COMMUNITY AND ECOSYSTEM ECOLOGY Spatial and Temporal Variation in Species Composition, Diversity, and Structure of Mediterranean Dung Beetle Assemblages (Coleoptera: Scarabaeidae) Across a Bioclimatic Gradient IMEN LABIDI, 1 FAI ¨ EK ERROUISSI, 1,2 AND SAI ¨ D NOUIRA 3 Environ. Entomol. 41(4): 785Ð801 (2012); DOI: http://dx.doi.org/10.1603/EN11278 ABSTRACT Both spatial (bioclimatic stages) and temporal (seasons) analyses were contemplated to estimate the inßuence of Mediterranean bioclimate on dung beetle assemblageÕs distribution. Insects were pitfall trapped once per season from 2008 to 2009 at eight bioclimatic sites from north to south of Tunisia. In total, 3,278 specimens and 39 species (18 Aphodiinae and 21 Scarabaeinae) were collected and the completeness of sampling was of 76.81%. Along the bioclimatic gradient species richness of these two families were of the same order (Scarabaeinae/Aphodiinae ratio 1.16). The highest value of species richness occurs in subhumid site (27 species) and the lowest in the arid sites (5 species). More beetles were captured in spring and few beetles in autumn. However, more Scarabaeinae were captured in summer and more Aphodiinae in winter. Humid and subhumid sites were more diverse with high temporal turnover and, 80% of species occur in this area of the northÐwest of Tunisia. Conversely, the arid sites have the lowest values of - and -diversity. The highest spatial turnover occurs between semiarid middle and semiarid inferior. Several factors could explain these results such as the soil nature, the geographical position, and latitude. Multivariate analyses showed that: 1) latitude greatly inßuenced the assemblage organization than bioclimate; 2) spatial factors (soil, bioclimate, latitude, altitude, marine inßuence) have greater effect than temporal factors (season); and 3) the Tunisian Dorsale is a stronger determinant where it act as a barrier or a Þlter that limit the colonization of arid sites by dung beetles and species occurred in these sites were those locally abundant an largely distributed. Results indicate that there were no spatio-temporal patterns accord- ing to bioclimate, but the inßuence of local and regional factors predominates on the dung beetle assemblages distribution. KEY WORDS Mediterranean bioclimate, dung beetle assemblages, abiotic factors, spatial scale, temporal scale Study of the distribution patterns of living organisms and of the factors that they are driven by is a central theme that has stimulated scientiÞc research during recent decades (Huston 1994). The large number of theories proposed to explain spatio-temporal patterns of biodiversity at different scales attests to this inter- est, while it also underlines the complexity of the ecological processes involved. Many different vari- ables can inßuence current species distribution (He- glund 2002, Huston 2002), especially in the case of rare and endemic species (Gaston 1994), depending on the biogeographical region studied and the scale consid- ered. Local diversity is generated and maintained by a complex of ecological factors such as predation, competition, food availability, and so forth. Whereas, regional diversity is determined by other factors like altitude, latitude, climatic variability, age of ecosys- tem, spatial heterogeneity, and so forth (Begon et al. 1986, Fjeldså and Lovett 1997). Dung beetles are known to be of ecological impor- tance in terrestrial habitats. Their role in dung decay and increasing soil fertility is well established (Bor- nemissza 1970). By burying and eating dung, this group of insects increases the rate of soil nutrient recycling and decrease parasites like helminth and pest such as Diptera (Halffter and Matthews 1966, Fincher 1981). Dung Beetle communities comprise species with special ecological requirements because of the ephemeral and patchy nature of dung (Mohr 1943, Hanski 1987). This group includes three families: Scarabaeinae, Aphodiinae, and Geotrupinae and most of them are attracted to fresh herbivore and omnivore dung. Geotrupinae and most of Scarabaeinae species are tunnelers and developed a complex nesting be- haviors that enhance dung utilization and secure food 1 UR Biodiversite ´ et Biologie des Populations (05/UR/09-10), Uni- versite ´ Tunis El Manar, Institut Supe ´ rieur des Sciences Biologiques Applique ´ es de Tunis, 9 Avenue Zohaõ ¨r ESSEFI, TN-1006 Tunis, Tu- nisie. 2 Corresponding author, e-mail: Faiek.Rouissi@issbat.rnu.tn. 3 UR Biodiversite ´ et Biologie des Populations (05/UR/09-10), Uni- versite ´ Tunis El Manar, Faculte ´ des Sciences de Tunis, Campus Uni- versitaireÐTunis, 1060 Tunisie. I. Labidi and F. Errouissi contributed equally. 0046-225X/12/0785Ð0801$04.00/0  2012 Entomological Society of America Downloaded from https://academic.oup.com/ee/article/41/4/785/442901 by guest on 31 January 2023