Influence of weather variables and plant communities on grasshopper density in the Southern Pampas, Argentina

María Laura de Wysiecki1a, Marcelo Arturi2b, Sandra Torrusio3c, María Marta Cigliano4d*

1 Centro de Estudios Parasitológicos y de Vectores (CEPAVE), (CCT-La Plata- CONICET- UNLP), Calle 2 n° 584, 1900 La Plata, Argentina
2 LISEA, Facultad de Ciencias Agrarias y Forestales, UNLP. Diagonal 113 n° 469, 1900 La Plata, Argentina
3 Facultad de Ciencias Naturales y Museo, Avda 122 y 60. 1900 La Plata, Argentina.
4División Entomología, Museo de La Plata, Paseo del Bosque s/n. 1900 La Plata, Argentina

Abstract

A study was conducted to evaluate the influence of weather (precipitation and temperature) and plant communities on grasshopper density over a 14-year period (1996-2009) in Benito Juárez County, Southern Pampas, Argentina. Total density strongly varied among plant communities. Highest values were registered in 2001 and 2003 in highly disturbed pastures and in 2002 and 2009 in halophilous grasslands. Native grasslands had the lowest density values. Seasonal precipitation and temperature had no significant effect on total grasshopper density. Dichroplus elongatus (Giglio-Tos) (Orthoptera: Acridoidea), Covasacris pallidinota (Bruner), Dichroplus pratensis Bruner, Scotussa lemniscata Stål, Borellia bruneri (Rehn) and Dichroplus maculipennis (Blanchard) comprised, on average, 64% of the grasshopper assemblages during low density years and 79% during high density years. Dichroplus elongatus, S. lemniscata and C. pallidinota were the most abundant species in 2001, 2002 and 2003, while D. elongatus, B. brunneri and C. pallidinota in 2009. Dichroplus elongatus and D. pratensis, mixed feeders species, were positively affected by summer rainfall. This suggests that the increase in summer precipitation had a positive effect on the quantity and quality forage production, affecting these grasshopper populations. Scotussa lemniscata and C. pallidinota were negatively affected by winter and fall temperature, possibly affecting the embryonic development before diapause and hatching. Dichroplus elongatus and D. pratensis were associated with highly disturbed pastures, S. lemniscata with pastures and B. bruneri and D. maculipennis with halophilous grasslands. Covasacris pallidinota was closely associated with halophilous grasslands and moderately disturbed pastures. Weather conditions changed over the years, with 2001, 2002 and 2003 having excessive rainfall while 2008 and 2009 were the driest years since the study started. We suggest that although seasonal precipitation and temperature had no significant effect on total grasshopper density, these weather variables and plant communities had differential influence on the dominant grasshopper species.

Keywords: Acrididae, community ecology, precipitation, vegetation, pampas

Correspondence: a mlw@fcnym.unlp.edu.ar, b talares@agro.unlp.edu.ar, c torrusio@retina.ar, d* cigliano@fcnym.unlp.edu.ar, *Corresponding author

Editor: Tugrul Giray was editor of this paper.

Received: 9 December 2008 | Accepted: 14 July 2011 | Published: 25 August 2011

ISSN: 1536-2442 | Volume 11, Number 109

de Wysiecki ML, Arturi M, Torrusio S, Cigliano MM. 2011. Influence of weather variables and plant communities on grasshopper density in the Southern Pampas, Argentina. Journal of Insect Science 11:109 available online: insectscience.org/11.109


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