Past cultivation is a factor driving organization of dry grassland ground-active beetle communities

Abstract

The steppes of the Mediterranean Basin, traditionally managed since ancient times, have been drastically degraded by recent human activities, and are a valuable model to study the impact of present and past anthropogenic disturbances. Climate and edaphic constraints and free sheep grazing have contributed for over 6000 years to the development of a steppe unique to France, but similar to many others in the Mediterranean Basin. This steppe is increasingly threatened by both industrialization and cultivation, and formerly-cultivated plots developed less species-rich vegetation than the steppe. Here, sampling with pitfall traps showed that formerly-cultivated plots hosted more diverse beetle assemblages owing to the presence of ruderal plants, which had greater nutritional value and hosted more phytophagous insects, beetles or other groups, enhancing prey diversity. The steppe had a less species-rich assemblage, but included many species typical of arid areas, some of which are threatened. Former disturbances led to the settlement of ubiquitous species, which increased the overall species richness, but decreased the biological value for conservation. Conservationists have to decide whether they would rather maintain beetle species diversity or biological value.