Influence of agronomic practices, local environment and landscape structure on predatory beetle assemblage

In this study, two main hypotheses were tested: (1) whether landscape structure explains a greater part of the variation in predatory beetle assemblage than agronomic practices and local environment; and (2) whether non-crop areas and landscape heterogeneity have a positive effect on predatory beetle abundance and diversity. Ground and tiger beetles were sampled in ditch borders adjacent to 20 cornfields in 2006 and 2007 in Quebec (Canada). For each site, agronomic practices performed in the border and adjacent field, local border characteristics and landscape cartography (at 200 and 500-m radii) were measured. Compared with agronomic practices and the local environment, landscape structure was globally the main factor driving predatory beetle abundance and diversity, explaining 7.9–24.6% of the variation (unique contribution) depending on the variable and year. In most cases, non-crop areas and landscape heterogeneity had a positive influence on predatory beetle abundance and diversity. Our results showed that variables acting at large scales represent an essential factor influencing predatory beetle assemblage and they validate the importance of conserving non-crop areas and landscape heterogeneity in agricultural landscapes.