The taxonomic level order as a possible tool for rapid assessment of Arthropod diversity in agricultural landscapes

Increasingly intensive agriculture production methods, involving a widespread use of agro-chemicals and the progressive loss of many natural and semi-natural habitats have led to an impoverished wildlife in agro-ecosystems. The awareness of the necessity to conserve, enhance or restore biodiversity in depleted agricultural landscapes has increased in the last decades. Recently new agro-environment schemes and biological compensation programmes have been proposed and they need biodiversity assessment to verify the efficacy of the planned agricultural practices. However, biodiversity assessments often require much effort in terms of time and economical resources. In particular, when analysing Arthropods, one of the groups most commonly used to assess biodiversity in agro-ecosystems, the employment of taxonomists is required for species identification. In this paper we have tried to develop a rapid procedure to assess Arthropod biodiversity in agro-ecosystems. In particular we tested the reliability of two higher taxa as surrogates for Arthropod diversity: order for all the specimens and family for Coleoptera. We collected Arthropods by pitfall traps, both in cultivated and semi-natural micro-habitats, mainly focusing on two different agricultural managements: an intensive wheat field and an experimental one with organic farming and semi-natural habitat conservation. Higher taxa results were compared to those obtained from analysing Carabidae at species level. The use of order level allowed us to clearly distinguish among main land uses on the basis of their faunal composition and diversity. Most prominent, order level analyses gave outcomes comparable to those obtained considering Carabidae species. Conversely, analyses conducted at family level for Coleoptera did not reveal any distinction among land uses. Furthermore, we tested the possibility of shortening the sampling period: about 4 months of surveys seemed to give results very similar to those obtained in a whole year of field activity. We propose our methodology as a possible useful short-cut to assess biodiversity in agricultural landscapes at a local scale. Order surrogacy together with the sampling procedure that we adopted could be seen as a preliminary approach, at least in a first phase of an investigation. This method could be particularly useful when results are required rapidly and in a context of limited financial resources.