Principal response curve analysis of time-dependent multivariate response of arthropod communities to Bt corn

Issue Date

10-2008

Abstract

One of the concerns in the use of transgenic crops is the adverse effects on non-target arthropods. Changes in abundance of non-targets in turn could influence abundance of pests and beneficial organisms through the food web. Thus it is important to look for changes in the whole community including the beneficials. To determine if Bt corn does not reduce the abundance of predatory non-targets nor alter species composition in arthropod communities, a field study using commercial Bt corn farms was conducted in Camarines Sur province from June to September 2007. Arthropod sampling was conducted in separate paired Bt and non-Bt corn sites selected in the farming areas of Tigaon, Ocampo and Sangay. The area of each site was one hectare. Within each site, arthropod sampling was conducted in five 50 m2 quadrants. Sampling was conducted at 6 growth stages of corn. The study was conducted for 3 cropping seasons. Significant differences in arthropod abundance and diversity indices (Shannon, Simpson) between Bt and non-Bt corn fields were determined by repeated measures ANOVA. Significant difference in species composition between Bt and non-Bt corn fields was determined by principal response curve (PRC) analysis. Results of the study showed that the coccinellid beetle Micraspis discolor was the most abundant insect predator in the field. Other predatory arthropods observed in abundance were spiders, the coccinellid. Chilomenes sexmaculatus and the earwig Proreus sp. There was no significant difference in predatory arthropod abundance between Bt and non Bt corn fields. Shannon and Simpson indices revealed no significant alteration of community structure in Bt corn field. PRC analysis also showed that the species composition in Bt corn is similar to that in non-Bt corn field. Taken together, the data suggest that BT corn does not reduce the abundance of M. discolor in the field nor does it alter species composition in arthropod community.

Source or Periodical Title

Philippine Entomologist

ISSN

0048-3753

Volume

22

Issue

2

Page

209

Document Type

Article

Frequency

semi-annually

Language

English

En – AGROVOC descriptors

ARTHROPODA; MAIZE; BACILLUS THURINGIENSIS; TRANSGENIC PLANTS; PLANT PESTS; MULTIVARIATE ANALYSIS

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