Functional biodiversity in the agricultural landscape: relationships between weeds and arthropod fauna

We reviewed studies aimed at understanding functional relationships between weeds and arthropods in agroecosystems as influenced by biodiversity at different scales, with the main goal of highlighting gaps in knowledge, research methods and approaches. We first addressed: (i) the regulation of arthropod communities by weed diversity at genetic, species and habitat levels, (ii) the regulation of weed communities by arthropods through seed predation and dispersal and (iii) below-ground weed-insect interactions. We then focussed on methodologies to study weed–arthropod interactions in agricultural landscapes and discuss techniques potentially available for data analysis and the importance of joint weed–arthropod trend detection. Lastly, we discuss the implications of research findings for biodiversity conservation policies (agri-environmental schemes) and suggest some priorities for future work. Results showed that to date research has largely ignored weed–arthropod interactions in agricultural landscapes. No information is available on the role of weed genetic diversity as driver of weed–arthropod interactions, whereas studies on effects of species and habitat diversity often lack a functional perspective and/or a spatial component. Also, information on how management of the wider agricultural biotope might express positive weed–arthropod functional interactions is scarce. Another area worth being explored is the relationship between weed-leaf/root herbivores and beneficial arthropods. Tools for spatial data analysis might be useful for elucidating weed–arthropod interactions in agricultural landscapes, but some methodological aspects, e.g. the definition of the most appropriate experimental design and sampling scale/frequency, must be refined. New studies on weed–arthropod interactions should encompass an explicit spatial component; this knowledge is particularly important for improving IPM/IWM systems and designing more targeted agri-environmental schemes.