Riqueza e composição das comunidades de formigas em quatro formas de cultivo de erva-mate (Ilex Paraguariensis St. Hil., 1822) na Encosta Superior do Nordeste do Rio Grande do Sul

Abstract

In the Rio Grande do Sul State, the maté, Ilex paraguariensis St. Hil. (Aquifoliaceae), is one of the main native components of the mixed ombrophilous forest understory with social-economical and environmental value. The present study aimed at surveying and comparing the ant species richness and composition among four differently cultivated maté fields: native, intercropping system, monoculture and herbicide treated, determining the occurrence and the dominance patterns and the species status. In each fields, ten maté trees were randomly sampled during 12 months using beating tray with a sample effort of 20 beatings per tree. At the same time, 100 sweeps using the entomologic net sampled the vegetation between the maté trees per field. Of the 35 taxa collected, 27 occurred in the native fields, 26 in the herbicide treated fields, 19 in the monoculture and 18 taxa in the mixed culture fields. Fourteen (40.0 %) were common to all cultivation techniques, six (17.1 %) were exclusive to the native fields and four (11.4 %) in the herbicide treated fields. A single exclusive taxon (2.8 %) occurred in the areas of herbicide treatment, mixed culture and monoculture. The native field differed significantly (p=0.031) from the mixed one. The subfamily Myrmicinae was the most representative with 17 genera. The herbicide treated and the monoculture fields had the highest similarity (Sj=71.8 %). Most of the species status was categorized as accidental, dominant and as intermediate. The functional groups distribution presented great similarity among the four ant communities, suggesting that the cultivation form interferes more on the wealth of species than on the functional structure of the ants.