The effect of landscape structure on two species of different trophic levels in an arid environment

Abstract

Insect species of different trophic level will respond differently to landscape configuration. Objective: In this context we explore the way landscape structure affects the distribution and abundance of the whitefly Siphoninus phillyreae and its predator Clitostethus arcuatus in olive orchards. Methods: Adult individuals of these two species were collected using sticky traps placed in 12 olive host patches in Argentina. Host patches were detected and quantified using Landsat 5 TM images. Different landscape metrics were estimated for the study area land covers. PLSR analysis techniques were employed to relate the mean abundance of the studied species and the landscape measures. Results: The Landsat land use estimations showed that most of the vegetation is limited to particular irrigated spots or urban areas. 89 % of the land cover is exposed soil, 10 % is xerophytic vegetation, 0.56 % is introduced urban vegetation and 0.31 % is occupied by olive orchards. S. phillyreae was positively affected by total area of olive orchards, followed by total area of urban vegetation, and negatively affected by the perimeter of olive focal patch and the proximity of other urban vegetation patches. C. arcuatus was positively affected by the perimeter of the host patch, the total area of olive orchards and the mean proximity of urban vegetation patches. Conclusion: We concluded that although the total area of the herbivore host was the most influential variable affecting the two species, each of them was affected in different way by other landscape elements.