Resource quality and the colonisation and succession of coprophagous dung beetles

In order to examine the degree of resource selectivity in a north temperate dung beetle assemblage and to identify major parameters that influence suc h selectivity, the occurrence of adult dung beetles (Aphodius, Geotrupes an d Sphaeridium) in up to five different types of dung over a period of up to 25 d was examined in a series of field experiments using standardised dung pats. There were significant physical and chemical differences in dung qua lity between dung types and over time during succession. Dung beetle specie s showed distinct preferences for particular types of dung which were gener ally similar in data sets from both pitfall traps and dung pat samples. Spe cies also showed distinct patterns of successional occurrence. Ordinations produced by Canonical Correspondence Analysis, based on species occurrences in dung types and over time, usually selected dung pat age as the most imp ortant environmental variable influencing dung beetle assemblages. Dung qua lity parameters contributed a significant element of structure to the speci es ordinations but ordinations using dung types or dung quality parameter v alues as the environmental variables were very similar in terms of sample a nd species placement within the ordination for each data set. Most importan tly the CCA ordinations clearly grouped species according to their breeding behaviour. Early-successional species laid eggs in the soil, or in silken egg cocoons, which allowed them to exploit wet dung. Mid and late-successio nal species laid eggs in the dung pat; late-successional species could expl oit normally wetter dung types than mid-successional species, probably due to increased crust formation and drying as the dung pat ages. Thus, species appear to be differentially adapted to exploit varying types of dung micro habitats. Therefore, where two or more species of large herbivores are pres ent, dung quality preferences probably constitute an important niche dimens ion.