Rolling in the deep: morphological variation as an adaptation to different nesting behaviours of coprophagous Scarabaeoidea

In a local community of closely related species exploiting the same food source its abundance as a strong selective pressure directs the ecological niche partitioning that can be mirrored in different life-history traits. In dung beetles (Scarabaeoidea) that feed on patchy and timely limited excrements of large vertebrates, competition is mirrored in their specific adaptations in behaviour and morphology. In a local community from Slovenia, we sought for a morphological variation of 36 morphological traits in 28 dung beetle species belonging to two families (Scarabaeidae, Geotrupidae) that can be linked to their evolutionary background (family, subfamily, tribe, species) and their life style (i.e. nesting behaviour: rollers, dwellers, tunnelers). We showed that morphological traits specific for each ecomorphological group reflect the functional adaptations to their life strategies of nesting behaviour, but also phylogenetic (family, subfamily) membership. The unique combinations of evolutionary background and same life styles within/among different phylogenetic lineages (families, subfamilies, tribes) revealed the morphological traits that are a result of different evolutionary scenarios (convergences/divergences between members of different/same phylogenetic lineage with same/different life nesting behaviour). At least four (Aphodiinae – dwellers, Geotrupinae – tunnelers, Scarabaeinae – tunnelers, Scarabaeinae – rollers) ecomorphological groups were recognised from a local community, but an existence of a possible fifth group represented by Coprimorphus scrutator of Aphodiinae indicates that the ecomorphological differentiation exists also at a smaller scale. Finally, by the quantification of gaps in morphological space between the pairs of defined ecomorphological groups we showed that the guild membership overrides the family/subfamily membership in a light of ecomorphological adaptations to specific nesting behaviours.