The Potential Role of Scattered Trees for Ant Conservation in an Agriculturally Dominated Neotropical Landscape

Abstract

Although biological conservation has traditionally focused on the protection of pristine areas, it is becoming increasingly evident that efforts should also be made toward the maintenance of biological diversity in human‐managed ecosystems. We evaluated the potential role of scattered, remnant trees in enhancing ant diversity in agricultural lands within a biodiversity hotspot, namely the Cerrado savannas of central Brazil. Ant collections were performed in, beneath, and away from the crowns of a native tree species growing in planted pastures, soy fields, and in small (<400 ha) savanna reserves. Significantly more ant species were found beneath than 30 m away from scattered trees. The magnitude of this effect was similar in soy fields and in pastures at all scales of our analyses, except at the landscape scale where the effect was comparatively greater in soy fields. Most of the species that occurred more frequently beneath than away from trees nest on ground, indicating that the conservation value of scattered trees goes beyond the mere protection of arboreal ant species. Soy plantations presented a particular species‐poor ground‐dwelling fauna when compared with savannas, whereas differences in the number and composition of arboreal species were less marked. In contrast, the diversity of arboreal‐ and ground‐dwelling ants recorded in and beneath pasture trees was nearly as high as the one found in savannas. It is suggested that pasture trees can have an important value for ant conservation off reserves, particularly in regions where most of the native vegetation has already been cleared.

The importance of scattered trees for biodiversity conservation: A global meta‐analysis

“…Our meta‐analysis revealed that scattered trees have strong positive effects on the abundance and richness of vertebrates, arthropods and woody plants, consistent with the results of previous studies (e.g. Barth et al., ; Fischer, Stott, et al., ; Frizzo & Vasconcelos, ; Lumsden & Bennett, ; Schlawin & Zahawi, ). For these groups, local abundance was 60%–430% greater and richness was 50%–100% higher in areas with scattered trees than in open areas.…”

“…birds and bats; Fischer, Stott, et al., ), or for the same taxon but for different areas (e.g. pastures and plantations; Frizzo & Vasconcelos, ), we used the values separately in the analyses, assuming independence. We built six candidate models using the same combinations of explanatory variables used as fixed factors in the analyses of the abundance datasets.…”

“…Many individual studies have quantified the ecological importance of scattered trees by comparing the levels of species richness of various groups of biota and the abundance of individual species or groups between areas supporting scattered trees and nearby open areas (Azihou, Kakaï, & Sinsin, ; Brooker, Osler, & Gollisch, ; Hooper, Legendre, & Condit, ). Such investigations have shown that the presence of scattered trees can positively affect the abundance and/or richness of several groups, including plants (Poltz & Zotz, ; Schlawin & Zahawi, ), birds (Barth et al., ; Pizo & Santos, ), bats (Fischer, Stott, & Law, ; Lumsden & Bennett, ), ants (Frizzo & Vasconcelos, ; Oliver, Pearce, Greenslade, & Britton, ), beetles (Oshawa, ), collembolans (Rossetti et al., ) and mites (Brooker et al., ). Conversely, scattered trees may negatively affect the abundance of some species, in particular, herbaceous plants (e.g.…”

Effects of isolation on ant assemblages depend on microhabitat

“…, Campos et al. , b, Frizzo and Vasconcelos , Yanoviak ). This is generally attributed to the physical isolation of tree crowns in space imposed by the phenomenon of crown shyness, a tendency for small gaps to exist among neighboring trees crowns (Ng , Yanoviak ).…”

Effects of land‐use changes on ecosystem services: decrease in ant predation in human‐dominated landscapes in central Brazil

“…Over the past 50 years, the largest and richest savanna region of South America – the Cerrado, in central Brazil – has witnessed a rapid process of conversion into intensive, large‐scale agricultural fields, especially those devoted to the production of soybeans (Ratter et al., ; Myers et al., ). The conversion of large tracts of natural Cerrado vegetation into soybean plantations was found to have strong negative impacts on the diversity of ground‐dwelling ants (Frizzo & Vasconcelos, ; Pacheco et al., ). However, the consequences of such conversion on the predatory activity of ants remain unclear.…”