Leaf‐cutting ants negatively impact the regeneration of the Caatinga dry forest across abandoned pastures

Abstract

The mechanisms affecting forest regeneration in human‐modified landscapes are attracting increasing attention as tropical forests have been recognized as key habitats for biodiversity conservation, provision of ecosystem services, and human well‐being. Here we investigate the effect of the leaf‐cutting ants (LCA) Atta opaciceps on regenerating plant assemblages in Caatinga dry forest. Our study encompassed 15 Atta opaciceps colonies located in landscape patches with a gradient of forest cover from 8.7% to 87.8%, where we monitored regenerating individuals (seedlings and saplings of woody and herbaceous plants) in different habitats (nests, foraging areas, and control areas) over one year. We recorded 2,977 regenerating plant individuals, distributed among 55 species from 23 families. Herbaceous plants represented 82.1% and 58.2% of the total number of individuals and species, respectively. Species richness of both the whole and herbaceous plant assemblages increased along the forest cover gradient, but without difference between the habitats. Total plant abundance was highest in control areas followed by foraging areas and nests and this pattern held for both woody and herbaceous plants. Although forest cover did not influence the abundance of herbaceous plants and the whole plant assemblage, it positively affects woody plant abundance across control areas. Forest cover and habitat changed species composition of both the entire regenerating and the herbaceous assemblages. These results together indicate that LCA negatively impact regenerating plant assemblages, particularly in those sites with increased forest cover. As LCA proliferate in human‐modified landscapes, they may prevent plant regeneration of disturbed areas.

Interplays between Atta ants (Formicidae: Attini), soils and environmental properties in the Brazilian Neotropics: a preliminary assessment

“…Our results illustrate a greater association of A. opaciceps with the core semiarid area, with hotter and drier climates (Figure 5b) (Siqueira et al, 2018), whereas the other species are present in the transitional ecotones with the adjacent biomes. In addition to this occurrence in central Caatinga, A. opaciceps is well-adapted to anthropogenic landscapes (Knoechelmann et al, 2020), with a preference for open, shrubby vegetation, where Atta may contribute to maintaining this spatial pattern of vegetation, as postulated by Knoechelmann et al (2020).…”

Does mining waste concentration in the soil interfere with leaf selection by Acromyrmex subterraneus (Formicidae)?

“…One of the herbivores of seedlings in revegetation programs in Brazil comes are leaf‐cutting ants, represented by Atta and Acromyrmex (Myrmicinae, Formicidae) (Coan et al., 2004; Costa et al., 2017; Fleury, Silla, Rodrigues, do Couto, & Galetti, 2015; Knoechelmann et al., 2020; Leal et al., 2014; de Lima Júnior et al., 2019), which are the most abundant herbivore in forest edges and small fragments of different phytophisionomies (da Silva, Silva, Ribeiro‐Neto, Wirth, & Leal, 2018; Siqueira et al., 2017, 2018; Wirth et al., 2008). In disturbed habitats, their abundance and action as herbivores is even more prominent (Costa et al., 2008; Leal et al., 2014), as they are less attacked by predators (Wirth et al., 2008) and parasitoids (Almeida et al., 2008).…”

Impoverished woody seedling assemblages and the regeneration of Caatinga dry forest in a human‐modified landscape

“…In our focal landscape, introduced goats have been reported to reduce the biomass and diversity of herb assemblages (Menezes et al, 2020), with a combination of shifting cultivation and goat pressure as the anecdotal drivers for the establishment of assemblages dominated by unpalatable perennial herbs such as Herissantia crispa (Malvaceae). Moreover, leaf‐cutting ants respond positively to human disturbances in this landscape, reducing seedling abundances across extensive foraging areas (Knoechelmann et al, 2020; Siqueira et al, 2017, 2018). As the seedling bank declines in response to human disturbances, forest regeneration becomes more dependent on adult resprouting, a common mechanism across dry forests (Murphy & Lugo, 1986; Sampaio et al, 1993), and a reasonable explanation for the current dominance of P. moniliformis adults in the Catimbau National Park, as it resprouts vigorously (Barros et al, 2021; Souza et al, 2019).…”