to their dependence on EFN: heavy users, occasional users and non-users. We found a strong relationship between ant dependence on EFN and nest proximity to EFN-producing plants: heavy-users (mean distance 1.1 m) nested closer to EFN-producing plants than did occasional users (1.7 m), which in turn nested closer to EFN-producing plants than did non-users (2.3 m). Neither disturbance nor rainfall affected the proximity of heavy-user nests to EFN-producing plants. Our study shows for the first time that EFN is a key driver of the spatial structure of entire communities of ground-nesting ants.

Revisiting the ideas of trees as templates and the competition paradigm in pairwise analyses of ground-dwelling ant species occurrences in a tropical forest

“…Indeed, L. neotropicum is known to visit EFN of I. edulis in agroecosystems (Sinisterra et al, 2016) and perhaps the same can occur with S. invicta. Ant species that are frequent users of EFN are known to nest closer to EFN-producing plants (Silva et al, 2019). Pachycondyla harpax usually nests underground in the vicinity of trees (Grüter et al, 2018), and although workers forage primarily on the ground, they can also be found on trees (Rocha et al, 2015).…”

Effect of ants on herbivory levels ofInga laurina: the interplay between space and time in an urban area

“…The interplay between the environment and mutualistic ant-partners is a main factor controlling the outcomes in ant-plant interactions (Nogueira et al 2015, Bächtold et al 2016. Most of what we know about the spatiotemporal variation in ant-plant relationships comes from studies in natural areas; however, EFN plants also occur in fragments within urban settings, such as parks (Clarke et al 2008, Silva et al 2019. In a broad sense, urban parks are considered isolated forest habitats surrounded by an urban matrix without terrestrial connections/corridors with natural areas and are susceptible to anthropogenic disturbances (Pacheco & Vasconcelos 2007).…”

Community richness is the main factor determining the structure of ant-plant mutualistic networks along environmental water gradients

“…Therefore, dominant ant species are likely to monopolize the most attractive plant species in the community, displacing subordinate species to less attractive plants (Blüthgen and Fiedler 2004c). At a broad scale, this kind of assortative pairing can predictably shape the patterns of ant-plant interaction along spatial gradients (Dáttilo et al 2013b), especially along those in which the competitive pressure among ant species is also variable (Leal and Peixoto 2017, da Silva et al 2019, Lasmar et al 2021. In this case, ant-plant interactions should become less generalized and form groups of interacting species as the stronger competitive pressure among ant species, with dominant and subordinate ants interacting with a more dissimilar group of plants in the community.…”