Diversity and structure of dung beetle assemblages under two contrasted habitats in Tunisia: oases vs. humid pastures

Abstract

Dung beetles were used as an indicator group to identify whether oases play an important role as a refuge for biodiversity under harsh environmental conditions in Mediterranean ecosystems. Here, we provide a comparative framework for analysing seasonal changes in species composition, abundance and diversity in two local dung beetle assemblages trapped at two contrasted habitats. Using pitfall traps, we collected 3585 dung beetle specimens representing two subfamilies, 15 genera and 28 species (11 Aphodiinae and 17 Scarabaeinae). We trapped 24 and 10 species in humid pasture and oases habitats, respectively. Aphodiinae was more abundant in humid habitats, while Scarabaeinae dominated in oases. Abundance of the six common species was higher in oases than in humid pastures. Multivariate analyses showed that there were two different faunas functioning differently. The humid pastures assemblage showed net temporal segregation with high alpha and beta (temporal turnover) diversities, which may be the result of a well-established community adapted to local climatic conditions. Furthermore, the contrast generated by the oases in the desert environment has allowed for widely distributed and some non-desert-adapted species to be more abundant. The harsh conditions of the desert environment have led to the development of an impoverished fauna with lower temporal heterogeneity (low temporal beta diversity). Evenness, core species and groups were lower under oases conditions than compared with humid habitats. This study demonstrates that humid pastures in Tunisia have richer dung beetle assemblages than oases, but with comparison to surrounded area, oases may represent a refuge for some species and an important conservation area for dung beetles living in harsh conditions in desert environments.