Abstract
Ants are the most abundant group of soil arthropods in olive groves where they are involved in various trophic relation- ships of great importance for crops. The system of soil management is one agricultural practice that has a great effect on ants, so the objective of this study was to compare ant populations in organic olive orchards with a ground cover of natural vegetation and others where this natural vegetation is mechanically removed at the beginning of June. Ants were sampled using pitfall traps at 14, 30, 70 and 90 days after the removal of the ground vegetation. Overall, ant biodiversity did not change. However, changes were observed in the abundance of ant species, in particular, in those species that build shallow nests in the soil, both between the rows of trees and under the canopy of olive trees. In contrast, deep nesting species, such as Messor barbarus, were not affected. The response also dif- fered between the various genera: the abundance of Cataglyphis increased, due to there being more of the species C. rosenhaueri, while there was a significant fall in Aphaenogaster, due to the decline in abundance of A. senilis. Thirty days after the removal of vegetation, the response of most of the genera was clearly noticeable, due to the increased activity of workers, and in some cases there were still differences after 90 days.
Highlights
Ants make up a large proportion of the arthropod fauna in many land ecosystems, where they play a key role in determining the structure and functioning of local communities (Hölldobler & Wilson, 1990)
They are often used as indicators, because they show a rapid response to environmental changes, are abundant and diverse in many environments and sampled, and serve a wide variety of ecosystem functions (Peck et al, 1998; Andersen, 1990; Alonso & Agosti, 2000)
Ants play an important role within the arthropod community in olive orchards as they consume larvae of pests, such as Prays oleae (Lepidoptera: Plutellidae) (Arambourg, 1986; Morris et al, 2002; Pereira et al, 2002), but can have harmful effects on natural enemies because ants eat the eggs of the predator Chrysoperla carnea (Neuroptera: Chrysopidae) (Morris et al, 1998) and the parasitoid Trichogramma cacoeciae (Hymenoptera: Trichogrammatidae) used for the biological control of Prays oleae (Pereira et al, 2004)
Summary
Ants make up a large proportion of the arthropod fauna in many land ecosystems, where they play a key role in determining the structure and functioning of local communities (Hölldobler & Wilson, 1990). They are often used as indicators, because they show a rapid response to environmental changes, are abundant and diverse in many environments and sampled, and serve a wide variety of ecosystem functions (Peck et al, 1998; Andersen, 1990; Alonso & Agosti, 2000). In relation to the intensity of management in conventional olive farming, in which synthetic pesticides and fertilizer are allowed and the soil is frequently deeply ploughed, the abundance and richness of ant species is lower than on land organically farmed (Redolfi et al, 1999; Santos et al, 2007b)
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