Temporal variation in grasshopper (Orthoptera: Acridoidea) richness, composition, and density in grasslands of the southern Buenos Aires province

• Published in: Revista de la Sociedad Entomológica Argentina 2012-12, Vol.71 (3-4), p.275-288
• Main Authors: Mariottini, Y, De Wysiecki, ML, Lange, CE
• Format: Article
• Language: Spanish
• Subjects: Acridoidea; Orthoptera
• ISSN: 0373-5680

Grasshoppers are among the dominant invertebrate herbivores in most grassland habitats. The economic importance of grasshoppers has been recognized in Argentina since the XIX century, but many aspects of the biology and ecology of most species remain unknown. The main objective of this study was to determine how grasshopper species richness, composition, and density varied among characteristic plant communities during five successive seasons (2005-06 to 2009-10) in grasslands of the southern Buenos Aires province, an area historically affected by these insects. Twenty two species were collected. Grasshopper species richness was similar between different plant communities and showed a significant decrease in the final year of sampling. The overall density increased significantly in all plant communities during the study, reaching outbreak levels in the last two seasons. Density was over eight times higher in 2009-10 than in 2005-06. The greatest contribution to the increase in density observed was by Dichroplus maculipennis(Blanchard) and Borellia bruneri(Rhen). Dichroplus maculipennis re-emerged as the most serious grasshopper pest in the Pampas, developing an outbreak of historical magnitude that included high densities of up to 75 ind/m super(2).Original Abstract: Los acridios figuran entre los invertebrados herbivoros dominantes en la mayoria de los sistemas de pastizal. Si bien, en Argentina, la importancia economica de estos insectos ha sido reconocida desde el siglo XIX, aum se desconocen aspectos importantes de la biologia y ecologia de la mayoria de las especies. El objetivo principal de este estudio fue determinar como la riqueza de especies, la composicion y la densidad de acridios variaron en las comunidades vegetales mas caracteristicas del Sur de la provincia de Buenos Aires, durante cinco temporadas sucesivas (2005-06 hasta 2009-10), un area historicamente afectada por estos insectos. Se colecto un total de 22 especies. La riqueza de acridios fue similar entre las diferentes comunidades vegetales, observandose una disminucion significativa de la misma durante la ultima temporada de muestreo. La densidad total de acridios aumento significativamente en todas las comunidades vegetales durante el estudio, alcanzando niveles de explosion poblacional ("outbreak") en las ultimas dos temporadas. En la de 2009-10, la densidad fue ocho veces mayor que en 2005-06. Las especies que mas aportaron a este aumento en la densidad fueron Dichroplus maculipenni