Abstract

WYSIECKI, María Laura de; TORRUSUI, Sandra  and  CIGLIANO, María Marta. Grasshopper (Orthoptera: Acridoidea) community structure in Benito Juárez county, in outhern Buenos Aires province, Argentina. Rev. Soc. Entomol. Argent. [online]. 2004, vol.63, n.3-4, pp.87-96. ISSN 0373-5680.

The structure of grasshopper communities was studied at different sites in Benito Juárez county, Buenos Aires province, Argentina, over a six-year period (1997-2002). The sites were classified into five categories of disturbance: native grasslands, halophilous communities, pastures, moderately and highly disturbed pastures. A total of 23 grasshopper species was collected. Melanoplinae was the most abundant subfamily in all sites, except for halophilous communities that were characterized by the presence of one Acridinae species, Covasacris pallidinota (Bruner). Average species richness per site and per year, ranged from 2.10 ± 0.60 species in moderately disturbed pastures to 6.20 ± 0.58 species in halophilous communities. Cumulative species richness was: 17 in native grasslands, 14 in halophilous communities, 19 in undisturbed pastures, 18 in moderately disturbed pastures and 14 in highly disturbed pastures. Mean density was significantly higher in 2001 and 2002 than in the remaining years. The most abundant species were Dichroplus pratensis Bruner and Dichroplus elongatus Giglio-Tos in native grasslands and highly disturbed pastures; C. pallidinota in halophilous communities and D. elongatus - Scotussa lemniscata (Stål) in undisturbed and moderately disturbed pastures. Along the study, the taxonomic structure of the grasshopper assemblages was significantly constant in native grasslands, halophilous communities and undisturbed pastures. The pattern of species distribution showed few species widely or intermediately distributed, whereas numerous species were rare. Among the 23 species collected, D. elongatus was the most broadly distributed of all. Historically, Dichroplus maculipennis (Blanch.) has been known as the most conspicuous species in the studied area. However, our results suggest that nowadays D. elongatus is the most common species. Among other factors, climate changes, insecticidal treatments against grasshoppers or other pests, and changes in the land use might be involved in such change in dominance.

Keywords : Grasshoppers; Community structure; Grasshopper density; Temporal variation; Dichroplus elongatus.

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